Common rail fuel system
MG Rover
Group
Electronic Diesel
Control
© MG Rover Group 2001
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any
form, electronic, mechanical, recording or other means without prior written permission from MG Rover Group.
1
Common rail fuel system
History
A research company by the name of Elasis in Naples, developed common rail
technology.
In 1993 the Italians produced a prototype of their new fuel injection system.
Problems with the tolerances of the injectors stopped the planned volume
production and prompted the search for a partner at the turn of the year
1993/94. Bosch bought the patents and took over Elasis. Bosch presented the
new system on the market one year earlier than any other manufacturers.
Introduction
In conventional systems, pressure generation is coupled to injection volume
preparation. This has the following consequences for the injection
characteristics:
• The injection pressure increases as the speed and volume increase
• The injection pressure increases during actual injection
Consequently;
• small injection volumes are injected at lower pressures
• the peak pressure is more than twice as high as the mean injection pressure
The peak pressure governs the load on the components of an injection pump
and the pump drive.
On the other hand, the mean injection pressure is important for the quality of
fuel-air mixture in the combustion chamber.
Requirements
Increasingly stringent regulations governing exhaust and noise emissions and
the demand for lower fuel consumption mean that the injection system of a
diesel engine must consistently fulfill new requirements.
• Highest possible metering accuracy over the entire service life
• Pre-injection and main injection
• It is possible to independently determine the injection pressure and injection
volume for every operating point of the engine which gives additional degree
of freedom for ideal mixture preparation
• The injection volume and pressure should be as low as possible at the start
of injection to prevent ignition delay between the start of injection and the start
of combustion to obtain smoother engine operation (pre-injection).
Functional principle
The Rover 75 is the very first Rover diesel engine to be equipped with a highpressure accumulator fuel injection system (common rail). With this new fuel
injection process, a high-pressure pump delivers a uniform level of pressure
to the shared fuel line (the common rail) which serves all the fuel injectors.
Pressure develops to an optimum level for smooth operation. This
2
means that each injector nozzle is capable of delivering fuel at pressures of
up to 1350 bar.
The common rail system disconnects fuel injection and pressure generation
functions. Fuel injection pressure is generated independently of the engine
speed and fuel injection volume and The fuel injection timing and fuel volume
are calculated individually in the EDC control unit and delivered to each
engine cylinder by the injectors, each of which is actuated by energising the
appropriate solenoid valve.
Advantages:
1.
2.
3.
4.
5.
6.
7.
Fuel injection at exactly the right moment
Precisely metered fuel quantity
Constant high pressure
Fuel consumption optimised
Emission reduction
Very smooth engine operation
Pre-injection:
• The ignition delay at the point of main injection is shortened
• Combustion pressure peaks are reduced (Smoother combustion)
• Emissions are reduced
8. Main injection:
• Variable operating pressure according to engine demands
• The injection pressure remains constant over the entire injection period
thus enabling more accurate volume metering.
• The main injection is responsible for torque generation is made available
in the rail (high pressure fuel accumulator) for injection to the cylinders.
System structure
The fuel system is divided into 2 sub-systems:
• Low-pressure system
• High-pressure system
The low-pressure system features the following components:
•Fuel tank
• Advance fuel pump (in tank)
• Outlet protection valves
• In-line electric fuel pump
• Fuel filter with inlet pressure sensor
• Pressure relief valve (low pressure system) and in the fuel return line:
• Fuel cooling control (bimetal valve)
• Fuel cooler
3
The high pressure system features the following components:
• High-pressure fuel pump
• Fuel high-pressure accumulator (rail)
• Pressure control valve
• Rail pressure sensor
•Injectors
Diesel fuel system
The diesel fuel system consists of an extra underbonnet fuel pump and fuel
return lines. Also, a diesel cooler is fitted to the fuel tank return line.
The right hand venturi on the diesel system is fed directly from the pump in
the tank and a tee- joint feeds the venturi in the opposite side. Unlike the intank filter fitted to petrol derivatives, the diesel filter is fitted externally to the
tank in an underbonnet location.
The extra pump is fitted before the fuel filter and increases the pressure to
assist the fuel through any potential blockage of the filter during cold starts.
The extra pump helps to ensure all engine fuelling requirements are satisfied
in all conditions.
A pressure regulator is located after the filter and relieves fuel into the
secondary pump feed.
4
Fuel leaves the tank from an outlet on the top of the filter adapter unit and is
transferred to a secondary low-pressure fuel pump. Both the primary and
secondary low-pressure fuel pumps are controlled by the ECM via a single
relay. When the ignition is switched to position II, the fuel pump relay is
energised for up to 20 seconds, this operates the low-pressure fuel pumps to
build up approximately 2.5 bar line pressure supply to the main fuel filter and
high-pressure fuel pump.
The spill return from the high-pressure pump and injectors is returned to the
tank via a connection to the right hand section of the fuel tank. The excess
fuel flow divides into two at a tee connection, one output passes fuel through
a venturi which draws fuel from the left side of the tank and delivers it to the
right side of the tank. The other output passes fuel through a venturi which
draws fuel from the right hand side of the tank and delivers it to the swirl pot.
This arrangement ensures that the left side of the tank is scavenged into the
right side, and the fuel level in the swirl pot is always maintained regardless of
vehicle movement.
Each side of the fuel tank contains a sender unit to detect fuel level. The
senders are wired in series to the instrument pack. The instrument pack
utilises an algorithm to calculate fuel level from both level sender units.
The ECM detects pressure in the low-pressure side of the system via a
pressure sensor installed in the fuel filter head. The sensor output is required
by the ECM to determine if the high-pressure fuel pump is receiving sufficient
pressure. If the ECM detects insufficient inlet pressure to the high-pressure
fuel pump, it will reduce engine speed and fuel rail pressure accordingly to
prevent damage to the high-pressure fuel pump.
Comparison of a common rail system to a conventional system
Conventional injection characteristics
In conventional injection systems, such as the use of distributor and in—line
injection pumps, only a single injection takes place. Pressure generation is
coupled to injection volume preparation. This has the following consequences
for the injection characteristics:
• The injection pressure rises as the engine speed and injection quantities
increase
• The injection pressure increases during injection
As a result:
• At low pressures small quantities are injected
• The peak pressure is more than twice the average fuel injection pressure
Peak pressure determines the load which can be applied to the components
of an injector pump and its drive unit.
The average injection pressure is, however, important for the quality of the
fuel/air mixture in the combustion chamber.
5
Common rail injection characteristics
Common rail fulfils the following demands:
• It is possible to independently determine the injection pressure and injection
volume for every operating point of the engine which gives an additional
degree of freedom for the ideal mixture preparation
• After the start of combustion, it should be possible to select the injection
pressure throughout the entire period of injection
These requirements have been fulfilled in the common rail accumulator
injection system with preliminary and main injection. Noise and vibration
characteristics are affected to a large extent by the degree of combustion.
Therefore, a carefully planned adaption of fuel injection has taken on an
important role.
The influencing of the engine combustion takes place by means of a
preliminary injection in the common rail system. This makes disturbance-free
combustion at lowest noise levels possible.
Because of its modular design the system can be easily matched to various
engines; the conventional injection nozzle holder can be substituted by the
common rail injectors and the high pressure pump can be mounted on the
engine. The transition from conventional system to a common rail system can
thus be made quite easily. A comparison between the conventional and
common rail component structure can be seen in table ’Component
comparison.
DESCRIPTION
COMMON RAIL SYSTEM
CONVENTIONAL SYSTEM
High Pressure Generation
High Pressure Pump
Pressure Distribution
Supply Reservoir
Thick High Pressure Lines
Rail
Distributor Type Injection
Pump
High Pressure Lines
N/A
Injection
Injector - Electronic
Injector Nozzle – Mechanical
Data for the common rail fuel system can be seen in table ’Common rail
technical data.
DESCRIPTION
TECHNICAL DATA
Pressure
250 – 1350 Bar
Injection Begin
Pre-Injection
Main-Injection
Pump Speed
Max 60 Btdc
Max 25 Btdc
0.75 X Engine Speed
Injection Quantity
1 – 80 Mm3 Per Stroke
Max Delivery Volume
240 Litres Per Hour
6
Common rail components
The following describes the functionality of the components that form the
common rail fuel system.
Fuel tank
The M47R diesel is fitted with a blow moulded plastic saddle tank with plastic
underfloor fuel and vent lines . The fuel lines are covered with a flame
retardant material.
A submersible, low-pressure electric fuel pump is located in the right hand
section of the fuel tank, this pump is called the primary low-pressure pump.
The primary low-pressure pump draws fuel from the swirl pot and delivers it to
a filter unit adapter mounted in the left hand section of the fuel tank. The
adapter unit contains a pressure regulator which is calibrated to 3.6 bar, this
will not open during normal operation of the system. The tank has a capacity
of 66 litres gross (64.8 litres useable) and is secured to the vehicle foreplay
using a H frame strap assembly. The filler is located on the right hand side
(HRS.) of the rear wing panel. The tank is protected from the heat of the
exhaust system by a reflective metallic heat shield.
7
Electrical fuel pump
The electrical fuel pump is located inside the fuel tank in the right-hand side.
The electrical fuel pump transports fuel from the swirl pot towards the engine
and operates the level control venturis in the left and right sides of the tank.
Both venturis deliver fuel to the swirl pot in the right-hand side of the tank.
The electrical fuel pump is activated by the ECM via the electrical fuel pump
relay
.
In-line electrical fuel pump (medium pressure)
The in-line electrical fuel pump is located in the inlet line and has the task of
providing the HPP with an adequate amount of fuel:
• In every operating condition
• At the required pressure
• Across the entire service life
8
The in-line electrical fuel pump is also activated by the ECM via the same
electrical fuel pump relay.
High-pressure pump
The HPP is located at the front left side of the engine, the same position as a
distributor-type fuel injection pump.
The HPP is the interface between the low-pressure and the high-pressure
sections. It has the task of ensuring that there is always enough fuel delivered
at a sufficient pressure in every operating mode across the entire service life
of the vehicle. This includes the delivery of spare fuel, required for a rapid
start and pressure increase in the rail.
9
Fuel is delivered via the filter to the HPP intake and the safety valve (9)
situated behind it. It is forced through the throttle bore into a low-pressure duct
(8).
This duct is connected to the lubrication and cooling circuit of the highpressure pump. It is therefore not connected to an oil circuit.
The drive shaft (1) is driven via the chain drive at three quarters engine
speed.
It moves the three pump pistons (3) up and down with its eccentric cam (2),
depending on the cam shape.
If the pressure in the low pressure duct exceeds the opening pressure of the
suction valve (6) (0.5 -1.5 bar), the advance delivery pump can force fuel into
the element chamber where the pump piston moves downwards (suction
stroke). If the dead-centre point of the pump piston is exceeded,
then the intake valve closes. Fuel in the element chamber (4) can no longer
escape. It is then compressed in the intake line by the delivery pressure.
10
The accumulating pressure opens the exhaust valve (5) as soon as the
pressure in the rail is achieved. Compressed fuel enters the high-pressure
system.
The pump piston delivers fuel until the upper dead-centre point is reached
(delivery stroke).
Pressure then falls again, which closes the outlet valve. The remaining fuel is
no longer subject to pressure. The pump piston moves downwards.
If the pressure in the element chamber falls below the pressure in the lowpressure duct, then the intake valve opens again. The whole process is
repeated from the beginning.
The high-pressure pump constantly generates the system pressure for the
high-pressure rail. The pressure in the rail is determined by the pressure
control valve.
Since the high-pressure pump is designed for large delivery quantities, there
is an excess of compressed fuel when the vehicle is idling or only subject to
partial load. Since the compressed fuel is no longer subject to pressure once
the excess fuel flows away, the energy generated by the compression is lost
and/or heats the fuel.
This excess delivered fuel is returned to the tank via the pressure control
valve and the fuel cooler.
Pressure control valve
The pressure control valve is located at the back of the high-pressure pump
The pressure control valve has the task of setting and maintaining the rail
pressure according to the load status of the engine.
• If the rail pressure is too high, the pressure control valve opens, which
enables some of the fuel to pass from the rail to the fuel tank via a collector
line
• If the rail pressure is too low, the pressure control valve closes and seals the
high-pressure side from the low-pressure side
11
Fuel high-pressure accumulator (rail)
The fuel high-pressure accumulator (rail) is located beside the cylinder head
cover
High pressure fuel rail
In the fuel high-pressure rail, the fuel is subjected to high pressure and
delivered (accumulated) for injection.
This accumulator, which is used by all cylinders (where the name common rail
originates from), maintains its internal pressure at the near constant value,
even when handling larger quantities of fuel. This ensures that the injection
remains at a near constant when the injector is opened.
Fluctuations in pressure, resulting from the pump delivery and injection, are
dampened by the accumulator volume.
The fuel high-pressure rail is essentially a thick walled pipe with connections
for lines or sensors.
On the M47R, the fuel high-pressure sensor is located at one end of the rail.
The fuel high-pressure rail is continuously supplied with fuel from the highpressure pump. Fuel is delivered from this rail to the injectors via the injector
connector lines. The rail pressure is set via the pressure control valve.
The volume present in the rail is constantly filled with the pressurised fuel.
The spring action brought about by the high pressure is used to create an
accumulator effect.
If fuel is removed from the rail for the purpose of injection, the pressure in the
high-pressure rail remains at a near constant. Fluctuations in pressure
created by the cycled supply of the high-pressure pump are damped and/or
compensated.
12
Rail pressure sensor
The rail pressure sensor is screwed onto the end of the rail
The rail pressure switch must measure the current fuel pressure in the rail;
• with sufficient accuracy and
• in a suitably short time
It must then supply a voltage signal to the control unit. The signal corresponds
to the level of pressure present.
Injectors
The injectors are arranged in the central area above the combustion
chambers in the cylinder head
The injectors are held in the cylinder head with what is known as clamping
shoes. The common rail injectors are therefore suited for installation into
existing directly injected diesel engines without any major alterations required.
The injector needle has a single guide so that the risk of needle friction can be
prevented at a design level.
The injector can be divided into a variety of function blocks:




Hole nozzle with injector needle
The hydraulic servo system
Solenoid valve
Connections and fuel channels
13
Engine Coolant Temperature (ECT) sensor
The ECT sensor is located in the engine block at the front of the engine. It
provides the ECM with engine coolant temperature information. The ECM
uses this ECT information for the following functions:





Fuelling calculations.
Temperature gauge.
To limit engine operation if coolant temperature is too high.
Cooling fan operation.
Glow plug operating time.
The ECM ECT sensor circuit consists of an internal voltage divider circuit
incorporating an external negative temperature coefficient thermistor. As
temperature rises, the resistance in the thermistor decreases, as temperature
decreases, the resistance in the sensor increases.
The output of the sensor is the change in voltage as the thermistor allows
more current to pass to earth according to the temperature of the coolant. The
ECM compares the signal voltage to stored values and compensates fuel
delivery to ensure optimum driveability at all times. The engine will require
more fuel when it is cold to overcome fuel condensing onto the cold metal
surfaces inside the combustion
chamber. To achieve a richer air/fuel ratio the ECM extends the injector
opening time. As the engine warms up the air/fuel ratio is leaned off.
The inputs and outputs for the ECT are a reference voltage and an earth
return circuit, both provided by the ECM. The ECT signal is measured at the
ECM.
In the event of an ECT sensor signal failure any of the following symptoms
may be observed:





Difficult cold start.
Difficult hot start.
Drivability concerns.
Instrument pack temperature warning illuminated.
Temperature gauge reading does not accurately represent the coolant
temperature.
In the event of ECT signal failure the ECM applies a default value of -10 °C
before start up & 80 °C (176 °F) when engine running for fuelling purposes.
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The ECM will also run the cooling fan when the ignition is switched on to
protect the engine from overheating.
Crankshaft Position (CKP) sensor
The CKP sensor is located in the engine block, beneath the starter motor, with
its tip adjacent to the outer circumference of the crankshaft reluctor ring.
The CKP sensor works on the variable reluctance principle. This uses the
disturbance of the magnetic field which is set up around the CKP sensor,
caused by the rotation of a reluctor ’target’ attached to the crankshaft. The
reluctor is a steel ring with 58 ’teeth’ and a space where two teeth are
’missing’. The teeth, and spaces between, each represent 3° of crankshaft
rotation. The two missing teeth provide a reference for angular position. As
the reluctor rotates adjacent to the sensor tip, a sinusoidal voltage waveform
is produced which can be interpreted by the ECM into crankshaft angular
position and velocity.
The signal from the CKP sensor is required by the ECM for the following
functions:



To determine fuel injection timing.
To enable the fuel pump relay circuit (after the priming period).
To produce an engine speed message for broadcast on the CAN bus
for use by other systems.
The two pins on the sensor are both outputs. To protect the integrity of the
CKP signal the cable incorporates a screen.
The cable screen earth path is via the ECM. Correct CKP sensor outputs are
dependent upon the air gap between
the tip of the CKP sensor and the passing teeth of the reluctor ring. The CKP
air gap is not adjustable in this application.
In the event of a CKP sensor signal failure any of the following symptoms may
be observed:



Engine cranks but fails to start.
Engine misfires.
Engine runs roughly or stalls.
15
Camshaft Position (CMP) sensor
The CMP sensor is located on top of the engine on the camshaft cover. This
sensor is a Hall effect sensor producing one pulse for every camshaft
revolution. The CMP sensor is only used on start up to synchronise the ECM
programme with the CKP signal. This is to identify number one cylinder for
correct injection timing. Once this has been achieved the input from the CMP
sensor is no longer used in any of the ECM strategies.
Electrical input to the CMP sensor is supplied via the main relay located in
engine compartment fuse box. One output is sensor earth, the other is the
signal output to the ECM.
In the event of a CMP sensor signal failure the engine will crank but will not
start.
Mass Air Flow/ Inlet Air Temperature (MAF/ IAT) sensor
The MAF/ IAT sensor is located on the engine intake air manifold, it combines
the two functions into one unit.
The MAF sensor works on the hot film principle. The MAF sensor has two
sensing elements contained within a film.
One element is at ambient temperature e.g. 25 °C (77 °F) while the other is
heated to 200 °C (392 °F) above this temperature e.g. 225 °C (437 °F). As air
passes through the MAF sensor it has a cooling effect on the film. The current
required to maintain the 200 °C (392 °F) differential provides a precise,
although non-linear, signal of the air drawn into the engine. The MAF sensor
output is an analogue voltage proportional to the mass of the incoming air.
The ECM utilises this data, together with information from the other sensors
and the fuelling maps, to determine the correct fuel quantity to be injected into
the cylinders. It is also used as a feedback signal for the EGR system.
The IAT sensor incorporates a Negative Temperature Coefficient (NTC)
thermistor in a voltage divider circuit. As the temperature of the intake air
increases, the resistance in the thermistor decreases. As the thermistor allows
more current to pass to earth, the voltage sensed at the ECM decreases. The
change in voltage is proportional to the temperature change of the intake air.
From the voltage output of the sensor, the ECM can correct the fuelling map
for intake air temperature. This correction is an important requirement
because hot air contains less oxygen than cold air for any given volume.
Inputs to the MAF sensor are a 12 volt supply from the engine compartment
fuse box and an earth path connection.
16
There are two outputs from the MAF sensor, these are in the form of a signal
and signal return connection to the ECM.
The IAT sensor utilises a 5 volt reference input from the ECM and shares the
earth path of the MAF. The output from the IAT is calculated within the ECM
by monitoring the changes in the reference voltage which supplies the IAT
voltage divider circuit. The MAF/ IAT sensor connector has gold plated
terminals.
If the MAF sensor fails the ECM implements a back up strategy, which is
based on engine speed. In the event of a MAF sensor signal failure any of the
following symptoms may be observed:






Difficult starting.
Engine stalls after starting.
Delayed engine response.
Emissions control inoperative.
Idle speed control inoperative.
Reduced engine performance.
Should the IAT sensor fail the ECM defaults to an assumed air temperature of
-5 °C (23 °F).
In the event of an IAT sensor signal failure any of the following symptoms may
be observed:


Over fuelling resulting in black smoke.
Idle speed control inoperative.
Mass Air Flow Meter
1. Sensor
2. Electrical Connector
17
Boost Pressure (BP) sensor
The BP sensor is located on the front side of the intake manifold and has a
three pin connector. It provides a voltage signal relative to intake manifold
pressure to the ECM. The BP sensor works on the piezo ceramic crystal
principal. Piezo ceramic crystals are pressure sensitive and, in the BP sensor,
oscillate at a rate dependent on air pressure.
The BP sensor produces a voltage between 0 and 5 volts proportional to the
pressure level of the air in the intake manifold. A reading of 0 volts indicates
low pressure and a reading of 5 volts indicates high pressure. The ECM uses
the signal from the BP sensor for the following functions:



To maintain manifold boost pressure.
To reduce exhaust smoke emissions while driving at high altitude.
Control of the EGR system.
ECM supplies the BP sensor with a 5 volt power supply. The output from the
BP sensor is measured at the ECM. The earth path is supplied via the ECM.
In the event of a BP sensor signal failure any of the following symptoms may
be observed:
 Altitude compensation inoperative (engine will produce black smoke).
 Active boost control inoperative.
The ECM assumes a default pressure of 0.9 bar (13 lbf/in 2 ).
Accelerator Pedal Position Sensor (APP)
The APP sensor is located on the pedal box in the driver’s footwell. The APP
sensor consists of two resistance tracks and two sliding contacts, effectively a
pair of potentiometers, connected to the accelerator pedal assembly. The use
of a pair of identical sensing elements ensures a position signal is still
provided even if one of the sensing elements develops a fault; this is required
18
because there is no mechanical linkage between the accelerator pedal and
the ECM.
As the accelerator pedal is depressed, the sliding contacts move along the
resistance tracks to change the output voltage of the sensor.
By monitoring the voltage outputs from the APP, the ECM is able to determine
the position, rate of change and direction of movement of the accelerator
pedal. It will also store the voltages which correspond with closed ’throttle’
and wide open ’throttle’ and will adapt to new ones in the event of component
wear or replacement.
The ECM uses the APP voltage to determine closed ’throttle’ position to
instigate idle speed control, and to enable the overrun fuel reduction strategy.
The APP sensor signal is also broadcast on the CAN bus, where it is used by
the EAT ECU to determine the correct point for gearshifts and kickdown.
The connector and sensor terminals are gold plated for corrosion resistance
and temperature stability, care must be exercised when probing the connector
and sensor terminals
The ECM supplies the APP sensor with a regulated 5 volts supply and an
earth path for the resistive tracks. The output signals vary according to the
position of the accelerator pedal. The APP sensor earth also acts as a screen
to protect the integrity of the signal.
If the APP sensor signal fails, the ECM increases the idle speed to 1,250
rev/min, and the engine speed will not increase when the accelerator is
depressed.
In the event of an APP sensor signal failure, the following symptoms may be
observed:



No accelerator response.
Failure of emission control.
Automatic gearbox kickdown inoperative.
Exhaust Gas Recirculation (EGR) modulator
The EGR modulator is located on the front of the engine at the side of the
starter motor. The EGR modulator is a solenoid operated valve which
regulates the vacuum source to the EGR valve, causing it to open or close.
The ECM utilises the EGR modulator to control the amount of exhaust gas
being recirculated in order to reduce exhaust emissions and combustion
noise. EGR is enabled when the engine is at normal operating temperature
and under cruising conditions.
The EGR modulator receives battery voltage from the main relay in the engine
compartment fusebox. The ECM completes the earth path to the solenoid
winding. The ECM controls the EGR valve operation using a PWM signal.
The duty cycle of the solenoid determines the amount of vacuum supplied to
the EGR valve and, therefore, the volume of exhaust gas allowed to enter the
cylinders.
In the event of an EGR modulator failure the EGR system will become
inoperative.
19
Brake switch
The brake switch is located on the pedal box assembly, it is a Hall effect
switch which detects the position of the brake pedal, and therefore when the
driver has applied the brakes. The ECM uses the signal from the brake switch
for the following:


To limit fuelling during braking.
To inhibit/ cancel cruise control if the brakes are applied.
The brake switch includes two separate circuits, one normally open and one
normally closed, connecting to earth. The two circuits are referred to as main
brake and brake test.
Brake switch outputs
In the event of a brake switch failure any of the following symptoms may be
observed:


Cruise control will be inactive.
Increased fuel consumption.
Switch
Brake light test
Brake not pressed
Open circuit
Brake pressed
Battery voltage
Main brake light
Ground
6-8 volts
Clutch switch
The clutch switch is a Hall effect device and is located on the pedal box
assembly. The clutch switch is activated when the clutch pedal is operated.
The ECM uses the signal from the clutch switch for the following functions:


To provide surge damping during gear changes.
To inhibit/ cancel cruise control if the clutch pedal is pressed.
20
Surge damping stops engine speed rising dramatically during gear changes.
Surge damping assists drivability in the following ways:



Smoother gear changes.
Greater exhaust gas emission control.
Improved fuel consumption.
The clutch switch receives a 12 volts reference voltage from the ECM. With
the clutch pedal in the rest position the switch is connected to earth. When the
clutch pedal is pressed the ECM receives a 12 volt signal.
In the event of a clutch pedal switch failure any of the following symptoms
may be observed:


Surge damping will be inactive
Cruise control will be inactive
Main relay
The main relay is located in the engine compartment fuse box. The relay
controls the voltage supplies to the main peripheral components of the system
under the control of the ECM. The ECM has a feed which allows it to become
active when it receives an input from the ignition switch position II (ignition
on). The ECM will then energise the main relay.
The main relay is a standard normally open 4 pin relay.
The main relay contact supplies battery voltage to the following components:






ECM.
MAF/ IAT sensor.
CMP sensor.
Fuel pressure regulator.
EGR modulator.
Glow plug ECU.
Voltage input to the relay winding and the contacts comes from the vehicle
battery. When the main relay is energised, the switching contact closes and
power is supplied to various components on the vehicle.
The earth path for the main relay winding is supplied by the ECM.
When the earth path is completed, the main relay energises.
In the event of a main relay failure any of the following symptoms may be
observed:


Engine will crank but not start.
The engine will stop if the relay fails.
21
Glow plug ECU and glow plugs
The glow plug ECU is located next to the ECM in the plenum. The ECM
controls all glow plug operations via the glow plug ECU. The glow plug
warning lamp is controlled by the ECM from information received from the
glow plug ECU.
The 4 glow plugs are located in the cylinder head on the inlet side. The glow
plugs form a vital part of the engine starting strategy. The glow plugs heat the
air inside the cylinder during cold starts to assist combustion. The use of glow
plugs helps to reduce the amount of extra fuel required on start up, the main
cause of black smoke. It also requires less injection advance, which reduces
engine noise, particularly when idling with a cold engine.
The main part of the glow plug is a tubular heating element that protrudes into
the combustion chamber of the engine.
The heating element contains a spiral filament encased in magnesium oxide
powder. At the tip of the tubular heating element is the heater coil. Behind the
heater coil, and connected in series, is a control coil. The control coil
regulates the heater coil to ensure that it does not overheat.
Pre-heat is the length of time the glow plugs operate prior to engine cranking.
The ECM controls the pre-heat time of the glow plugs based on battery
voltage and coolant temperature information.
Post-heat is the length of time the glow plugs operate after the engine starts.
The ECM controls the post-heat time based on ECT information. If the ECT
fails, the ECM will operate pre-heat and post-heat time strategies with default
values from its memory. The engine will be difficult to start.
The glow plug ECU is supplied with power directly from the vehicle battery, an
earth connection directly to the vehicle body from the glow plug ECU is used.
The glow plug ECU also receives a voltage signal from the main relay to
indicate ignition switch operation. Input information relating to engine
temperature and time base calculations comes from the ECM. The glow plug
ECU is able to process this information and then supply output control to the
glow plugs in the engine.
In the event of a glow plug failure any of the following symptoms may be
observed:

Difficult starting.
22

Excessive smoke emissions after engine start.
Pin no
1
2
3
4
5
6
7
8
9
10
11
12
Description
Battery supply
Glow plug cyl 3
Glow plug cyl4
Not used
Module earth
Not used
Not used
Glow plug cyl 2
Glow plug cyl 1
Glow plug operation control from ECM
Glow plug heater feedback to ECM
Switched power ignition position II
Input/output
Input
Output
Output
Output
Output
Output
Input
Output
Input
23
Sectioned injectors
a. injector closed (at rest)
b. injector open (injection)
1. fuel return
2. electrical connection
3. activation unit (solenoid valve)
Sectioned injectors
4. high pressure fuel supply
5. valve control chamber
6. valve ball
7. inlet port
8. outlet port
9. valve control piston
10. supply channel to nozzle
11. nozzle needle
24
Referring to the picture, the high-pressure connection (4) guides the fuel
through a channel (10) to the nozzle and also through the supply throttle (7) in
the control chamber (5).
The control chamber is connected to the fuel return line (1) by the outlet
throttle (8), which is opened by a solenoid valve. When the outlet throttle is
closed, hydraulic force on the valve piston (9) exceeds that on the pressure
stage of the injector needle (11). Consequently, the injector needle is pressed
into its seat and seals the high-pressure channel off from the engine
compartment. Fuel cannot enter the combustion chamber, although it is
constantly pressurized at the high-pressure connection.
When the injector activation unit is actuated (solenoid valve), the outlet throttle
is opened. This reduces the pressure in the control chamber, and therefore
the hydraulic force on the valve piston.
As soon as the hydraulic force drops below that on the pressure stage of the
injector needle, the injector needle opens, which allows the fuel to enter the
combustion chamber through the spray apertures.
This indirect activation of the injector needle via a hydraulic force increasing
system is used because the force required to open the injector needle using
the solenoid valve cannot be produced directly. The control quantity required
in addition to fuel quantity injected enters the fuel return line via the control
chamber throttle.
In addition to the control quantity, fuel is also lost at the throttle needle and
valve piston guide (leakage quantity).
The function of the injector can be sub-divided into four operating statuses
when the engine is running and the high-pressure pump is delivering fuel:
• Injector closed (under high pressure)
• Injector opens (start of injection)
• Injector fully open
• Injector closes (end of injection)
These operating statuses are applied according to the distribution of force
amongst the components of the injectors. If the engine is not running, the
nozzle spring closes the injector.
Injector closed (at rest)
When at rest, the solenoid valve is not activated and is therefore closed.
Because the outlet throttle is closed, the armature ball is pressed into the
lodgment at the drain throttle by the valve spring. The rail high pressure
accumulates in the valve control chamber. The same pressure is also exerted
in the chamber volume of the nozzle. The forces applied by the pressure to
the surfaces of the control piston and the force of the nozzle spring keeps the
injector needle closed against the opening force attacking its pressure stage.
Injector opens (start of injection)
The injector is at rest. The solenoid valve is activated by the starting current of
20 amps, which enables the solenoid valve to be opened quickly. The force of
the activated electromagnet exceeds that of the valve spring and the armature
opens the final throttle. After a maximum of 450 ms, the increased starting
25
current of 20 amps is reduced to a lower retaining current of 12 amps from the
electromagnet. This is possible because the air gap of the magnetic circuit is
now smaller.
Opening the drain throttle allows fuel to flow out of the valve control chamber
into the cavity above, and then to the fuel tank via the fuel return line. The
inlet port prevents complete compensation from taking place and the pressure
in the valve control chamber drops. As a consequence, the pressure in the
valve control chamber is lower than the pressure in the chamber volume of
the nozzle which still has the same level of pressure as the rail. The reduced
pressure in the valve control chamber leads to less pressure being exerted on
the control piston and to the injector needle being opened.
Injection commences.
The speed at which the injector needle opens is determined by the difference
in through put in the inlet and outlet throttle. After a stroke of approx. 200 mm,
the control piston reaches its upper limit point and stays there, supported by a
cushion of fuel. This cushion is the result of the stream of fuel created
between the inlet and outlet throttle. The injector nozzle is now completely
open and the fuel is injected into the combustion chamber at a pressure
approaching that of the pressure in the rail.
Injector closes (end of injection)
If the solenoid valve is no longer activated, then the armature is forced
downwards by the force of the valve spring. The ball then closes the outlet
port. To prevent excessive wear from the contact between the ball and the
valve’s lodgment, the armature consists of two parts. Although the armature
plate is guided downwards by a cam, it can also oscillate downwards by
means of a reset spring, there by preventing the armature and ball from being
subject to any downward forces. As in the rail, closing the outlet port causes
pressure to accumulate in the control compartment through the inlet of the
inlet port. This increased pressure exerts greater force on the surface at
the head end of the control piston. This force from the valve control chamber
and the spring force exceed the force from the chamber volume, the injector
needle closes. The speed at which the injector needle closes is determined by
the through put of the inlet port. Injection stops once the nozzle needle
reaches its lower limit point.
Fuel filter
The fuel filter is located adjacent to the battery box
The fuel filter cleans fuel from the fuel tank and helps prevent premature wear
to delicate components. Insufficient filtration can cause damage to pump
components, pressure valves and fuel injection nozzles. It does not feature
any electrical fuel heating and does not have a water separator.
To prevent clogging up the filter at low temperatures, there is a bimetal valve
in the return line.
This valve prevents heated fuel residue from mixing with cool fuel from the
tank.
26
Low pressure fuel sensor
The low pressure fuel sensor is used to detect the system pressure in the low
pressure fuel system from the in-line electric pump. The sensor is built into the
turret of the fuel filter, adjacent to the battery box.
This sensors information enables the EDC EMS to reduce the fuel injection
quantity at excessively low inlet pressures to the point where engine speed
and rail pressure are reduced accordingly.
The requisite inlet volume to the high-pressure pump is reduced. This makes
it possible for the inlet pressure to the high-pressure pump to rise to the
required level.
At an inlet pressure of less than 1.7 bar, high-pressure pump damage is
possible due to inadequate lubrication. To protect the high-pressure pump,
the EMS will shut down the engine if it receives a signal informing it of a lowpressure situation. The engine can be shut down if a differential pressure of
less than or equal to 0.5 bar develops between the inlet and the return lines
(pump protection).
Fuel heating and cooling
The bimetal valve (thermocouple) is situated on the outside of the fuel filter
housing, (for example, it is no longer directly situated on the fuel filter itself).
A fuel cooler is fitted next to the rear right hand wheel, the same location as
for the charcoal canister on petrol derivatives. The fuel returning from the
engine is at a very high temperature and must be cooled before it is returned
to the swirl pot. If the fuel is less than or equal to 6°C °C), 60% to 80% of
the fuel return flows directly to the line feeding the in-line electric fuel pump
and the fuel filter, the rest of the fuel returns to the fuel tank via the fuel cooler.
When the fuel is greater than or equal to 7°C °C), 100% of the fuel is
directed to the fuel cooler.
From the cooler, the fuel is returned to the swirl pot, via an in-tank duck bill
valve, where it is again picked up by the fuel pump.
Because diesel engines produce less vapour than petrol engines, venting is
carried out by a single centre vent.
27
Fuel system data can be seen in the table ’Fuel system technical data’
Fuel system technical data
Description
Data
System
Common Rail Direct Injection
Fuel Specification
Pressure Regulator Setting
En590 Diesel
350 kPa (3.5 Bar )
Fuel Tank Pump
Fuel Pump Output
Electric In Fuel Tank
250 kPa (2.5 Bar)
Fuel Injection Pump
Fuel Pump Drive
Bosch Cp1 Mech High Pressure
Pump
Chain Driven By Crankshaft
Pressure Control Valve Limit
Injector Make
22 Bar
Bosch
Nozzle Type
Position
Injector Operating Pressure
Pre - Injection
Main - Injection
DSLA 145P 868
Central
250 – 1350 Bar
60* Btdc
25* Btdc
General
The ECM controls the operation of the engine using information stored within
memory in the form of maps. The maps contain data which is used to
determine the most efficient fuelling for any given driving condition. The ECM
also has maps for the operation of sub systems such as EGR. The ECM is an
adaptive unit which ’learns’ the characteristics of the vehicle components.
This feature allows the ECM to compensate for any variations in components
fitted to the vehicle in production, and to adapt to changes which may occur in
service. The ability to compensate for ’wear and tear’ and environmental
changes during the life of the vehicle ensures that the ECM can comply with
the emission control legislation over extended periods. The ECM is
programmed with a ’strategy’, this controls the decisions about ’when’ to turn
specific functions on and off. The inputs to this decision making process are
supplied by sensors, mounted at various locations on the vehicle, which
supply information to the ECM. If a sensor fails to supply information, the
ECM will use the remaining sensors, and insert a default value for the missing
information. This is not always possible, in which case the vehicle will be
disabled. Where a default is used, this may result in reduced drivability, or an
increase in fuel consumption and exhaust emissions. The ECM is
programmed with vehicle specific information known as a ’calibration’, this is
the data required to calculate the ’outputs’. This information along with sensor
inputs and interfaced data determines actuator output signals.
28
The ECM facilitates strategies such as:






Smoke limitation.
Active surge damping.
Automatic gear change.
Fuel reduction.
Engine cooling.
Combustion noise limitation.
During idle and wide open ’throttle’ conditions the ECM uses mapped
information to respond to the input from the APP sensor. To implement the
optimum fuelling strategy for idle and wide open ’throttle’ the ECM requires
input information from the following:
 CKP sensor.
 APP sensor.
 ECT sensor.
 MAF/ IAT sensor.
 High pressure fuel sensor.

This information is then compared to mapped information within the ECM to
facilitate acceleration using the following actuators and controllers:





EGR modulator - closed for cleaner combustion.
Fuel pressure regulator - increase fuel pressure to injector rail.
Electronic fuel injectors - injection duration longer.
A/C compressor clutch relay - de-energised during wide-open ’throttle’
to reduce engine load.
EAT ECU - kick down (automatic gearbox models).
During cold start conditions the ECM uses ECT information to determine if
cold start strategy is required. During cold start conditions the ECM will inject
more fuel into the cylinders and will initiate glow plug timing strategy for
effective cold starting. Normal fuel strategy is used during hot starts.
Injection control
The purpose of the injection control is to deliver a precise quantity of finely
atomised fuel into the combustion chambers at the correct times in the engine
cycle.
To precisely control fuel injection quantity and timing, the following information
must be available to the ECM:

Crankshaft speed and position: This information enables the ECM to
determine the volume of air induced into the cylinders and the position
of the crankshaft for timing purposes.
29

Camshaft position: This information enables the ECM to determine the
relative positions of the crankshaft and camshaft for timing purposes.
 Injection timing map information: This information provides the basic
data which is used by the ECM when calculating the injection timing
and quantity.
 Engine coolant temperature: This information is used, in conjunction
with the CKP and the fuelling map, to set the injection quantity to the
correct value.
 Injector rail pressure: This information is used during fuelling
calculations to correct the electrical opening times (injector duty cycle)
to compensate for variations in fuel pressure.
 Mass air flow: This information is used by the ECM to calculate the
mass of air which has entered the cylinders, and hence the amount of
oxygen available for combustion of the fuel. It also allows the ECM to
monitor EGR flow when the system is active.
 Intake air temperature: This information is required by the ECM to
provide a correction factor for differing intake air temperatures. Cold air
contains more oxygen than hot air for any given volume, therefore the
fuelling must be adjusted to suit the prevailing conditions.
Accelerator pedal position: This information is vital to the operation of the
ECM and the vehicle. The ECM interprets the electrical signal from the APP
as ’throttle’ demand and controls the power output of the engine accordingly.
Pilot fuel injection
Pilot fuel injection helps to reduce engine clatter and vibration. The ECM
provides this feature by opening the electronic fuel injectors briefly before
injecting the main charge of fuel. This makes the flame front propagation
through the main charge less abrupt, giving reduced levels of diesel knock.
Smoke limitation
This requires high injection pressure to improve the atomisation of the fuel
injected into the cylinders. By maintaining high fuel pressures at low engine
speeds the ECM maximises the atomisation of the fuel for conditions where
turbulence in the combustion chamber is reduced. The strategy contained in
the ECM does not allow more fuel to be injected than there is oxygen
available in the cylinders.
Active surge damping
Active surge damping is implemented to prevent the engine surging when the
EAT ECU changes gear, or the clutch switch indicates that the clutch pedal is
depressed. The ECM will reduce fuelling to lower the engine torque output,
thereby preventing engine surge.
Air Conditioning (A/C)
The A/C system is dependent on the ECM for actuation of the compressor
clutch. While the engine is running, the ECM receives a compressor on/off
30
request on the CAN bus every 10 seconds, and each time that the A/C is
turned on or off. When the request is for the compressor to be turned on, the
ECM will engage the compressor clutch providing the following conditions
exist:






All engine sensors are functioning.
The engine is not under heavy load (i.e. accelerator pedal is not fully
down).
The coolant temperature is not more than 118 °C (244 °F).
Evaporator temperature not less than -7 °C (25 °F).
Engine speed over 500 rev/min.
A/C refrigerant pressure within the specifications required by the
trinary switch.

The ECM engages the compressor clutch by providing an earth path for the
A/C compressor clutch relay winding. The contacts in the relay close and
supply a 12 volt feed to engage the compressor clutch. When the compressor
clutch request has been granted a confirmation message is broadcast on the
CAN bus.
If any of the conditions necessary to engage the compressor clutch cease to
exist, the ECM will disengage the compressor. The ECM broadcasts a
confirmation that the A/C clutch has been disengaged on the CAN bus.
Cooling strategy
The ECM controls cooling fan operation for the engine, automatic gearbox
and A/C condenser. With the ECM controlling cooling fan operation, it can
adjust injection duration and timing to compensate for additional engine load
imposed by the alternator during cooling fan operation. The ECM can request
one of three fan speeds depending on coolant temperature, EAT ECU and
A/C requests. These fan speeds are:
 Low: 250 rev/min.
 Medium: 800 rev/min.
 High: 1750 rev/min.

Priority will be given to the highest fan speed request. When A/C is requested,
fan speed is set to low, unless the EAT ECU or ECT requires a higher fan
speed. If the cooling request circuit of the trinary switch is open the fan speed
is then set to medium. High speed fan operation will be selected by one of the
following conditions:


Engine temperature is greater than 119 °C (246 °F).
EAT ECU request for increased cooling.
The ECM achieves fan speeds by sending a 140 Hz PWM signal to a PWM
converter located within the fan relay module. The PWM converter is
connected to three relays, also located within the fan relay module, and
determines which relays to energise by the duty cycle of the pulse:
31



l13%: Relay one energised to give low fan speed.
40%: Relays one and two energised to give medium fan speed.
86%: Relays one, two and three energised to give high fan speed.
Electronic Automatic Transmission (EAT) ECU strategy
On automatic gearbox models, the EAT ECU implements an idle neutral
strategy, which is part of the fuel reduction strategy. Neutral is selected,
reducing engine load and fuel consumption, when all of the following
conditions are met:



ECM confirms engine at idle.
’D’ selected on gear selector lever.
Foot brake applied.
Should one of these conditions change, after neutral has been selected, ’D’
will be reselected automatically.
When the EAT ECU requests, via the CAN bus, a reduction in engine torque,
the ECM reduces engine torque by cutting back fuel delivery. This ensures
smooth gear changes throughout the engine speed and load ranges, and
reduces exhaust emissions.
Information sent from the ECM to the EAT ECU using the CAN bus is as
follows:
 Accelerator pedal position.
 Engine torque.
 Engine speed.
 Coolant temperature.
 Ignition key position.
 Virtual ’throttle’ angle.

Information sent from the EAT ECU to the ECM using the CAN bus is as
follows:





Torque reduction requests.
Gear lever position.
Current gear.
Gear change in progress.
Additional cooling request.
Immobilisation system
The ECM plays a major role in the immobilisation of the vehicle. The ECM
inhibits engine fuelling until the ECM receives a valid coded signal from the
immobilisation ECU. The coded signal from the immobilisation ECU comes in
the form of a rolling code. This code cannot be copied or bypassed in any
way.
32
When new, the immobilisation ECU is blank and is programmed with a
starting code known as a ’seed’. The seed is then used as a base point for the
rolling code when the immobilisation ECU is synchronised to the ECM during
manufacture.
Once synchronised, the ECM and immobilisation ECU are not
interchangeable and work as a matching pair.
When a new ECM is fitted to a vehicle during service, the new ECM must be
in a blank condition. The blank ECM must be re-synchronised to the
immobilisation ECU using TestBook.
When a new immobilisation ECU is fitted to a vehicle during service, the new
immobilisation ECU must be supplied with a seed that matches the vehicle.
This information is held by Rover. The rolling codes in the new immobilisation
ECU and the existing ECM must then be synchronised using TestBook.
The immobilisation ECU receives engine speed information from the ECM to
inhibit starter motor operation when the engine is running, to prevent damage
to the starter drive pinion and ring-gear. Engine speed information is
broadcast on the CAN bus by the ECM. The instrument pack converts and
broadcasts the engine speed signal on the K bus where it is received by the
immobilisation ECU.
Cruise control
The ECM incorporates a cruise control program which is activated and
deactivated by an input from the cruise control interface ECU.
During cruise control operation, the ECM controls vehicle speed by adjusting
fuel injection duration and timing. On automatic gearbox models, when the
accelerator pedal is released during cruise control the ECM outputs a
calculated ’throttle’ angle signal to the EAT ECU in place of the actual ’throttle’
angle signal derived from the APP sensor. The calculated ’throttle’ angle is
derived from fuel demand.
ECM connector details (C0603)
Pin no
1
2&3
4
5
6
7
8
9
Description
Battery voltage
Not used
Earth
Earth
Earth
Ignition voltage
Main relay supply
Main relay earth
Input/output
Input
Input
Input
Output
33
ECM connector details (C0604)
Pin no
1 to 8
9
10
11 to16
17
18 to 24
Description
Not used
Fuel pressure sensor supply
Fuel pressure sensor earth
Not used
Fuel pressure sensor signal
Not used
Input/output
Output
Input
34
ECM connector details (C0606)
Pin no
1
2
3
4
5
6
7 to 9
Description
MAP sensor supply
MAP sensor signal
MAP sensor earth
CMP signal
Not used
CKP signal
Not used
Input/output
Output
Input
10
11
12
13
14
15
16
17
18
19
20
21 to 27
28
29
30
31
EGR
Not used
Glow plug control
Not used
Boost pressure sensor supply
Boost pressure sensor signal
Boost pressure sensor earth
CMP earth
Not used
Speed signal screen earth
Fuel rail pressure sensor earth
Not used
ECT signal
IAT signal
Not used
CKP earth
Output
32
33
34
35
ECT earth
Fuel pressure sensor signal
Not used
Fuel rail pressure sensor
supply
36 & 37
38
39 & 40
41
42 to 49
Not used
Fuel pressure regulator
Not used
Oil pressure switch
Not used
50
51
52
Charge check alternator
Not used
Fault status glow plug relay
Input
Input
Output
Output
Input
Input
Input
Input
Output
Output
Input
Input
Input
35
ECM connector details (C0331)
Pin no
1
2&3
4
5&6
7
8
9
10
11
12
13
14
15 to 21
22
23
24
25
26
27
28
29
30 & 31
32
33
34 & 35
36
37
38 to 40
Description
Charge check alternator
Not used
Engine fan control
Not used
APP earth
APP signal
APP supply
Fuel pump
Oil pressure sensor
APP earth
APP signal
APP supply
Not used
Vehicle speed sensor
Clutch switch
Brake switch main circuit
Not used
Ignition voltage
Cruise control ECU
Brake switch test circuit
Compressor relay
Not used
Diagnostic interface
Immobilisation
Not used
CAN high
CAN low
Not used
Input/output
Output
Output
Input
Output
Output
Output
Input
Output
Input
Input
Input
Input
Input
Input
Output
Input/output
Input/output
Input/output
Input/output
ECM connector details (C0332)
Pin no
1
2
3
4
5
6
7
8
9
Description
Supply electronic fuel injector
Cylinders 2 & 4
Not used
Electronic fuel injector cylinder 2
Supply electronic fuel injector
Cylinders 1 & 3
Electronic fuel injector cylinder 1
Electronic fuel injector cylinder 4
Not used
Electronic fuel injector cylinder 3
Not used
Input/output
Input
Input
Input
Output
Output
Output
36
Component Location
37
EDC L-SERIES
1. Fuel injector with needle lift sensor
2. Brake pedal switch
3. Manifold absolute pressure (boost) sensor
4. Road speed sensor
5. Crankshaft position sensor
6. Mass air flow/intake air temperature sensor
7. Main relay
8. Cooling fan relay 1
9. Air conditioning compressor clutch relay
10. Engine control module
11. Fuel injection pump
12. Standard fuel injector (x 3)
13. Glow plug (x 4)
14. Engine coolant temperature sensor
15. Glow plug relay
16. Accelerator pedal position sensor
17. Glow plug warning lamp
18. Engine malfunction lamp
38
DESCRIPTION
General
The engine management system consists of an Engine Control Module (ECM)
that uses inputs from engine sensors to calculate the fuel quantity and
injection timing required for optimum combustion.
The calculated fuel quantity and injection timing are transmitted on a
Controller Area Network (CAN) bus to the fuel injection pump, which then
meters and distributes the fuel to the fuel injectors.
The CAN bus is a serial communications data bus, consisting of two wires
twisted together, that allows the high speed exchange of digital messages
between the two units.
The engine management system is a ’Drive by Wire’ system. The accelerator
pedal is not physically connected to the engine, but instead is connected to a
sensor, which provides the ECM with a signal proportional to accelerator
pedal position.
The engine management system interfaces with the alarm ECU for
immobilisation/ remobilisation of engine fuel control.
ECM
The ECM consists of an Integrated Circuit (IC) installed in an alloy casing.
Two electrical
Connectors provide the interface between the IC and the engine harness. The
ECM is installed in the engine compartment on the side of the battery carrier.
In addition to calculating the fuel injection
Quantity and timing, the ECM also controls the operation of the:• Glow plugs.
• Exhaust Gas Recirculation (EGR) system
• Air Conditioning (A/C) compressor (where fitted).
• Cooling fan(s).
The ECM incorporates short circuit protection and can store intermittent faults
on certain inputs.
TestBook can interrogate the ECM for these stored faults via the diagnostic
socket. If certain system inputs fail, the ECM implements a back-up facility to
enable the system to continue functioning, although at a reduced level of
performance.
As part of the security system’s immobilization function, a vehicle specific
security code is
programmed into the ECM and alarm ECU during production. The ECM
cannot function unless it is connected to an alarm ECU with the same code. In
service, replacement ECM are supplied uncoded and must be programmed
using TestBook to learn the vehicle security code from the alarm ECU.
ECM inputs and outputs are detailed in the following table:
39
ECM pin locations
40
41
Can-inputs
• Cam plate (pump) speed. Used by ECM for monitoring purposes.
• Pulse width of last injection. Time that fuel quantity solenoid valve was
energised during last injection. Used by ECM for monitoring purposes.
• Current pump temperature. Used in fuel quantity calculations
• Cylinder No. of last injection. Used by ECM for monitoring purposes.
• Pump status. Response to diagnostic request for stored fault messages.
• Result of self test. Results of test performed each time the pump ECU is
reset.
Can-outputs
• Begin of delivery referenced to engine TDC. Used by pump ECU to calculate
point at which fuel quantity solenoid valve is energised.
• Begin of delivery referenced to pump cam plate. Used by pump ECU to set
rate of discharge.
• Injection quantity. Used by pump ECU to determine duration that fuel
quantity solenoid valve is energised.
42
• Engine speed. Used by pump ECU for monitoring purposes.
• Multiplexed information. Defines engine management configuration.
Crankshaft Position (CKP) sensor
The speed and position of the engine is detected by the CKP sensor which is
bolted to, and projects through, the gearbox adaptor plate adjacent to the
flywheel.
The CKP is an inductive sensor consisting of a bracket mounted body
containing a coil and a permanent magnet which provides a magnetic field.
The sensor is situated such that an air gap exists between it and the flywheel.
Air gap distance is critical for correct operation.
The flywheel has four holes positioned equally around the crankshaft
circumference at 90 degree intervals. When the flywheel rotates, as a hole
passes the sensor it disturbs the magnetic field inducing a voltage pulse in the
coil. This pulse is transmitted to the engine control module.
Four pulses are transmitted to the ECM for each revolution of the flywheel. By
calculating the number of pulses that occur within a given time, the ECM can
determine the engine speed. The output from this sensor when used in
conjunction with that from the needle lift sensor is used for idle stabilization
and reference for injection timing.
Needle lift sensor
43
The ECM uses the input signals from the needle lift sensor to close the
injection timing loop. The needle lift sensor consists of a coil which surrounds
the shaft of an extended injection needle on No.1 fuel injector. The coil is fed
a DC supply from the ECM and produces a magnetic field. When the needle
is moved under the influence of fuel pressure, the magnetic field is disturbed
which induces an AC voltage in the coil. The induced voltage is registered in
the ECM as a reference point for the start of fuel injection.
Engine Coolant Temperature (ECT) sensor
The ECT sensor is a thermistor located in the top of the coolant outlet elbow.
The ECM constantly monitors the signal and uses the information to correct
the quantity of fuel injected and the injection timing especially during cold
starting. During starting, output from the sensor determines how long the
glow plugs are energised.
Manifold Absolute Pressure (MAP) sensor
The pressure of the intake air is monitored by a sensor located on the
bulkhead and connected, via a pressure tube, to the outlet side of the
turbocharger. The sensor is connected electrically to the ECM.
The ECM supplies a reference voltage to the sensor and translates the return
signal into a pressure value. When the intake air pressure changes, the
resistance across the sensor changes and affects the value of the return
signal.
The ECM uses the manifold absolute pressure, in conjunction with the intake
air temperature, to calculate the volume of oxygen in the air and adjust the
quantity of fuel being injected to achieve optimum fuelling of the engine.
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Vehicle speed sensor
The vehicle speed sensor is located on the top of the differential housing. The
vehicle speed sensor is driven by the final drive gear and produces an
electrical signal proportional to road speed. The output from the vehicle speed
sensor is used to drive the instrument pack speedometer in addition to
providing a signal to the ECM. The ECM uses this signal to provide active
surge damping and to adjust idle stabilisation.
Accelerator pedal position sensor
The accelerator pedal position sensor transmits accelerator pedal position
(i.e. driver demand) to the ECM. The sensor is installed on a bracket attached
to the driver’s side front inner wing and connected to the accelerator pedal by
a Bowden cable. A flying lead and connector from the base of the sensor
provides the interface with the vehicle wiring.
The accelerator pedal position sensor consists of an inductive position sensor
together with an idle switch. With the accelerator pedal released the idle
switch is open. When the accelerator pedal moves
enough to rotate the shaft of the sensor more than 9° the idle switch closes.
The idle switch signal is used by the ECM to implement idle speed control and
overrun fuel cut off, and to check the plausibility of the position sensor signal.
When the idle switch closes the ECM compares the signal voltage with a
pre-programmed value.
Accelerator pedal movement causes the voltage of the position sensor output
to vary. The ECM calculates the rate of change of the voltage in positive
(acceleration) or negative (deceleration) directions.
From this the ECM can determine the required engine speed, rate of
acceleration or rate of deceleration and apply acceleration enrichment,
deceleration fuel metering or over-run fuel cut-off as appropriate.
The ECM calculates a ’driver demanded fuel quantity’ from the position
sensor input. The ECM also calculates a ’maximum allowable fuel quantity’
based on mass air flow, engine speed, coolant temperature and strategies
such as smoke limitation, active surge damping and fuel reduction. If the
driver demanded fuel quantity is less than the maximum allowable fuel
quantity then the driver demanded fuel quantity is injected.
However, if the driver demanded fuel quantity is greater than the maximum
allowable fuel quantity, then the maximum allowable fuel quantity is injected
rather than that demanded by the driver.
Brake pedal switch
The brake pedal switch informs the ECM when the vehicle is braking and
allows it to implement active surge damping. The normally open switch closes
when the brake pedal is pressed and supplies a 12V feed to the ECM. The
ECM checks the plausibility of the brake switch input by comparing it with the
input from the accelerator pedal position sensor. If the inputs indicate the
brake pedal is pressed at the same time as the accelerator pedal, the ECM
interprets this as a fault.
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Glow plugs
The glow plugs assist starting by pre-heating the air in the cylinders. A glow
plug is installed in each cylinder, on the LH side of the cylinder head. The
glow plugs are connected in parallel to a feed from the glow plug relay and
earthed to the engine through the glow plug body. Operation of the glow
plug relay is controlled by the ECM.
When the starter switch is turned to position ’II’ the ECM energises the glow
plug relay and illuminates the glow plug warning lamp in the instrument pack.
The length of time the glow plug relay is energized depends on the engine
temperature determined by the ECM from the ECT sensor. Once the glow
plug relay has operated for the calculated time the ECM de-energises the
glow plug relay and extinguishes the glow plug warning lamp. If the engine is
cranked before the calculated time has elapsed, the ECM immediately deenergises the glow plug relay and extinguishes the glow plug warning lamp.
Intake Air Temperature/ Mass Air Flow (IAT/MAF) sensor
The IAT/MAF sensor supplies the ECM with separate signals for mass air flow
and intake air temperature. The sensor is installed in the intake duct, between
the air cleaner and the turbocharger.
The mass air flow is determined from the cooling effect of the intake air
flowing over a hot film resistor.
The temperature is determined from the output of a thermistor. The ECM
monitors the signals from the sensor and equates them to mass air flow and
temperature values.
Intake Air Temperature/ Mass Air Flow (IAT/MAF) sensor
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Fuel Injection Pump
1. Fuel inlet
2. Fuel outlet
3. Timing device plunger
4. Timing sensor
5. ECU
6. Axial piston
7. Distributor sleeve
8. Hydraulic head
9. Fuel quantity solenoid valve
10. Outlet to fuel injector
11. Non return valve
12. Timing device solenoid valve
13. Intermediate chamber
14. Cam plate
15. Timing ring
16. Toothed wheel
17. Supply pump
18. Drive pulley
19. Drive plate
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The fuel injection pump is an electronically controlled distributor pump
installed on the gearbox adaptor plate. The pump is driven at half engine
speed by a toothed drive belt from the rear end of the camshaft via a drive
pulley attached to the pump drive shaft.
In the pump housing the drive shaft is coupled to a four lobe cam plate and an
axial piston. Springs, acting on a flange on the axial piston, hold the axial
piston against the cam plate and the cam plate against four rollers mounted
on a timing ring. The timing ring is connected to a timing device consisting
of a plunger and a solenoid valve.
A toothed wheel and a vane type supply pump are installed on the drive shaft.
The toothed wheel is aligned with a timing sensor connected to the timing
ring, and has teeth at 3° intervals, except for 12° synchronisation gaps
opposite each lobe of the cam plate. Passages in the pump housing connect
the supply pump to the fuel inlet from the tank and to the intermediate
chamber containing the timing ring, cam plate and axial piston. A pressure
regulator valve is connected between the inlet and outlet sides of the supply
pump.
The end of the axial piston locates in a distributor sleeve attached to the
hydraulic head of the pump housing. Passages in the distributor sleeve and
the hydraulic head connect four equally spaced points around the axial piston
to individual outlets to the fuel injectors. A check valve is installed in each of
the fuel outlets. Further passages in the hydraulic head connect a pumping
chamber at the end of the axial piston to a fuel supply from the intermediate
chamber and to a fuel return port on the pump exterior. The fuel supply and
return flows are controlled by a fuel quantity solenoid valve.
An ECU is attached to the exterior of the pump housing and connected to the
engine harness.
Wires, inside protective sleeving attached to the outside of the pump housing,
connect the ECU to the timing device solenoid valve and the fuel quantity
solenoid valve. A conductive foil connects the ECU to the timing sensor. A
temperature sensor in the ECU senses the temperature of the pump
housing.
The input from the timing sensor is used by the pump ECU to determine the
position and speed of the cam plate. The cam plate position is used to
coordinate operation of the fuel quantity solenoid valve and for injection timing
and quantity control.
The cam plate speed is used in the cam plate position calculations, to
determine positions between the 3° intervals of the toothed wheel. To check
the plausibility of the timing sensor signal, the pump ECU compares cam plate
speed with the input from the engine speed sensor.
Warning lamps
There are two engine management related warning lamps in the instrument
pack: an amber glow plug warning lamp and an amber engine malfunction
lamp. The glow plug warning lamp illuminates while the glow plugs are
energised at the start of the ignition cycle. The engine malfunction lamp
illuminates if there is a fault with the ECM, fuel injection pump ECU or a
critical engine sensor.
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NOTE: An amber Malfunction Indicator Lamp (MIL) is installed in the
instrument pack for future use. Although the ECM performs a bulb
check on the MIL when the ignition is first switched on, the MIL is not
operational.
Air Intake System
The engine is supplied with pre-compressed air by a single stage
turbocharger.
Turbocharger
With the engine running, exhaust gases pass into the turbine side of the
turbocharger, causing the turbine to rotate and drive a compressor mounted in
the air intake ducting.
Intercooler
Intake air is drawn through the air cleaner to the turbocharger, where it is
compressed by the compressor. The compressed air is then fed into the
inlet manifold via an intercooler, which reduces the temperature and increases
the density of the compressed air.
Boost control
Boost control is achieved by a pneumatic actuator operating a mechanical flap
situated in the turbocharger which, when operated, allows exhaust gases to
bypass the turbine side of the turbocharger, so decreasing the rotational
speed of the turbine thereby reducing the pressure of the intake air.
The pneumatic actuator consists of a diaphragm connected to a mechanical
linkage which is opposed by an internal spring. Pressure from the compressor
side of the turbocharger is applied to the pneumatic actuator via a sensing
pipe.
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The pressure acting on the pneumatic actuator diaphragm builds up until it
exceeds the opposing force of the internal spring (approx. 1.2 Bar) causing
the mechanical linkage to move, thereby opening the flap on the turbocharger
and so reducing the boost pressure. As boost pressure is reduced the
mechanical linkage will move the other way closing the flap on the
turbocharger allowing the pressure to increase again. With the engine under
load the pneumatic actuator will be constantly opening and closing the flap on
the turbocharger.
OPERATION
General
Fuel is drawn from the tank by the fuel injection pump via a filter located in the
engine compartment.
The fuel injection pump pressurises and distributes precise quantities of fuel
to the fuel injectors and directs excess fuel back to the tank via a fuel return
line. Fuel quantities and injection timing are calculated by the ECM and
transmitted to the fuel injection pump on the CAN bus.
Fuel is injected directly into the cylinder head where it ignites. A swirl
chamber, machined into the piston crown, promotes efficient mixing of the fuel
with the already compressed air. The burning fuel expands rapidly in the
combustion chamber, creating extreme turbulence which further mixes the
burning fuel with the compressed air, providing complete combustion and
reducing emissions.
Engine starting
When the ignition switch is turned to position II a power feed is connected
from the ignition switch to the ECM. The ECM then initiates ’wake up’ routines
and energises the main relay and the glow plug from the alarm ECU, the ECM
also connects the fuel shut-off power supply to the pump ECU to enable
fuelling. If no mobilisation code is received from the alarm ECU, or the code is
invalid, the ECM withholds the fuel shut-off power supply to prevent fuelling.
After the glow plug pre-start heating time, the ECM extinguishes the glow plug
warning lamp to indicate the engine is ready to start. When the engine cranks,
the fuel injection pump distributes pressurised fuel to the injectors to start and
run the engine. After the post-start heating time, the ECM de-energises the
glow plug relay to stop heating the glow plugs.
Pre-start and post-start heating times for the glow plugs are determined by
the ECM from the engine coolant temperature.
Fuel injection pump
When the drive shaft of the fuel injection pump turns, fuel is drawn from the
tank by the supply pump and supplied to the intermediate chamber. The
incoming fuel flows through a chamber beneath the ECU to keep the ECU
cool. The supply to the intermediate chamber is regulated at 8 to 10 bar (120
to 145 lbf/in 2 ) by the pressure regulator valve.
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In the intermediate chamber, the fuel cools and lubricates the cam ring, cam
plate and axial piston.
A permanent flow of fuel passes from the intermediate chamber through the
passages in the hydraulic head to the tank return line. The flow cools the fuel
quantity solenoid valve and ensures there is a constant supply of fuel for the
pumping chamber.
Maximum return flow rate is 70 litres/hour (15.4 galls/hour).
As the cam plate and the axial piston turn with the drive shaft, the lobes of the
cam plate ride over the rollers on the timing ring and produce a reciprocating
movement of the axial piston. Due to the four lobes on the cam plate, the axial
piston moves through four inlet and compression stroke cycles per pump
revolution. On sequential compression strokes a passage in the rotating axial
piston connects the pumping chamber to the appropriate fuel injector outlet, in
engine firing sequence.
1. ECU
2. Fuel inlet
3. Fuel outlet
4. Fuel quantity solenoid valve
5. Axial piston
6. Non return valve
7. Outlet to fuel injector
8. Timing device plunger
9. Timing device solenoid valve
10. Pressure regulator valve
11. Supply pump
12. Timing ring
13. Cam plate
During each inlet stroke of the axial piston, the fuel quantity solenoid valve is
open to allow fuel from the intermediate chamber into the pumping chamber.
At the beginning of the compression stroke, the pump ECU closes the fuel
quantity solenoid valve. The axial piston then pressurises the fuel in the
pumping chamber and thus the line to the appropriate fuel
injector. When the pressure is sufficient to operate the fuel injector, the needle
valve in the fuel injector opens and an atomised spray of fuel is injected into
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the engine cylinder. When the required quantity of fuel has been injected, the
pump ECU opens the fuel quantity solenoid valve. This releases the pressure
in the pumping chamber and the needle valve of the fuel injector closes to
stop fuel injection.
During the compression stroke of the axial piston, the maximum pressure
produced in the pumping chamber is approximately 780 bar (11300 lbf/in 2 )at
a rated speed of 2100 rev/min. The rapid movement of the piston produces
shock waves in the fuel between the pumping chamber and the fuel injector.
The length of each fuel pipe, between the injection pump and the fuel injector,
is tuned to the frequency range of the shock waves, which increases the
pressure at the fuel injector to approximately 1200 bar (17400 lbf/in 2 ) at
rated speed.
Injection quantity
Fuel injection quantity is controlled by varying the length of time that the fuel
quantity solenoid valve is energised closed during the compression stroke of
the axial piston. The flow rate of the injected fuel is controlled by varying the
points on the cam lobe at which the fuel quantity solenoid valve closes and
opens, since the profile of the lobe is non linear.
Maximum injection duration at rated power is 17.5° of cam plate movement
(35° of crankshaft movement). Maximum possible injected quantity is 0.05 cm
3 /stroke.
Injection timing
The injection timing is adjusted by turning the timing ring. This alters the axial
piston movement relative to the pump drive shaft and thus the engine. The
control range of the timing ring is 15°(30° of crankshaft movement). The
position of the timing ring is controlled by the pump ECU via the timing device.
The plunger of the timing device is subjected to spring pressure and supply
pump inlet pressure on one end, and to servo pressure at the other end.
Servo pressure is derived from a restricted flow of supply pump outlet
pressure. The pump ECU controls the servo pressure, and thus the position of
the plunger and timing ring, using the timing device solenoid valve to regulate
a bleed of servo pressure back to the inlet side of the supply pump. The pump
ECU supplies the solenoid valve with a 50 Hz Pulse Width Modulated (PWM)
signal and varies the duty cycle of the signal to adjust the bleed of servo
pressure. The solenoid valve causes the characteristic buzzing from the fuel
injection pump while the ignition is switched on. Injection timing is fully
advanced with the solenoid valve de-energised.
The ECM receives an injection timing feedback signal from the needle lift
sensor in No. 1 fuel injector. If there is a significant difference between the
injection timing indicated by the feedback signal and the injection timing
requested on the CAN bus, the ECM assumes a fault exists and reduces the
quantity of fuel injected.
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Fuel shut-off
When the ignition is switched on, the ECM outputs a fuel shut-off power
supply to the pump ECU to enable control of the normally open fuel quantity
solenoid valve. When the ignition is switched off, or a serious engine problem
is detected, the ECM disconnects the fuel shut-off power supply. Without the
fuel shut-off power supply the fuel quantity solenoid valve is de-energised
open, which prevents pressure generation in the pumping chamber and
stops the supply of fuel to the injectors.
Exhaust Gas Recirculation (EGR) system
During certain running conditions the EGR system directs exhaust gases into
the intake manifold to be used in the combustion process. The principal effect
of this is to reduce combustion temperatures, which in turn reduces Oxides of
Nitrogen (NOx) emissions.
The EGR diaphragm valve is vacuum operated through a solenoid valve,
mounted on the engine bulkhead. When the ECM determines that exhaust
gas recirculation should take place, the solenoid valve is modulated and
vacuum, supplied by the brake servo vacuum pump, opens the EGR valve.
Exhaust gases are then fed through a pipe into the inlet manifold via an EGR
cooler.
The air flow meter, mounted in the air intake pipe, senses the volume of air
entering the engine. Using the principle that an increase in EGR decreases
the intake air flow, the ECM uses the input from the air flow meter to monitor
the amount of exhaust gases being recirculated. This feedback signal allows
the ECM to accurately control EGR operation.
Air Conditioning (A/C) compressor
When A/C is requested on the A/C switch, the ECM grants the request by
energising the A/C compressor clutch relay provided that:
• Driver demand is less than wide open throttle.
• The engine coolant temperature is within limits.
• There is no engine running problem.
• The engine is running below the maximum permitted continuous speed.
• The input from the A/C pressure switch indicates that refrigerant system
pressure is within the upper and lower limits.
• The input from the evaporator temperature sensor indicates that the
temperature of the air leaving the evaporator is above the minimum limit, i.e.
the evaporator is free from ice.
When it energises the A/C compressor clutch relay, the ECM also operates
the cooling and condenser fans at slow speed. When the input from the A/C
pressure switch indicates that the refrigerant system requires additional
cooling, the ECM switches the cooling and condenser fans to operate at high
speed.
While the A/C is on, if the throttle position, engine coolant temperature or
refrigerant system pressure exceed preset limits the ECM de-energises the
A/C compressor clutch relay to suspend A/C operation
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and reduce the load on the engine.
When the parameter returns within limits the ECM re-energises the A/C
compressor clutch relay to restore A/C.
A/C compressor clutch switching points
Input component
Accelerator pedal position
sensor
ECT sensor
off
Above
85*C
118*C (244*F)
on
Below
80*C
112*C (234*F)
A/C pressure sensor
Low limit
High limit
1.6 bar (23.2 psi)
29 bar (421 psi)
2.0 bar (29 psi)
23 bar (334 psi)
Cooling fans
The ECM controls the operation of the engine and condenser cooling fans by
switching relays. On non A/C models, the ECM switches a single relay in the
engine compartment fuse box to run the engine cooling fan at high speed. On
models with A/C, in addition to the relay in the engine compartment fuse box,
the ECM also operates two relays on the outside of the battery box to run the
engine cooling fan and the condenser cooling fan together, at either low or
high speed.
The ECM operates the cooling fan(s) in response to inputs from:
• The ECT sensor, for engine cooling.
• The A/C switch and A/C pressure sensor, for refrigerant system cooling.
On vehicles with A/C, if there is a conflict between requested cooling fan
speeds from the different inputs, the ECM adopts the highest requested
speed.
During the power down after the ignition is switched off, the ECM monitors the
engine coolant temperature for 4 minutes. Within that time, if the engine
coolant temperature exceeds 112 °C (234 °F) the ECM operates the cooling
fan(s) for 8 minutes or until the engine coolant temperature decreases below
106 °C (223 °F), whichever occurs first. Similarly, if the cooling fan(s) are
already running when the ignition is switched off, the ECM operates them for
8 minutes or until the engine coolant temperature decreases below 106 °C
(223 °F).
Engine/Condenser cooling fan switching points
Input componant
ECT sensor:
A/C models
Non A/C models
A/C switch
Fan speed on
off
Low
High
High
Low
104*C (219*F)
112*C (234*F)
104*C (219*F)
With switch
98*C (208*F)
106*C (223*F)
98*C (208*F)
With switch
19 bar (275 psi)
14 bar (203psi)
A/c pressure sensor High
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Diagnostics
The ECM has a built in self-diagnostic function. If a fault is detected, the ECM
stores a diagnostic trouble code in memory and illuminates the engine
malfunction lamp in the instrument pack. Where possible, the ECM also
implements a back-up facility to enable the system to continue functioning,
though at a reduced level of performance. If a serious fault is detected the
ECM disconnects the fuel shut-off supply to stop the engine or prevent it from
starting.
After a fault has been detected the engine malfunction lamp remains
illuminated until the ignition switch is turned off. If the fault is still present when
the ignition switch is turned back on, the engine malfunction lamp remains
illuminated after the bulb check.
The diagnostic socket, located on a bracket behind the centre console, allows
fault diagnosis via TestBook to be carried out without disturbing the system
electrical connections.
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