fuel LAND ROVER DEFENDER 1999 Repair Manual

ENGINE MANAGEMENT SYSTEM
3
DESCRIPTION AND OPERATION 1.Mass Air Flow (MAF) sensor.
2.Engine Coolant Temperature (ECT) sensor.
3.Glow plugs.
4.Manifold Absolute Pressure (MAP) / Inlet Air Temperature (IAT) sensor.
5.Fuel pump relay.
6.Engine Control Module (ECM).
7.Air Conditioning (A/C) and cooling fan relay.
8.Fuel Temperature (FT) sensor.
9.Crankshaft Speed and Position (CKP) sensor.
10.Electronic Unit Injectors (EUI).
11.Ambient Air Pressure (AAP) sensor.
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ENGINE MANAGEMENT SYSTEM
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DESCRIPTION AND OPERATION DESCRIPTION
General
An engine control module (ECM) controls the five cylinder direct injection diesel engine, and works on the drive by
wire principal. This means there is no throttle cable, the ECM controls the drivers needs via a signal from the
Throttle Position (TP) sensor on the throttle pedal.
The ECM is a full authoritative diesel specific microprocessor that also incorporates features for air conditioning. In
addition, the ECM supplies output control for the Exhaust Gas Recirculation (EGR) and turbocharger boost
pressure. The ECM has a self diagnostic function, which is able to provide backup strategies for most sensor
failures.
The ECM processes information from the following input sources:
Mass Air Flow (MAF) sensor.
Ambient Air Pressure (AAP) sensor.
Manifold Absolute Pressure (MAP) / Inlet Air Temperature (IAT) sensor.
Engine Coolant Temperature (ECT) sensor.
Crankshaft Speed and Position (CKP) sensor.
Throttle Position (TP) sensor.
Fuel Temperature (FT) sensor.
Air conditioning request.
Air conditioning fan request.
Brake pedal switch.
Clutch pedal switch.
The input from the sensors constantly updates the ECM with the current operating condition of the engine. Once
the ECM has compared current information with stored information within its memory, it can make any adjustment
it requires to the operation of the engine via the following:
Air conditioning clutch relay.
Air conditioning cooling fan relay.
Electronic vacuum regulator solenoid.
Fuel pump relay.
Glow plug warning lamp.
Glow plugs.
Fuel injectors.
Main relay.
Turbocharger wastegate modulator.
Temperature gauge.
The ECM interfaces with the following:
Serial communication link.
Instrument pack.
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ENGINE MANAGEMENT SYSTEM
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DESCRIPTION AND OPERATION SENSOR - MANIFOLD ABSOLUTE PRESSURE
(MAP) / INLET AIR TEMPERATURE (IAT)
The MAP/IAT sensors are combined in one unit located in the inlet manifold. It provides pressure and temperature
information about the air in the inlet manifold to the ECM. The ECM compares the voltage signal to stored values
and compensates fuel delivery as necessary. The ECM uses the signal from the MAP/IAT sensor for the following
functions:
To calculate the delivered fuel limits.
To calculate the air mass in the cylinder.
To calculate the air speed density.
To calculate the air temperature.
The MAP sensor works on the piezo crystal principal. Piezo crystals are pressure sensitive and will oscillate in
accordance to changes in air pressure. The MAP sensor produces a voltage between 0 and 5 volts proportional to
the pressure level of the air in the inlet manifold. A reading of 0 volts indicates a low pressure, a reading of 5 volts
a high pressure.
The IAT portion of the sensor works as a Negative Temperature Co-efficient (NTC) sensor. As air temperature
rises, the resistance in the sensor decreases. As temperature decreases the resistance in the sensor increases.
The ECM compares the voltage signal to stored values and compensates fuel delivery as necessary.
Inputs / Outputs
The MAP/IAT sensor (C0567-3) is provided a 5 volt supply by the ECM (C0158-8) on a pink/purple wire. The
MAP/IAT sensor provides the ECM with 2 outputs. The MAP sensor output (C0567-4) is connected to the ECM
(C0158-6) by a white/yellow wire. The IAT sensor output (C0567-2) is connected to the ECM (C0158-34) on a
green/black wire. The MAP/IAT sensor is earthed (C0567-1) via the ECM (C0158-17) on a pink/black wire.
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ENGINE MANAGEMENT SYSTEM
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DESCRIPTION AND OPERATION SENSOR - ENGINE COOLANT TEMPERATURE
(ECT)
The ECT sensor is located in the coolant outlet elbow on top of the engine. It provides the ECM with engine
coolant temperature information. The ECM uses this information for the following functions:
Fuelling calculations.
Temperature gauge.
To limit engine operation if coolant temperature is to high.
Cooling fan operation.
Glow plug operating time.
The ECT works as an NTC sensor. As temperature rises, the resistance in the sensor decreases, as temperature
decreases, the resistance in the sensor increases. The ECM compares the voltage signal to stored values and
compensates fuel delivery to ensure optimum driveability at all times.
Inputs / Outputs
The ECT sensor (C0169-2) is provided a feed by the ECM (C0158-7) on a pink/green wire. The sensor is provided
an earth path (C0169-1) via the ECM (C0158-18) on a pink/black wire.
The ECT can fail or supply an incorrect signal if one or more of the following occurs:
Sensor open circuit.
Short circuit to vehicle supply.
Short circuit to vehicle earth.
Incorrect mechanical fitting.
Signal fixed above 40°C (104°F) not detected.
Signal fixed below 40°C (104°F) not detected.
In the event of an ECT sensor failure, any of the following symptoms may be observed:
Difficult cold start.
Difficult hot start.
Driveability concerns.
Instrument pack warning lamp illuminated.
Temperature gauge reads excessively hot.
Temperature gauge reads excessively cold.
In the event of a component failure the ECM calculates coolant temperature from the fuel temperature signal. If
this occurs, the limit of engine operation if coolant temperature becomes too high becomes inoperative.
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18ENGINE MANAGEMENT SYSTEM
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DESCRIPTION AND OPERATION SENSOR - CRANKSHAFT SPEED AND
POSITION (CKP)
The CKP sensor is located in the transmission housing with its tip adjacent to the outer circumference of the
flywheel. The CKP sensor works on the variable reluctance principal, which sends a signal back to the ECM in the
form of an ac voltage.
The ECM uses the signal from the CKP sensor for the following functions.
To calculate engine speed.
To determine engine crank position.
To determine fuel injection timing.
The CKP sensor works as a Variable Reluctance Sensor (VRS). It uses an electromagnet and a target ring to
generate a signal. As the target ring passes the tip of the CKP sensor the magnetic field produced by the sensor is
cut and then re-instated. The ECM measures the signal as an ac voltage.
The outer circumference of the flywheel acts as the target ring for the sensor. The flywheel is divided into 36
segments, each of 10°. 31 segments have drilled holes and 5 segments are spaces. This equals 360°or one
engine revolution. The 5 spaces correspond to the TDC position of the 5 cylinders. This allows the ECM to control
fuel injection timing for each of the cylinders.
Inputs / Outputs
The two pins of the CKP sensor (C1068-1 & C1068-2) are both outputs. The ECM (C0158-13 & C0158-36)
processes the outputs of the sensor. To protect the integrity of the CKP sensor signal, an earth screen is used.
The ECM measures the outputs from the CKP sensor. The ECM (C0158-13) measures a positive signal on a
pink/black wire, and a negative signal (C0158-36) on a white/blue wire. The earth path for the sensor is via the
ECM (C0158-16).
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ENGINE MANAGEMENT SYSTEM
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DESCRIPTION AND OPERATION SENSOR - THROTTLE POSITION (TP)
FROM VIN 607225
Defender vehicles from VIN 607225 use three track thick film potentiometers. No idle speed sender switch is used
on this type of sensor because the ECM can compare the two or three sets of signals to implement idle speed
control and over-run fuel shut-off. The two potentiometers are known as track 1 and 2 potentiometers. The track 3
potentiometer on later models is used to improve the resolution of the pedal. The ECM provides a 5V supply and
receives a signal from each of the potentiometer tracks.
Td5 TP Sensor Signal Output
A = Track 1
B = Track 2
C = Track 3
D = Voltage
E = Pedal Angle (Degrees)
F = Not applicable for Defender
G = Wide open throttle stop tolerance band
With reference to the above graph, at idle (throttle released), track 2 returns a signal of 4.2V to the ECM and track
1 returns a signal of 0.8V. The ECM calculates the sum of these two figures which totals 5.0V.
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18ENGINE MANAGEMENT SYSTEM
18
DESCRIPTION AND OPERATION ELECTRONIC UNIT INJECTOR (EUI)
The EUI’s are located in the top of the engine inside the camshaft cover. There is one EUI per cylinder. They inject
finely atomised fuel directly into the combustion chamber. Each EUI has its own electrical connection, which is
linked to a common harness also located under the camshaft cover. Each of the EUI’s has its own 5 letter grading
code. This code is used so that greater EUI precision is achieved.
Using an injection timing map within its memory and information from the CKP sensor the ECM is able to
determine precise crankshaft angle. When the ECM determines the crankshaft speed and position it closes the
spill valve within the EUI. Fuel pressure rises inside the EUI to a predetermined limit of 1500 bar (22,000 lbf.in
2)on
pre EU3 models, and 1750 bar (25,500 lbf.in2) on EU3 models . At this limit the pintle lifts off its seat allowing the
fuel to inject into the combustion chamber. The ECM de-energises the spill valve to control the quantity of fuel
delivered. This causes a rapid pressure drop within the EUI which allows the EUI return spring to re-seat the
pintle, ending fuel delivery.
The electrical circuit that drives the EUI works in two stages depending on battery voltage. If battery voltage is
between 9 and 16 volts the EUI’s will provide normal engine performance. If however battery voltage falls to
between 6 and 9 volts on pre EU3 models, EUI operation is restricted to a limit of 2100 rev/min. On EU3 models,
EUI operation is restricted to idle. If the vehicle is fitted with a new ECM, the EUI grades for that specific vehicle
must be downloaded to the new ECM using TestBook. In the event of the engine failing to rev above 3000 rev/min
it is probable that the EUI grading has not been completed.
Input / Output
Input to the EUI takes the form of both mechanical and electrical signals. The mechanical input to the EUI is diesel
fuel via the fuel pump operating at approximately 4 to 5 bar (58 to 72 lbf.in
2). Each of the EUI’s is operated
mechanically by an overhead camshaft to enable injection pressures of up to 1500 bar (22,000 lbf.in2) on pre EU3
models, and 1750 bar (25,500 lbf.in2) on EU3 models, to be achieved. The ECM controls the EUI’s to ensure that
fuel delivery is precise and as intended.
The EUI’s earth paths are as follows:
EUI 1 (C0522-1) via the ECM (C0158-25) on a yellow wire.
EUI 2 (C0523-1) via the ECM (C0158-26) on a yellow/brown wire.
EUI 3 (C0524-1) via the ECM (C0158-27) on a yellow/blue wire.
EUI 4 (C0525-1) via the ECM (C0158-24) on a yellow/red wire.
EUI 5 (C0526-1) via the ECM (C0158-1) on a yellow/purple wire.
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ENGINE MANAGEMENT SYSTEM
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DESCRIPTION AND OPERATION The EUI can fail if one or more of the following occurs:
Open circuit.
Short circuit to voltage supply.
Short circuit to vehicle earth.
Wiring loom fault.
Connector water ingress.
Connector failure due to excess heat.
In the event of an EUI failure, any of the following symptoms may be observed:
Engine misfire.
Idle faults.
Reduced engine performance.
Reduced fuel economy.
Difficult cold start.
Difficult hot start.
Excess smoke.
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18ENGINE MANAGEMENT SYSTEM
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DESCRIPTION AND OPERATION SENSOR - FUEL TEMPERATURE (FT)
The FT sensor is located at the RH rear of the engine in the connector block, with the tip of the sensor inserted at
least 10mm into the fuel flow. This allows the sensor to respond correctly to changes in fuel density in relation to
fuel temperature.
The FT sensor works as an NTC sensor. As fuel temperature rises the resistance in the sensor decreases. As
temperature decreases the resistance in the sensor increases. The ECM is able to compare the voltage signal to
stored values and compensates fuel delivery as necessary for hot engine start.
The operating range of the sensor is -40 to 130°C (-40 to 266°F).
Input / Output
The ECM (C0158-19) provides the FT sensor (C0184-2) with a 5 volt supply signal on a yellow/white wire. The
sensor is earthed (C0184-1) via the ECM (C0158-5) on a pink/black wire.
The FT sensor can fail or supply an incorrect signal if one or more of the following occurs:
Sensor open circuit.
Short circuit to vehicle supply.
Short circuit to vehicle earth.
Sensor fitted incorrectly.
In the event of an FT sensor signal failure any of the following symptoms may be observed:
Difficult cold start.
Difficult hot start.
Driveability concern.
In the event of a component failure, the ECM reverts to a fixed value of 60°C stored in its memory.
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ENGINE MANAGEMENT SYSTEM
21
DESCRIPTION AND OPERATION RELAY - FUEL PUMP
The fuel pump relay is located in the engine compartment fuse box. It switches on the fuel pump to draw fuel from
the tank to the electronic unit injectors (EUI).
Input / Output
The fuel pump relay is a 4 pin normally open relay. The fuel pump relay (C0730-4) is provided with a feed by the
main relay (C0063-78) via header 291 on a brown/orange wire. An earth path is provided for the fuel pump relay
(C0730-6) via the ECM (C658-5) on a blue/purple wire. This energises the fuel pump relay and allows a feed to be
provided to the fuel pump. When the ECM interrupts the earth, the relay is de-energised and the fuel pump stops
operating.
The fuel pump relay can fail in one or more of the following ways:
Relay open circuit.
Short circuit to vehicle supply.
Short circuit to vehicle earth.
Broken relay return spring.
In the event of a fuel pump relay failure any of the following symptoms may be observed:
Engine will crank but not start.
If the engine is running, it will stop.
RELAY - MAIN
The main relay is located in the engine compartment fuse box and supplies battery voltage to the following:
The ECM.
The MAF sensor.
Fuel pump relay.
Input / Output
The main relay is a 4 pin normally open relay, which must be energised to provide a voltage to the ECM. The main
relay (C0063-86) is provided with an earth path via a transistor within the ECM (C0658-21) on a blue/red wire.
When the earth path is completed, the relay is energised and supplies the ECM (C0658-3, C0658-22 & C0658-27)
with a feed on brown/orange wires via header 291.
The main relay can fail in the following ways:
Relay open circuit.
Short circuit to vehicle supply.
Short circuit to vehicle earth.
Broken relay return spring.
In the event of a main relay failure any of the following symptoms may be observed:
Engine will crank but not start.
If the engine is running, it will stop.
For the ECM start up to take place the ignition feed when the switch is in position’II’must be greater than 6.0
volts.
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