1995 LAND ROVER DISCOVERY sensor

19FUEL SYSTEM
6
DESCRIPTION AND OPERATION DESCRIPTION ELECTRONIC DIESEL CONTROL
The Electronic Diesel Control (EDC) 'drive by wire'
system derives its from the replacement of
conventional mechanical controls by electronic
components.
The EDC system supplies the exact amount of fuel to
the engine according to the prevailing engine
operating conditions. To monitor these conditions,
sensors are fitted to the engine to measure engine
parameters. Data from the sensors is received by the
Engine Control Module (ECM) which determines the
exact amount of fuel, injection timing and Exhaust
Gas Recirculation (EGR) required for any running
condition.
Safety and emergency features are built into the
system which protect the engine against overspeed
and overheating damage. In the event of component
failure the system is designed to compensate and
allow emergency start and limp home facilities to
operate. The ECM does this by substituting a default
value for the failed component which may result in a
noticeable loss in power but keeps the engine
running.FUEL SYSTEM COMPONENT LOCATION EDC
1. Vehicle speed sensor
2. No. 4 injector sensor
3. Coolant temperature sensor
4. Boost pressure sensor
5. Electro-pneumatic modulator
6. Airflow sensor
7. Engine speed sensor
8. Brake/clutch switches
9. Injector pump
10. Throttle position sensor
11. Engine control module

19FUEL SYSTEM
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DESCRIPTION AND OPERATION FUEL SYSTEM LAYOUT EDC
1. Fuel injection pump
2. Fuel temperature sensor
3. Air temperature sensor
4. Water temperature sensor
5. No. 4 injector sensor
6. Air flow sensor
7. Engine speed sensor
8. Boost pressure sensor
9. Vehicle speed sensor
10. Clutch switch
11. Brake switch
12. Throttle position sensor
13. Electro-pneumatic modulator
14. Exhaust gas recirculation (EGR) valve
15. Engine control module (ECM)
16. Diagnostic indicator
A. To turbo
B. To air box.
C. To 'T' piece on brake servo hose position
D. Solenoid operated valve energization timing device.
E. Fuel cut off
F. Actuator current
G. Control collar

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DESCRIPTION AND OPERATION OPERATION EDC
Under start up conditions, signals from the crank
speed and water temperature sensors are relayed to
the ECM to control starting fuel quantity and injection
timing. Once the engine has started the ECM initiates
a 'closed loop' monitoring system for fuel quantity,
injector timing and EGR relative to the appropriate
engine operating conditions.
As driver demand increases, signals from the throttle
position sensor are received by the ECM together with
crank speed and position pulses. The ECM signals
the injection pump to adjust fuel quantity and timing
relative to driver demand.
As engine coolant, fuel and air temperature changes
the ECM will correct fuel delivery and injection timing
for more efficient and accurate running. The ECM will
also make corrections for atmospheric pressure on
injection timing and EGR.
Electronic Control Unit (ECM)
The EDC system is controlled by the ECM located in
the drivers footwell on the 'A' post beneath the fascia.
The unit consists of a microprocessor with integrated
circuits and components and is connected to the main
harness by a 55 pin plug.
Inputs to the ECM from engine sensors control start of
injection, injected fuel quantity, fuel cut-off and EGR.
The ECM will also make corrections for engine
coolant, fuel and air temperature and atmospheric
pressure.Injection pump
The injection pump incorporates actuator controlled
injected fuel quantity and solenoid operated timing
which operate in response to ECM signals against
driver demand, engine speed, temperature and boost
pressure.
A fuel cut-off facility and fuel temperature sensor is
incorporated in the pump.
Injection timing sensor
An inductive sensor in No 4 injector body monitors
needle movement. This forms part of a 'closed loop'
system to control start of injection.
The system measures timing, relating the needle
movement signal to crank position (determined by
flywheel pulses from the engine speed sensor).
Air flow sensor
The Air Flow Sensor is mounted on a bracket
attached to the wheel arch valance, and connected by
hose to the air cleaner and turbo charger inlet.
The unit consists of a flap valve airflow sensor which
measures the fresh air flow into the engine. The
sensor informs the ECM and, provided that the other
conditions are met, will implement EGR.
Engine speed sensor
The engine speed sensor is an active inductive sensor
mounted on the flywheel housing. Pulses from the
sensor activated by radial slots in the flywheel give
engine speed and position information to the ECM.

19FUEL SYSTEM
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DESCRIPTION AND OPERATION Vehicle speed sensor
The vehicle speed sensor is located on the transfer
box behind the transmission brake. The unit has a
multirole as the vehicle electronic speedometer
sensor and as a sensor for 'surge damping', (a
function which smooths out engine response to sharp
accelerator movement and reduces vehicle 'bucking').
The sensor is an additional input for engine overheat
protection.
Brake and clutch switches
The brake and clutch switches are located on the
pedal box and serve as safety features to the system.
They return information to the ECM which limits
maximum fuel quantity under braking.
Throttle position sensor
The accelerator pedal is connected directly to a
sensor mounted in the pedal box. Driver demand is
relayed back to the ECM to increase or decrease
injected fuel quantity.
Incorporated in the sensor is a backup idle switch
which the system will default to in the event of sensor
failure.
Boost pressure sensor
The boost pressure sensor is mounted on the
bulkhead. It relays boost pressure information to the
ECM which compensates fuel quantity to reduce
smoke during acceleration.
Electro-pneumatic modulator
The electro-pneumatic modulator is located on the
inner wing just forward of the air cleaner. It regulates
vacuum signals from the source to the EGR valve.
The ECM controls the modulator to open the EGR
valve according to required airflow.Exhaust gas recirculation valve
The EGR valve is located on the engine exhaust
manifold and is controlled by vacuum from the
electro-pneumatic modulator.
Once open the EGR valve directs a quantity of
exhaust gas back into the inlet manifold to be burnt
inside the engine. This reduces NOx (Oxides of
nitrogen) emissions of the engine.
Temperature sensors
Water, Fuel and Air temperature sensors monitor
engine conditions and relay their information back to
the ECM which makes adjustments to injected fuel
quantity, injection timing, EGR and corrections to
measured boost pressure and airflow.

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ADJUSTMENT THROTTLE CABLE
Adjust
1.Loosen throttle cable adjustment ferrule.
2.Hold throttle lever in fully closed position.
3.Adjust outer cable, by rotating ferrule, to give
1.57 mm (0.062 in) of free play in the inner
cable.
4.Check that throttle opens fully when the throttle
is depressed.EGR THROTTLE POSITION SENSOR
Check
1.Run engine until normal operating temperature is
reached.
2.Switch off engine and disconnect sensor
multiplug.
3.Connect an Ohmmeter across pins 1 and 3 of
multiplug. Ohmmeter should read between 1K
and 1.05K ohms.
4.Connect an Ohmmeter across pins 1 and 2 of
multiplug. Ohmmeter should read between 850
and 900 ohms.
5.If the readings are correct, EGR throttle position
sensor is Ok - reconnect multiplug.
6.Loosen 2 Torx screws securing sensor.
7.Rotate sensor to achieve correct Ohmmeter
readings, then tighten Torx screws.
8.Re-check Ohmmeter readings, then reconnect
multiplug.

19FUEL SYSTEM
10
REPAIR EGR THROTTLE POSITION SENSOR
Service repair no - 19.30.14
Remove
1.Remove 2 screws securing sensor mounting
plate to injection pump.
2.Disconnect sensor multiplug from harness.
3.Remove sensor assembly.
Refit
4.Position sensor assembly on injection pump and
fit and tighten screws.
5.Connect multiplug.
6.Adjust sensor.
See Adjustment, EGR Throttle
Position Sensor
INJECTORS
Service repair no - 19.60.10
Remove
1.Remove oil filler cap and remove sound
deadening pad from top of engine.
2.Remove high pressure pipe from relevant
injector and injection pump.
3.Disconnect spill return hose(s) from injector.
4.Plug pipes and injector connections to prevent
the ingress of dirt and foreign matter.
5.Remove nut securing injector clamp plate to
cylinder head.
6.Remove injector.
Refit
7.Reverse removal procedure. Renew copper
washer on injector. Tighten injector clamp plate
nut to
25 Nm.

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REPAIR BOOST PRESSURE SENSOR
Service repair no - 18.30.63
Remove
1.Disconnect battery negative lead.
2.Disconnect sensor multi-plug.
3.Disconnect pressure tube union.
4.Retrieve and discard union copper washers.
5.Place pressure tube aside.
6.Remove sensor to mounting bracket bolts.
7.Remove sensor.
Refit
8.Renew all copper washers.
9.Reverse removal procedure.
INJECTION TIMING SENSOR
Service repair no - 18.30.64
Remove
1.Disconnect battery negative lead.
2.Disconnect sensor multi-plug.
3.Disconnect spill return pipe to injector.
4.Disconnect injector union.
5.Remove copper washers.
6.Remove injector clamp fixing.
7.Remove clamp.
8.Remove injector.
9.Remove injector copper washers.
Refit
10.Renew all copper washers.
11.Reverse removal procedure.
12.Check for leaks when running.

19FUEL SYSTEM
16
REPAIR ENGINE SPEED SENSOR
Service repair no - 18.30.65
Remove
1.Disconnect battery negative lead.
2.Disconnect sensor multi-plug.
3.Place vehicle on ramp and apply handbrake.
4.Raise ramp.
5.Remove sensor retaining nut.
6.Remove sensor from housing.
7.Clean housing mating faces.
Refit
8.Reverse removal procedure.