1995 LAND ROVER DISCOVERY wheel

19FUEL SYSTEM
2
DESCRIPTION AND OPERATION Basic ignition timing
MEMS provides the optimum ignition timing for the
relevant engine speed and load. The speed and
position of the engine is detected by the crankshaft
sensor which is bolted to, and projects through the
engine adapter plate.
The sensor incorporates an armature which runs
adjacent to a reluctor insert in the flywheel, the insert
consisting of 34 poles spaced at 10°intervals, with
two missing poles 180°apart to identify the T.D.C.
positions.
The sensor 'reads' these poles to provide a constant
up-date of engine speed and crankshaft position to
the ECM
The load signal is provided by the manifold absolute
pressure sensor mounted inside the ECM casing
which detects manifold pressure via a hose connected
to the manifold chamber. The sensor converts
pressure variations into graduated electrical signals
which can be read by the ECMIgnition timing compensation
Coolant temperature sensor
When the ECM receives a low engine temperature
signal from the coolant sensor, it provides optimum
driveability and emissions by advancing or retarding
the ignition timing.
Knock sensor
The knock sensor is a capacitive device mounted in
the cylinder block between nos. 2 and 3 cylinders
below the inlet manifold. The sensor monitors noise
and vibration in the engine and passes this
information to the ECM which is able to identify the
characteristics of the knocking and make the
necessary corrections to the ignition timing of
individual cylinders.
Idle speed control
When the throttle pedal is released and the engine is
at idle, the ECM uses the fast response of ignition
timing to assist idle speed control.
When loads are placed on, or removed from the
engine the ECM senses the change in engine speed
and in conjuction with the opening of the throttle disc
by the stepper motor, advances or retards the ignition
timing to maintain the specified idle speed. When load
is removed from the engine and the stepper motor
returns to it's original position, the ignition timing
returns to the idle setting.
NOTE: Due to the sensitivity of this system
the ignition timing will be constantly
changing at idle speed.

19FUEL SYSTEM
8
DESCRIPTION AND OPERATION MEMS COMPONENTS & LOCATION ON ENGINE
Components Location
1 Fuel pressure regulator Engine rear...........................................
2 Intake air temperature sensor Inlet manifold.................................
3 Crankshaft sensor Under starter motor on flywheel housing...................................................
4 Twin ignition coils Engine rear....................................................
5 Oxygen sensor Exhaust manifold........................................................
6 Coolant temperature sensor Coolant chamber....................................
7 Injectors
8 Stepper motor
9 Throttle potentiometer
10 Fuel temperature sensor Fuel rail.........................................
11 Knock sensor Engine block..........................................................

CRUISE CONTROL
1
DESCRIPTION AND OPERATION CRUISE CONTROL COMPONENT LOCATIONS -
Tdi AUTO EDC
COMPONENT LOCATION
1. Cruise control unit Under LH dash...................................................
2. Engagement (on/off) switch Dash panel....................................
3. Cruise control switch Steering wheel...............................................
4. Rotary coupler Steering wheel.........................................................
5. Vacuum pump Box section under jack.........................................................
6. Brake/vent switch Brake pedal....................................................
7. Vehicle speed sensor Transfer box behind transmission brake..............................................
8. Neutral lock-out relay Behind RH lower 'A' post trim casing..............................................
9. Actuator RH engine compartment...................................................................

19FUEL SYSTEM
2
DESCRIPTION AND OPERATION CRUISE CONTROL SYSTEM - V8i/Tdi AUTO EDC
Description
The cruise control system consists of
electro-mechanical devices, and comprises of the
following components.
ELECTRONIC CONTROL UNIT (ECU)
The microprocessor based ECU evaluates the signals
provided by the driver controls, brake pedal switch,
clutch pedal switch on manual models, and the
vehicle speed sensor. The ECU activates the vacuum
pump as required. The ECU also has a memory
function for set speed storage.
Driver operated switches
The main cruise control switch is located in the
auxiliary switch panel and activates the cruise control
system. The steering wheel switches provide
'set/accelerate' and 'resume/decelerate' features.
These switches provide the interface between driver
and cruise control system.
Brake pedal switch
The brake pedal switch is located under the lower
dash attached to the brake pedal mounting bracket.
The switch provides for fast disengagement of the
cruise control system and rapid return of the throttle
levers to the idle position when the brake pedal is
applied.
Clutch pedal switch
The clutch pedal switch is located under the lower
dash attached to the clutch pedal mounting bracket.
The switch provides for fast disengagement of the
cruise control system and rapid return of the throttle
levers to the idle position when the clutch pedal is
applied.Vehicle speed sensor
The vehicle speed sensor is located on the side of the
transfer box adjacent to park brake. The sensor
provides road speed data to the ECU. The cruise
control system cannot be engaged until the road
speed exceeds 45 km/h, (28 mph) the system will
automatically disengage at a road speed of 42 km/h
(26 mph).
Vacuum pump
The vacuum pump is energised when the main cruise
control switch is operated, and is actuated by the
steering wheel and brake pedal switches. The pump
provides a vacuum source to the cruise control
actuator. A control valve in the pump provides for
steady increase of road speed or purge of the system
when the brake pedal is applied.
Actuator
The actuator provides the servo mechanism link
between the cruise control system and throttle linkage
and is operated by vacuum from the vacuum pump.
Neutral lockout relay - automatic vehicles
The relay module is located in the right hand side
footwell, accessible by removing the trim casing.
The function of the relay module is to disengage the
cruise control system if neutral, or park, is selected in
the main gearbox, when the system is engaged.
Engine speed trip ECU - Manual vehicles
This unit is located in the right hand side footwell,
accessible by removing the trim casing.
The function of the unit is to disengage cruise control
if engine speed exceeds 5000 rev/min.

19FUEL SYSTEM
2
REPAIR ENGAGEMENT (ON/OFF) SWITCH
Service repair no - 19.75.30
Switch Replacement
Remove
1.Disconnect battery negative lead.
2.Carefully release auxiliary switch panel from
fascia.
3.Disconnect multiplug from switch.
4.Depress retaining lugs on switch, remove switch
from panel.
Bulb replacement
5.Position switch to facilitate removal of bulb.
6.Rotate bulb holder 90°and withdraw it from
switch.CRUISE CONTROL SWITCH
Service repair no - 19.75.36
Remove
1.Disconnect battery negative lead.
2. Models fitted with airbags:Remove driver's
airbag module.
See SUPPLEMENTARY
RESTRAINT SYSTEM, Repair, Driver's
Airbag Module
3. Models without airbags:Turn steering wheel
through 90°. Remove 2 Torx screws securing
pad to steering wheel and remove steering
wheel pad.
4.Disconnect cruise control switch multiplug from
main harness.

CRUISE CONTROL
3
REPAIR
5.Disconnect 2 Lucars from horn contacts.
6.Remove 2 screws securing cruise control switch
to steering wheel.
7.Remove 3 bolts securing mounting bracket to
steering wheel and remove mounting bracket.
8.Remove cruise control switch from steering
wheel.
Refit
9.Reverse removal procedure. Ensuring wiring
harness is routed correctly.
10. Models fitted with airbags:Refit driver's airbag
module and follow all safety precautions.
See
SUPPLEMENTARY RESTRAINT SYSTEM,
Repair, Driver's Airbag Module
ROTARY COUPLER
Service repair no - 19.75.54
The rotary coupler is located behind the steering
wheel. Access is gained by removing the steering
wheel and steering column shroud.
NOTE: On vehicles fitted with airbags.See
SUPPLEMENTARY RESTRAINT SYSTEM,
Repair, Rotary Coupler
Remove
1.Disconnect battery negative lead.
2.Remove steering wheel.
See STEERING,
Repair, Steering Wheel
3.Release 2 turnbuckles securing lower dash
closing panel and lower.
4.Remove 3 screws securing lower half of shroud
to steering column.
5.Disconnect rotary coupler multiplug from
steering column harness.

19FUEL SYSTEM
4
REPAIR
NOTE: If rotary coupler is to be re-used a
piece of adhesive tape should be placed
around the moulding in position A to
prevent rotation. Failure to do this may result in
damage to the wires inside the coupler.
6.Release clips securing rotary coupler to column
stalk assembly.
7.Remove rotary coupler from column stalk
assembly.
CAUTION: Ensure front wheels are in the
straight ahead position before removal
and refitting. Store in a plastic bag. DO
NOT rotate mechanism whilst removed.
Refit
8.Reverse removal procedure. Ensuring that the
column harnesses are not trapped by the
column shroud.
NOTE: If original rotary coupler is to be
fitted and there is evidence of tampering, it
is imperative that the coupler is
centralised.
See SUPPLEMENTARY RESTRAINT
SYSTEM, Repair, Rotary Coupler
NOTE: If a new rotary coupler is to be
fitted and the sealing tape is broken it
MUST NOT be used. Ensure rotary coupler
lugs are correctly engaged in the rear of the
steering wheel.ACTUATOR - V8i
Service repair no - 19.75.12
NOTE: The actuator is non serviceable, fit
a new unit if failure or damage occurs.
Remove
1.Disconnect battery negative lead.
2.Disconnect vacuum hose from actuator.
3.Remove nut securing actuator to throttle bracket.
4.Remove actuator, and manoeuvre actuator
operating link off throttle lever.
5.Withdraw actuator.
Refit
6.Inspect rubber diaphragm. Fit a new actuator
assembly if diaphragm is damaged.
7.Reverse removal procedure. Fitting the hook
uppermost.

19FUEL SYSTEM
6
REPAIR VACUUM PUMP - TDI
Service repair no - 19.75.06
NOTE: The vacuum pump is non
serviceable, fit a new unit if failure or
damage occurs.
Remove
1.Release turnbuckle securing wheel chock and
remove.
2.Release strap securing jack and remove.
3.Release 3 pump mounting rubbers from vehicle
body.
4.Manoeuvre pump out of box section.
5.Release multiplug cover and disconnect
multiplug from pump.
6.Disconnect vacuum hose from pump.
7.Remove pump.
Refit
8.Reverse removal procedure. Ensure all hose
and electrical connections are secure.