1995 LAND ROVER DISCOVERY air condition

19FUEL SYSTEM
6
REPAIR ENGINE COOLANT TEMPERATURE SENSOR
Service repair no - 19.22.18
Remove
1.Position drain tray to collect coolant spillage.
2.Disconnect multiplug from coolant sensor.
3.Remove sensor from thermostat housing.
4.Remove and discard copper washer.
Refit
5.Fit a new copper washer.
6.Fit sensor and tigten securely.
7.Top-up cooling system.
8.Run engine, check for water leaks around
sensor.DEPRESSURISING FUEL SYSTEM
WARNING: Under normal operating
conditions the Multiport fuel injection
system is pressurised by a high pressure
fuel pump, operating at up to 2.3 to 2.5 bar When
engine is stationary pressure is maintained within
system. To prevent pressurised fuel escaping and
to avoid personal injury it is necessary to
depressurise multiport fuel injection system
before any service operations are carried out.
If vehicle has not been run there will be a small
amount of residual pressure in fuel line. The
depressurising procedure must still be carried out
before disconnecting any component within the
fuel system.
The spilling of fuel is unavoidable during this
operation. Ensure that all necessary precautions
are taken to prevent fire and explosion.
1.Remove fuel pump relay module.
See
Multiport Fuel Injection Relays
2.Start and run engine.
3.When sufficient fuel has been used to cause fuel
line pressure to drop, injectors will become
inoperative, resulting in engine stall. Switch off
ignition.
4.Disconnect battery negative lead.
NOTE: Fuel at low pressure will remain in
system. To remove low pressure fuel,
place absorbent cloth around fuel feed
hose at fuel rail.
5.Disconnect either:
a) Nut and olive at fuel rail
OR
b) Hose at inlet end of fuel filter.
Refit
6.Refit fuel feed hose.
7.Refit fuel pump relay module, reconnect battery.
8.Crank engine (engine will fire in approximately 6
to 8 seconds).

19FUEL SYSTEM
4
DESCRIPTION AND OPERATION Throttle position sensor (TP Sensor)
The throttle position sensor is mounted on the plenum
chamber and connected directly to the throttle shaft.
The sensor is a variable resistor, the signal from
which (0 - 5V) informs the ECM of the actual position
of the throttle disc. As there is no default strategy,
failure of the sensor will result in poor idle and lack of
throttle response. If failure occurs in the closed
position the engine will only reach 1750 rev/min when
the ECM will initiate overrun fuel cut off. The fault is
indicated by illumination of the malfunction indicator
light (MIL) on North American specification vehicles.
Engine coolant temperature sensor (ECT Sensor)
This sensor consists of a temperature dependant
resistive metal strip. The resistance of the strip varies
considerably with coolant temperature, i.e. from 28K
ohms at - 30°C to 90 ohms at 130°C, and 300 Ohms
at 85°C. The ECT Sensor signal is vital to engine
running, as the correct fuelling is dependant upon
engine temperature i.e. richer mixture at low
temperatures. If the sensor is disconnected or failure
occurs a default value will be supplied to the system.
The initial default value selected will be based on the
value of the air intake temperature. This will increase
to a nominal warmed up value over an individual time,
programmed for each default value. The fault may not
be evident to the driver, there may be a hot restart
problem. The fault is indicated by illumination of the
malfunction indicator light (MIL) on North American
specification vehicles.Intake air temperature sensor (IAT Sensor)
This is another resistive sensor, located in the body of
the air cleaner. The resistance varies with changes in
air temperature. The signal from the IAT Sensor is
used to retard the ignition timing if the air temperature
rises above 55°C. If the sensor is disconnected or
failure occurs a default value will be supplied to the
system. The default value selected will represent
normal operating conditions. The fault may not be
evident to the driver, there may be slight power loss in
high ambient temperatures. The fault is indicated by
illumination of the malfunction indicator light (MIL) on
North American specification vehicles.

SFI
1
ADJUSTMENT ENGINE TUNING
Service repair no - 19.22.13
The position of the Idle Air Control (IAC) valve can be
checked using TestBook and adjusted if necessary
through the by-pass screw in the plenum chamber.
The bypass screw is covered by a tamper proof plug
which can be extracted using a self tapping screw.
All vehicles:
1.Ensure air conditioning and all electical loads are
off. Vehicle must be in neutral or park with air
suspension in kneel and disabled.
2.Carry out tuning or base idle setting procedure
as applicable using TestBook.

Mpi
3
DESCRIPTION AND OPERATION Fuel system
ECM
The MEMS system is controlled by the ECM which is
located in the engine compartment.
The ECM is an adaptive unit and can learn the load
and wear characteristics of a particular engine.
The ECM remembers and updates two main engine
requirements when the engine is fully warm:
1.The idle stepper position required to achieve the
specified idle speed.
2.The fuelling change or offset required to achieve
a set oxygen sensor voltage.
The stepper position is used as a reference to update
the amount of stepper motor movement required to
achieve the specified idle speed under all conditions.
The fuelling offset is required to enable the system
when not in closed loop control to provide the correct
fuelling and while in closed loop control to prevent
having to apply excessive adjustments to the fuelling
which can adversely affect the emissions and
driveability.
NOTE: After fitting a different ECM, a full
tune procedure must be carried out using
Testbook.
The ECM inputs and outputs are shown in the table.INPUTS TO MEMS ECM
Crankshaft sensor
Manifold absolute pressure
Coolant temperature sensor
Inlet air temperature sensor
Knock sensor
Oxygen sensor
Throttle potentiometer
Throttle closed
Battery supply
Ignition supply
Diagnostic input
Power earth
Sensor earth
Fuel temperature sensor
Oxygen sensor
Air conditioning switch
OUTPUTS FROM MEMS ECM
Ignition coil
Injectors
Aircon relays
Stepper motor
Temperature gauge
Fuel pump relay (inside relay module)
Main relay (inside relay module)
Diagnostic output

Mpi
5
DESCRIPTION AND OPERATION
Fuel pump
The electric fuel pump, located inside the fuel tank, is
a self-priming centrifugal 'wet' pump, the motor and
pump are filled with fuel.
The fuel pump supplies more fuel than the maximum
load requirement for the engine, so that pressure in
the fuel system can be maintained under all
conditions.
Fuel pressure regulator
The pressure regulator is a mechanical device
controlled by manifold depression and is mounted in
the fuel rail. The regulator ensures that fuel rail
pressure is maintained at a constant pressure
difference to that in the inlet manifold, as manifold
depression increases the regulated fuel pressure is
reduced in direct proportion.
When pressure exceeds the regulator setting excess
fuel is spill returned to the fuel tank swirl pot which
contains the fuel pick-up strainer.
Relay module
The relay module contains the main relay, fuel pump
relay, starter relay and oxygen sensor relay and is
mounted on the ECM mounting bracket.
The main relay is energised when the ignition is
switched on and supplies current to the ECM
The fuel pump relay is energised by the ECM for a
short period when the ignition is switched on, during
cranking and while the engine is running.
The starter relay is energised by the cranking signal
from the ignition switch.
This oxygen sensor relay is energised when the
ignition is switched on and supplies current to the
ECM
Intake air temperature sensor
The intake air temperature sensor is fitted in the side
of the inlet manifold and sends the ECM a signal
relating to air temperature. The ECM uses this signal
in its calculations on air flow.
Inertia switch
The fuel pump circuit incorporates an inertia switch
which in the event of sudden deceleration isolates the
power supply to the fuel pump. The inertia switch is
situated in the engine compartment on the bulkhead
and can, if tripped, be reset by depressing the central
plunger.
WARNING: Check the integrity of the fuel
system before the inertia switch is reset.
Diagnostic connector
A diagnostic connector is provided to enable
diagnosis to be carried out without disturbing the
system electrical connections and to allow the ECM's
ability to store certain faults to be utilised.
Oxygen sensor - Closed-loop emission control
The MEMS Mpi system operates a closed loop
emission system to ensure the most efficient level of
exhaust gas conversion.
An oxygen sensor fitted in the exhaust manifold
monitors the exhaust gases. It then supplies a small
voltage proportional to exhaust oxygen content to the
ECM As the air/fuel mixture weakens, the exhaust
oxygen content increases and so the voltage to the
ECM decreases. If the mixture becomes richer so the
oxygen content decreases and the voltage increases.
The ECM uses this signal voltage to determine the
air/fuel mixture being delivered to the engine, and
adjusts the injector duration to maintain the ratio
necessary for efficient gas conversion by the catalyst.
The oxygen sensor has an integral heating element to
ensure an efficient operating temperature is quickly
reached from cold. The electrical supply for the heater
element is controlled by the oxygen sensor relay.
Fuel temperature sensor
The fuel temperature sensor is inserted in the fuel rail
and measures fuel and fuel rail temperatures. During
engine cranking at high temperatures, the ECM
increases fuel supply, and opens the throttle disc via
the stepper motor to aid hot starting.

CRUISE CONTROL
5
REPAIR ACTUATOR LINK-SETTING - V8i
Service repair no - 19.75.21
NOTE: Setting procedure is carried out at
minimum throttle condition only.
1.Ensure ignition is switched 'OFF'.
2.Check clearance between inside edge of
actuator link and recessed diameter of throttle
lever. Clearance should be 0.2 to 2.0 mm.
Link - adjust
3.Remove link from actuator.
4.Rotate socket joint adjuster as necessary.
5.Refit link to actuator and recheck clearance
between link and lever.
6.With throttle fully open, check a gap of at least
3mm exists between side of link ("A" in
illustration) and side of small spring ("B" in
illustration). Realign link by bending to achieve
correct gap. Recheck clearance at closed
throttle/open throttle. Check link slides smoothly
in groove of throttle lever.

Tdi
1
FAULT DIAGNOSIS ENGINE OVERHEATING
Before conducting any cooling system diagnosis:
See
Description and operation, Engine Cooling
1.Is coolant level correct?
NO - Allow engine to cool, top up level to
expansion tank seam.
YES - Continue.
2.Is drive belt tension correct?
NO -
See ENGINE, Repair, Compressor
Drive Belt
YES - Continue.
3.Is coolant in radiator frozen?
YES - Slowly thaw and drain system.
See
Adjustment, Coolant
NO - Continue.
4.Is air flow through radiator restricted or blocked?
YES - Apply air pressure from engine side of
radiator to clear obstruction.
NO - Continue.
5.Are there any external leaks, from water pump,
engine gaskets, fast idle thermostat or the heater
unit?
YES - Investigate and rectify.
See Adjustment,
Coolant
NO - Continue.
6.Are fan blades fitted correct way round, concave
side towards engine?
NO - Rectify.
YES - Continue
7.Is viscous unit operating correctly?
See
Description and operation, Viscous Fan
NO - Renew.See Repair, Viscous
Coupling, Fan Blades, Pulley and Fan
Cowl
YES - Carry out a pressure test on radiator cap
and system. Check thermostat type,
operation and correct fitting.
See Repair,
Thermostat
If pressure test leads you to suspect coolant
leakage across gaskets, go to check 10,
otherwise: Continue.8.Are the air conditioning fans operating correctly?
See Electrical Trouble Shooting Manual.
NO - Rectify.
YES - Continue.
9.Is temperature sender and gauge giving
accurate readings?
NO - Sustitute parts and compare readings.
YES - Continue.
10.Carry out cylinder pressure test to determine if
pressure is leaking into cooling system causing
over pressurising and loss of coolant.
If problem is not diagnosed, check the coolant system
for engine oil contamination and engine lubrication
system for coolant contamination.
If only the coolant system is contaminated suspect a
cylinder head gasket.
If both systems are contaminated, suspect the
radiator.
If only the lubrication system is contaminated with
coolant, suspect leakage past cylinder liner seals or
cylinder head gasket.

26COOLING SYSTEM
2
FAULT DIAGNOSIS ENGINE RUNS COLD
Before conducting any cooling system diagnosis:
See
Description and operation, Engine Cooling
1.Check operation of viscous unit.See
Description and operation, Viscous Fan
Is viscous unit operating correctly?
NO -
See Repair, Viscous Coupling, Fan
Blades, Pulley and Fan Cowl
YES - Continue.
2.Is thermostat correct type and operating?
See
Repair, Thermostat
If problem is not diagnosed: Continue.
3.Are the air conditioning fans operating
continuously?
YES -
See Electrical Trouble Shooting
Manual.
NO - Continue.
4.Is temperature sender and gauge giving
accurate readings? Substitute parts and
compare readings. If problem is not diagnosed
repeat tests, starting at 1.