1995 LAND ROVER DISCOVERY engine

Mpi
9
DESCRIPTION AND OPERATION SYSTEM OPERATION
Ignition on
When the ignition is switched on, voltage is applied to
ECM pin 11. The ECM then switches on the main
relay by supplying an earth path at pin 4. This allows
battery voltage to pass to ECM pin 28, to the four
injectors and through the ignition coil to ECM pin 25.
In addition, the fuel pump relay is switched on by the
ECM supplying an earth path on pin 20. Voltage is
applied through the inertia switch to the fuel pump.
The pump runs for a short period to pressurise the
fuel rail. The fuel pressure regulator will open at its
maximum setting and excess fuel is spill returned to
the tank.
The ECM determines the amount of stepper motor
movement from the following signals:
·Engine coolant temperature data at pin 33.
·Inlet air temperature data at pin 16.
·Throttle potentiometer data at pin 8.
·Engine speed data at pins 31 and 32.
·Manifold absolute pressure data (via pipe from
manifold).
·Battery voltage at pin 28.
·Ignition signal at pin 11.
If one or more of the following inputs fail, the ECM will
substitute the back-up values shown to maintain
driveability.
Input Back-up value
Coolant temperature Idle Speed controlled until
engine is fully warm. 60°Cat
speeds above idle.
Inlet air temperature Derived from engine speed and
engine load.
Manifold absolute Derived from engine speed and
pressure throttle position.
Starter operation
Whilst the starter relay is energised, battery voltage is
applied to the starter motor solenoid. The solenoid
also energises and supplies battery voltage directly to
the starter motor.
Ignition is controlled by the ECM switching the low
tension circuit via pin 25.
The ECM provides an earth signal on pins 24, 23, 26
and 1 for the period the injectors are required to be
open, the injector solenoids are energised
(simultaneously on naturally aspirated models) and
fuel is sprayed into the manifold onto the back of the
inlet valves. The ECM carefully meters the amount of
fuel injected by adjusting the injector opening period
(pulse width). During cranking, when the engine
speed is below approx. 400 rev/min, the ECM
increases the injector pulse width to aid starting. The
amount of increase depends upon coolant
temperature. To prevent flooding, injector pulses are
intermittent i.e. 24 on then 8 pulses off.
Idling
After start enrichment is provided at all temperatures
immediately cranking ceases. The ECM controls the
enrichment by increasing injector pulse width. The
enrichment decays in relation to the rising coolant
temperature.
Provided the ECM is receiving a signal that the engine
speed is close to the idle speed set point, the ECM
will implement idle speed control.
The ECM activates a unipolar stepper motor acting
directly on the throttle lever. Idle speed response is
improved by the ignition system advancing or
retarding the timing when load is placed on, or
removed from the engine.
If, during engine idle, the load on the engine is
increased sufficiently to cause engine speed to fall,
the ECM will sense this via the crankshaft sensor and
instantly advance the ignition timing to increase idle
speed and then energise the stepper motor to open
the throttle disc thus maintaining the idle speed.
Finally the ignition timing is retarded to its nominal
value.
The ECM monitors battery voltage and, if voltage falls
sufficiently to cause fluctuations in injector pulse
widths, it increases the injector pulse widths to
compensate.
On return to idle, the ECM will implement a slightly
higher idle speed to prevent the engine stalling.

19FUEL SYSTEM
10
DESCRIPTION AND OPERATION
Driving
When the throttle pedal is depressed, the ECM
implements the cruise air/fuel ratio map. During
driving the ECM continually monitors inlet air
temperature and engine speed and load for it's air
flow calculations, together with coolant temperature
for any temperature corrections. Additional inputs are
throttle potentiometer for acceleration and throttle
pedal switch for cruise/idle fuel map selection and
over-run fuel cut-off.
Acceleration enrichment
When the throttle pedal is depressed, the ECM
receives a rising voltage from the throttle
potentiometer and detects a rise in manifold pressure
from the manifold absolute pressure sensor. The ECM
provides additional fuel by increasing the normal
injector pulse width and also provides a small number
of extra injector pulses on rapid throttle openings.
Over-run fuel cut-off
The ECM implements over-run fuel cut-off when the
following signals are received.
·Throttle disc closed.
·Engine speed is above 2000 rev/min - engine at
normal operating temperature.
Fuel is reinstated progressively when any of the
above signals cease.
Over-speed fuel cut-off
To prevent damage at high engine speeds the ECM
inhibits the earth path for the injectors, cutting off
injection. As engine speed falls, injection is reinstated.
Ignition switch off
When the ignition is switched off, the ECM will keep
the main relay energised for approx. 30 seconds while
it drives the stepper motor to the 35 step position for
the next engine start.

Mpi
3
REPAIR FUEL TEMPERATURE SENSOR
Service repair no - 18.30.08
Remove
1.Disconnect fuel temperature sensor multiplug.
2.Remove fuel temperature sensor.
3.Discard sealing washer.
Refit
4.Clean mating face of fuel rail.
5.Fit a new sealing washer to sensor.
6.Fit temperature sensor. Tighten to
7Nm
7.Connect fuel temperature sensor multiplug.MEMS ENGINE CONTROL MODULE (ECM)
Service repair no - 18.30.01
Remove
1.Remove 3 bolts securing ECM.
2.Disconnect 2 multiplugs from ECM.
3.Disconnect vacuum hose from ECM.
4.Remove ECM.
5.Collect ECM spacers (LHD only)
Refit
6.Position ECM and spacers to wing [fender].
7.Connect vacuum hose to ECM.
8.Connect multiplugs to ECM.
9.Position ECM to mounting.
10.Fit bolts and tighten.

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.

CRUISE CONTROL
1
FAULT DIAGNOSIS ROAD TEST
CAUTION: Do not engage cruise control
when vehicle is being used in low transfer
gear or reverse.
WARNING: The use of cruise control is not
recommended on winding, snow covered
or slippery roads or in heavy traffic
conditions where a constant speed cannot be
maintained.
1.Start engine, depress main control switch to
actuate cruise control system. Accelerate to
approximately 50 km/h, (30 mph), operate
'set/acc'switch, immediately release switch,
remove foot from accelerator pedal. Vehicle
should maintain speed at which'set/acc'switch
was operated.
2.Operate'set/acc'switch and hold at that
position, vehicle should accelerate smoothly until
switch is released. Vehicle should now maintain
new speed at which'set/acc'switch was
released.
3.Momentarily touch and release'set/acc'switch,
vehicle speed should increase 1.6 km/h (1 mph)
for each touch. Note that five touches will
increase speed 8 km/h (5 mph).
4.Apply'res/decel'switch while vehicle is in cruise
control mode, cruise control should disengage.
Slow to approximately 55 km/h, (35 mph)
operate'res/decel'switch, immediately release
switch and remove foot from accelerator, vehicle
should smoothly accelerate to previously set
speed. Increase speed using accelerator pedal,
release pedal, vehicle should return to previously
set speed.
NOTE: The cruise control system fitted to
the diesel engine is not as responsive as
that fitted to the petrol engine, due to the
characteristics of diesel engines. Therefore, at
speeds below approx. 65 km/h (40 mph), the
vehicle speed may drop when cruise is selected
and then slowly regain the 'set' speed.5.Operate brake pedal, cruise control system
should immediately disengage returning vehicle
to driver control at accelerator pedal. Operate
'res/decel'switch, vehicle should accelerate to
previously set speed without driver operation of
accelerator pedal.
6.Operate'res/decel'switch and allow vehicle to
decelerate to below 42 km/h, (26 mph). Operate
'res/decel'switch, cruise control system should
remain disengaged.
7.Operate'set/acc'switch below 40 km/h, (28
mph), cruise control system should remain
disengaged. Accelerate, using accelerator pedal
to above 45 km/h, (28 mph), operate'res/decel'
switch, and remove foot from accelerator pedal,
vehicle should smoothly adjust to previously
memorised speed.
8. Automatic vehicles- select neutral, system
should disengage.Manual vehicles- depress
clutch, system should disengage.
9.Cruise at 80 km/h (50 mph), declutch, select
neutral, remove foot from clutch. Operate
'res/decel'switch. Engine should rev to 5000
rev/min, cruise control disengages, engine
returns to idle.
10.Engage forward gear. Operate'res/decel'
switch. Remove foot from accelerator. Speed
should accelerate to previous set speed.
11.Depress main control switch in control system
should immediately disengage and erase
previously set speed from ECU memory.
See
Electrical Trouble Shooting Manual.
ELECTRICAL TESTS
Electrical functionality can be checked using
TestBook.
CABLE SETTING - TDi AUTOMATIC MODELS
1.An incorrectly adjusted kickdown cable can
prevent correct operation of the cruise control
system.
See AUTOMATIC GEARBOX,
Adjustment, kickdown cable adjustment.

Tdi
1
DESCRIPTION AND OPERATION ENGINE COOLING
Description
The Tdi engine uses a pressurized cooling system
and cross flow radiator which is supplied from a
separate header tank. The radiator assembly is in
three sections. The largest section is for engine
coolant and the other two sections which are cast in
aluminium, are the engine oil cooler and the turbo
charger intercooler.
A belt driven viscous fan and centrifugal water pump
is located in the front of the cylinder block. Hot coolant
is supplied to the heater through hoses. Two small
diameter air purge hoses connect the top of the
radiator and cylinder head water gallery, to the header
tank.
Coolant circulation (engine cold)
1. Cross flow radiator
2. Header tank
3. Viscous fan
4. Heater hoses
5. By pass hose and engine thermostat
6. Air purge hoses
7. Coolant pumpCOOLANT CIRCULATION
Operation
When the engine is started from cold the thermostat
prevents any coolant circulation through the radiator
by closing off the top hose. During the engine warm
up period, the water pump, pumps coolant towards
the rear of the cylinder block around each of the
cylinders. Coolant as it is heated rises through ports in
the cylinder block and head gasket, into the cylinder
head.The coolant flows forwards to the thermostat,
by-pass port and radiator top hose connection.
Start from cold (thermostat closed)
While the thermostat is closed, coolant circulates
around the cylinder block and cylinder head via the
by-pass.
Engine warm (thermostat open)
When the engine reaches normal running temperature
the thermostat closes off the by-pass and opens the
flow to the top of the radiator.

26COOLING SYSTEM
2
DESCRIPTION AND OPERATION VISCOUS FAN
Description
The viscous drive unit for the engine cooling fan,
provides a means of controlling the speed of the fan
relative to the running temperature of the engine. The
viscous unit is a type of fluid coupling, which drives
the fan blades through the medium of a special
'silicone fluid' injected into the unit during
manufacture.
1. Drive in from water pump spindle
2. Drive out to fan blades
3. Bi-metalOperation
The viscous unit consists of two principal components:
An inner member 1 which is secured to water pump
spindle and is driven by the fan belt.
An outer member 2 which has the fan blades
attached, houses the working parts and is driven
through the medium of the viscous fluid.
The inner and outer members have interlocking
annular grooves machined in each, with a small
running clearance 3 to allow the silicone fluid to
circulate through the valve plate 4.
The unit also contains a valve 5 which is controlled by
an external bi-metal thermostat 6.
Starting engine from cold
During the time the engine is at rest the silicone fluid
drains down, half filling chambers A and B. Thus when
the engine is first started sufficient fluid is present in
chamber A to provide a positive drive between the
members, as is evident by the initial noise of the fan.
However within a very short period of time, after
starting the engine, the fan speed and noise will
decline indicating that the fluid is being centrifuged
into chamber B (as seen in RR3757M) causing the
drive to slip.