oil LAND ROVER DISCOVERY 1995 Workshop Manual

SFI
11
REPAIR FUEL PRESSURE REGULATOR
Service repair no - 19.45.06
Remove
1.Disconnect battery negative lead.
2.Depressurise fuel system.
See Fuel System -
Depressurise
3.Position cloth over fuel feed union, slacken union
to release fuel pressure, then re-tighten union.
4.Release fuel return hose clip. Remove fuel
return hose from regulator connecting pipe.
5.Plug connections.
6.Remove 4 nuts ignition coil bracket to inlet
manifold.
7.Release ignition coil bracket from inlet manifold
studs and place aside.
8.Release regulator connecting pipe from clip.
9.Disconnect vacuum hose from fuel pressure
regulator.
10.Remove 2 bolts securing fuel pressure regulator
to fuel rail.
11.Remove fuel pressure regulator assembly.
12.Remove 'O' ring and spacer ring from fuel
pressure regulator. Discard 'O' ring.
13.Release clip and remove connecting pipe from
regulator.
14.Fit plugs to regulator and rail.

19FUEL SYSTEM
12
REPAIR Refit
15.Ensure locations on fuel pressure regulator and
fuel rail are clean.
16.Fit new spacer ring and 'O' ring to fuel pressure
regulator. Lubricate 'O' ring with silicone grease.
17.Fit pressure regulator assembly to fuel rail.
18.Secure regulator connecting pipe in clip.
19.Secure with bolts. Tighten to
10 Nm.
20.Align ignition coil bracket to inlet manifold studs.
21.Secure ignition coil bracket and fuel rail to inlet
manifold with nuts. Tighten to
8 Nm.
22.Remove plugs.
23.Connect return pipe to regulator connecting pipe.
Secure with clip.
24.Connect vacuum hose to fuel pressure regulator.
25.Remove cloth.
26.Reconnect battery negative lead.
27.Start engine. Check for leaks around fuel
pressure regulator, fuel feed and fuel return
unions.IDLE AIR CONTROL (IAC)
Service repair no - 19.22.54
Remove
1.Disconnect battery negative lead.
2.Disconnect IAC multiplug.
3.Remove 2 bolts securing IAC to plenum.
4.Remove IAC.
5.Remove gasket and discard.
Refit
6.Ensure all mating faces are clean.
7.Using a new gasket, fit IAC to plenum. Secure
with bolts. Tighten to
2.3 Nm.
8.Connect multiplug.
9.Reconnect battery negative lead.

Mpi
1
DESCRIPTION AND OPERATION DESCRIPTION
The Mpi Modular Engine Management System
(MEMS) controls the fuel injection and programmed
ignition systems.
The main features are as follows:
·The Engine Control Module (ECM) controls
programmed ignition and fuel injection. The ECM
incorporates short circuit protection and can
store intermittent faults on certain inputs.
Testbook can interrogate the ECM for these
stored faults.
·The ECM uses the speed/density method of air
flow measurement to calculate fuel delivery. This
method measures the inlet air temperature and
inlet manifold pressure and assumes that the
engine is a calibrated vacuum pump with its
characteristics stored in the ECM
·If certain system inputs fail, the ECM implements
a back-up facility to enable the system to
continue functioning, although at a reduced level
of performance.
·A separate diagnostic connector allows engine
tuning or fault diagnosis to be carried out using
Testbook without disconnecting the ECM
harness connector.
·The ECM harness multiplug incorporates
specially plated pins to minimise oxidation and
give improved reliability.
·The throttle potentiometer requires no
adjustment in service. The following components
supply data for both fuelling and ignition:Ignition system
The ECM determines the optimum ignition timing
based on the signals it receives from the following
sensors:
1.Crankshaft sensor - Engine speed and
crankshaft position.
2.Manifold absolute pressure sensor - Engine load
3.Coolant temperature sensor - Engine
temperature.
4.Manifold absolute pressure sensor - Throttle
closed.
5.Knock sensor - Engine noise and vibration.
MEMS uses no centrifugal or vacuum advance, timing
being controlled by the ECM which is energised by the
main relay, within the relay module. Spark distribution
is achieved by 2 coils mounted at the rear of the
engine and controlled by the ECM.

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

19FUEL SYSTEM
4
DESCRIPTION AND OPERATION
Injectors
The four fuel injectors are fitted between the
pressurised fuel rail and inlet manifold. Each injector
comprises of a solenoid operated needle valve and a
specially designed nozzle to ensure good fuel
atomisation.
Engine coolant temperature sensor
The coolant temperature sensor is mounted in the
thermostat housing and is immersed in the engine
coolant. The sensor is a resistive device in which the
resistance varies with temperature
Throttle housing
The throttle housing is attached to the inlet manifold
via a rubber sandwich plate and incorporates a throttle
disc which is connected to the throttle pedal via the
throttle lever and a cable.
There are two breather pipes; one either side of the
throttle disc. When the engine is running with the
throttle disc open, both pipes are subject to manifold
depression and draw crankcase fumes into the
manifold. When the throttle disc is closed, only the
pipe on the inlet manifold side of the disc is subject to
manifold depression. This pipe incorporates a
restrictor to prevent engine oil being drawn into the
engine by the substantially greater manifold
depression.
Also incorporated in the throttle housing are the
throttle potentiometer and stepper motor.
Throttle potentiometer
The throttle potentiometer is mounted in front of the
throttle housing and is directly coupled to the throttle
disc shaft.
Three wires connect the throttle potentiometer to the
ECM; a 5 volt supply to the potentiometer, an earth
return to the ECM and an output voltage to the ECM
which indicates the rate of throttle disc movement.
Stepper motor
The stepper motor is contained within the throttle
housing and operates a cam and push rod via a
reduction gear. The push rod is in direct contact with
the throttle lever and moves the throttle disc to control
idle and fast idle speed. The stepper motor maximum
movement is 3.75 revolutions accomplished in steps
of 7.5°. The reduction gear converts this into 180°of
cam movement.
The throttle lever has a throttle position setting screw
which rests on the stepper motor operating pin when
the throttle pedal is released and is used to set the
relationship between engine speed and stepper motor
position.
In the side of the throttle housing is a throttle air
bypass bleed screw to provide easier and more
sensitive setting of the stepper motor position at idle.
The stepper motor position is checked using Testbook
and should be within the range of 20 to 40 steps when
the engine is run in. If it is identified as being outside
this range it can be adjusted to within range by turning
the throttle air bypass bleed screw. It is important to
follow Testbook setting procedure when adjusting this
screw to prevent mismatching of throttle body
settings. This ensures that the stepper motor is at the
optimum position within its range for providing further
movement to compensate for changes in engine load
or temperature in accordance with signals from the
ECM
NOTE: The stepper motor and throttle
position setting screws must only be
adjusted when Testbook identifies the
requirement.

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..........................................................

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.

Mpi
1
REPAIR KNOCK SENSOR
Service repair no - 18.30.18
Remove
1.Disconnect multiplug from knock sensor.
2.Remove knock sensor.
Refit
3.Clean mating face of cylinder block.
4.Fit knock sensor. Tighten to
15 Nm
5.Connect multiplug.IGNITION COILS
Service repair no - 18.20.40 - 1 & 4 Cylinders
Service repair no - 18.20.41 - 2 & 3 Cylinders
Remove
1.Disconnect battery negative lead.
2.Disconnect 4 h.t. leads from coils.
NOTE: Mark the position of the h.t. leads
to ensure correct refitment.
3.Disconnect 2 multiplugs from coils.
4.Disconnect crankshaft sensor multiplug.
5.Remove screw securing crankshaft sensor
multiplug to coil bracket.
6.Remove 3 bolts securing coil bracket to bell
housing.
NOTE: Access to the rear bolts is from
under the vehicle.
7.Remove coil assembly.
Refit
8.Position coil assembly to bell housing.
9.Fit 3 bolts and tighten to the correct torque.
10.Secure crankshaft sensor multiplug to coil
bracket with screw.
11.Connect crankshaft sensor multiplug.
12.Connect multiplugs and h.t. leads to coils.
13.Reconnect battery negative lead.

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.

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.