low oil pressure LAND ROVER DISCOVERY 1995 Owner's Manual

12ENGINE
14
REPAIR Refit
1.Clean sump, remove all traces of gasket from
mating faces of sump and cylinder block.
Visually check sump for damage.
2.Apply beads of RTV sealant to front main
bearing cap.
3.Position new gasket to sump, ensuring that
location pips on gasket are located in sump.
Check gasket lays flat on sump flange.
4.Fit sump. Fit bolts, ensuring that longest bolt is
inserted at position 7.
5.Working around the sump in the sequence
illustrated, tighten the bolts to the stage 1 torque
figure. Then, in the same sequence, tighten the
bolts to the stage 2 torque figure.
NOTE: For torque values.See
Specifications, torque, Torque Values
6.Fill engine with oil.CYLINDER HEAD GASKET
Service repair no - 12.29.01
Remove
1.Disconnect battery negative lead.
2.Position absorbent cloth around fuel pipe to fuel
rail union. Unscrew union to relieve pressure.
CAUTION: Plug the connections.
WARNING: Do not carry out the next
instruction until the coolant is cool to
avoid personal injury from scalding.
3.Release clip and disconnect radiator bottom
hose, allowing coolant to drain into a suitable
container.

Mpi
1
SPECIFICATIONS, TORQUE TORQUE VALUES
NOTE: Torque wrenches should be regularly checked for accuracy to ensure that all fixings are
tightened to the correct torque.
Nm
ENGINE
Timing belt upper cover bolts 5......................................................................
Timing belt centre cover bolts 5.....................................................................
Timing belt lower cover bolts 5......................................................................
Crankshaft pulley centre bolt 85.....................................................................
Crankshaft pulley to timing gear bolts 10........................................................
Tensioner pulley bolt 30..................................................................................
Spark plugs 27................................................................................................
Timing belt upper backplate bolts 10..............................................................
Camshaft gear bolts 65...................................................................................
Exhaust camshaft rear oil seal cover plate bolts 10........................................
Inlet camshaft rear oil seal cover plate bolts 10..............................................
Crankshaft rear oil seal housing bolts 10........................................................
Engine sump bolts
Stage 1 3...............................................................................................
Stage 2 10..............................................................................................
Bell housing nuts 40........................................................................................
L.H. and R.H. engine mounting nuts 85..........................................................
Exhaust manifold to downpipe nuts 10...........................................................
Exhaust downpipe to silencer box nuts 30......................................................
Air conditioning compressor to engine block bolts 45.....................................
Cylinder head bolts
Stage 1 45..............................................................................................
Stage 2 80..............................................................................................
Stage 3 - Further 90°
Camshaft cover bolts 10.................................................................................
Knock sensor 15.............................................................................................
Ignition coil bracket bolts 25............................................................................
Coolant temperature sensor 15......................................................................
Crankshaft sensor bolts 7..............................................................................
Fuel temperature sensor 7.............................................................................
Intake air temperature sensor 7.....................................................................
Fuel rail to inlet manifold bolts 10...................................................................
Fuel feed hose stiffening bracket bolts 7.......................................................
Throttle housing mounting nuts 7...................................................................
Fuel pressure regulator steady bracket bolts 7..............................................
Oxygen sensor 55...........................................................................................

EMISSION CONTROL
1
DESCRIPTION AND OPERATION REV: 09/95 EMISSION CONTROL
Three systems are used to control the vehicle
atmospheric emissions these are:
Engine crankcase fume emissions.
Fuel tank Evaporative emissions
Engine exhaust gas emissions.
Crankcase ventilation system - 3.9 MFi models
only
The crankcase ventilation system which is an integral
part of the air supply to the engine combustion
chambers, is often overlooked when diagnosing
problems associated with engine performance. A
blocked ventilation pipe or filter or excessive air leak
into the inlet system through a damaged pipe or
leaking gasket can effect the mixture, performance
and economy of the engine.
1. Three way connector
2. Air filter
3. Oil separatorThe purpose of the crankcase ventilation system is to
ensure that any noxious gas generated in the engine
crankcase is rendered harmless by burning in the
combustion chambers as follows:
Oil laden noxious gas in the engine crankcase is
drawn through an oil separator 3 located on the right
cylinder head rocker cover, where the oil is separated
and returned to the sump. The gas flows through a
restrictor in the three way connection 1 and into the
inlet plenum chamber where it is drawn into the
combustion chambers and burned. The volume of
fresh air which is drawn from the atmospheric side of
the throttle butterfly to mix with the gas, depends on
the position of the throttle and the engine speed.
The air filter 2 fitted to the left cylinder head rocker
cover, must be maintained in clean condition to
ensure sufficient air enters the crankcase under
varying throttle openings and manifold depression, to
prevent excessive crankcase pressure or depression
developing.

19FUEL SYSTEM
2
DESCRIPTION AND OPERATION REV: 09/95 ENGINE MANAGEMENT SYSTEM COMPONENT
LOCATION - PRE ADVANCED EVAPS
1. Engine control module
2. Ignition coils
3. Fuel pressure regulator
4. Mass air flow sensor
5. Relay module
- Main relay
- Fuel pump relay
6. Engine coolant temperature sensor
7. Camshaft position sensor
8. Throttle position sensor

SFI
5
DESCRIPTION AND OPERATION REV: 09/95 Engine fuel temperature sensor (EFT Sensor)
This is another resistive sensor. Located on the fuel
rail it measures temperature of the rail rather than the
fuel. The resistance varies with changes in
temperature. The signal is used to increase the
injection pulse time when undergoing hot restarts.
When the fuel is hot, vapourisation occurs in the rail
and bubbles can occur in the injectors. Increasing the
pulse time flushes the bubbles away, and cools the
fuel rail with fuel from the tank. 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.
Knock sensors
The knock sensor produces an output voltage in
proportion to mechanical vibration caused by the
engine. A sensor is located in each cylinder bank
between 2/4 and 3/5 cylinders. The ECM calculates if
the engine is knocking due to camshaft and
crankshaft sensor signals regarding the position of the
engine in the cycle. The ECM can also work out
exactly which cylinder is knocking and retards the
ignition on that particular cylinder until the knock
disappears. It then advances the ignition to find the
optimum ignition timing for that cylinder. The ECM can
adjust the timing of each cylinder for knock
simultaneously. It is possible that all eight cylinders
could have different advance angles at the same time.
If the camshaft sensor fails, the knock sensor will
continue to work, but as the engine may be running
one revolution out of sychronisation the ECM may
retard the wrong cylinder of the pair e.g. 1 instead of
6. If the knock sensor fails engine knock will not be
detected and corrected. The fault is indicated by
illumination of the malfunction indicator light (MIL) on
North American specification vehicles.Ignition coils
The electronic ignition system uses four double ended
coils. They are mounted on a bracket fitted to the rear
of the engine. The circuit to each coil is completed by
switching within the ECM, allowing each coil to charge
up and fire. Sparks are produced in two cylinders
simultaneously, one on compression stroke, the other
on exhaust stroke. Note that coil 1 feeds cylinders 1
and 6, coil 2 feeds cylinders 5 and 8, coil 3 feeds
cylinders 4 and 7, and coil 4 feeds cylinders 2 and 3.
Due to the ease of combustion in the cylinder on the
compression stroke, more energy is dissipated in that
cylinder. Coil failure will result in a lack of sparks and
misfire in the affected cylinders. The fault is indicated
by illumination of the malfunction indicator light (MIL)
on North American specification vehicles.
Injectors
A multiport fuel injection system (MFI) is used, one
injector per cylinder. Each injector consists of a small
solenoid which is activated by the ECM to allow a
metered amount of fuel to pass into the combustion
chamber. Due to the pressure in the fuel rail and the
shape of the injector orifice, the fuel squirts into the
cylinder in a fine spray to aid combustion. In the
unlikely event of injector failure a misfire will occur as
there will be no fuel to the affected cylinder. The fault
is indicated by illumination of the malfunction indicator
light (MIL) on North American specification vehicles.

19FUEL SYSTEM
8
DESCRIPTION AND OPERATION ADD: 09/95 ENGINE MANAGEMENT SYSTEM COMPONENT
LOCATION - ADVANCED EVAPS
1.Engine control module (ECM)
2.Ignition coils
3.Fuel pressure regulator
4.Mass air flow (MAF) sensor
5.Relay module
- Main relay
- Fuel pump relay
6.Engine coolant temperature (ECT) sensor
7.Camshaft position (CMP) sensor
8.Throttle position (TP) sensor

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
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.

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.

V8i
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, Drive Belt -
Check Tension
YES - Continue.
3.Is ignition timing correct?
NO -
See ELECTRICAL, Adjustment,
Ignition Timing
YES - Continue.
4.Is coolant in radiator frozen?
YES - Slowly thaw and drain system.
See
Adjustment, Coolant Requirements
NO - Continue.
5.Is air flow through radiator restricted or blocked?
YES - Apply air pressure from engine side of
radiator to clear obstruction.
NO - Continue.
6.Are there any external leaks, from water pump,
engine gaskets or the heater unit?
YES - Investigate and rectify.
See Adjustment,
Coolant Requirements
NO - Continue.
7.Are fan blades fitted correct way round, concave
side towards engine?
NO - Rectify.
YES - Continue.8.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 11,
otherwise: Continue.
9.Are the air conditioning fans operating correctly?
See Electrical Trouble Shooting Manual.K5
NO - Rectify.
YES - Continue.
10.Is temperature sender and gauge giving
accurate readings?
NO - Substitute parts and compare readings.
YES - Continue.
11.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 the coolant only, or both systems are contaminated,
suspect cylinder head gaskets or radiator.
If only the lubrication stystem is contaminated with
coolant, suspect inlet manifold or front cover gaskets.