LAND ROVER DISCOVERY 1995 Workshop Manual

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
1
ADJUSTMENT THROTTLE CABLE
Adjust
NOTE: Use diagnostic equipment to
ensure that the throttle potentiometer and
stepper motor are synchronised before
adjusting the throttle cable.
Ensure that the cable is correctly routed and located.
1.Switch ignition on, wait 5 seconds and switch
ignition off to ensure stepper motor is in setting
position.
2.Loosen throttle cable adjustment nut and locknut
from abutment bracket.
3.Hold cam in "throttle closed" position and rotate
cable adjustment nut until a gap of 2mm exists
between the nut and abutment bracket.
4.Tighten cable locknut to contact abutment
bracket.
5.Using two wrenches tighten nuts onto abutment
bracket.
6.Operate throttle pedal and ensure throttle opens
fully.

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.

19FUEL SYSTEM
2
REPAIR COOLANT TEMPERATURE SENSOR
Service repair no - 18.30.10
Remove
1.Position drain tin below coolant pump hose.
2.Disconnect sensor multiplug.
3.Release harness clip and harness.
4.Remove sensor.
Refit
5.Clean sensor.
6.Fit sensor and tighten to the correct torque.
7.Position harness and secure with clip.
8.Connect multiplug.
9.Top-up cooling system.CRANKSHAFT SENSOR
Service repair no - 18.30.12
Remove
1.Position vehicle on ramp [hoist].
2.Disconnect multiplug from crankshaft sensor
flylead.
3.Remove screw, release lead from bracket.
4.Raise ramp [hoist].
5.Remove 2 bolts securing crankshaft sensor.
6.Remove crankshaft sensor.
Refit
7.Clean crankshaft sensor and mating surface of
backplate.
8.Fit crankshaft sensor, fit bolts. Tighten to
7Nm
9.Lower vehicle.
10.Position lead to bracket, fit and tighten screw.
11.Connect multiplug

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.

19FUEL SYSTEM
4
REPAIR CHARCOAL CANISTER
Service repair no - 17.15.13
Remove
1.Disconnect multiplug from purge valve.
2.Release clip and disconnect hose from purge
valve.
3.Release clip and disconnect fuel tank hose from
charcoal canister.
4.Unscrew bolt to release securing strap and
remove charcoal canister.
Refit
5.Fit charcoal canister and secure strap.
6.Connect fuel tank hose to charcoal canister and
secure clip.
7.Connect hose to purge valve and secure clip.
8.Connect multiplug to purge valve.THROTTLE CABLE
Service repair no - 19.20.06
Remove
1.Loosen 2 nuts securing throttle cable to
abutment bracket.
2.Release throttle cable from throttle lever.
3.Remove footwell closing panel.
4.Release split [cotter] pin from throttle pedal
clevis pin.
5.Remove clevis pin and release cable from
throttle pedal.

Mpi
5
REPAIR 6.Remove nut securing throttle cable bracket to
brake servo and release cable.
7.Release grommet from bulkhead and withdraw
cable.
8.Locate cable in bulkhead.
9.Connect cable to throttle pedal.
10.Connect cable to cam.
11.Adjust throttle cable.THROTTLE POTENTIOMETER
Service repair no - 19.22.49
Remove
1.Disconnect throttle potentiometer multiplug.
2.Remove 2 screws securing throttle
potentiometer, remove potentiometer.
Refit
3.Clean mating faces of throttle potentiometer and
throttle housing.
4.Fit throttle potentiometer, fit and tighten screws.
CAUTION: Ensure throttle potentiometer is
correctly engaged with throttle cam and
that wiring outlet faces downwards.
5.Connect multiplug.
6.Check with diagnostic equipment.

19FUEL SYSTEM
6
REPAIR INTAKE AIR TEMPERATURE SENSOR
Service repair no - 18.30.09
Remove
1.Disconnect multiplug from temperature sensor.
2.Remove sensor from inlet manifold.
Refit
3.Clean sensor threads and mating face.
4.Fit sensor to inlet manifold. Tighten to
7Nm
5.Connect multiplug to sensor.PURGE CONTROL VALVE
Service repair no - 17.15.39
Remove
1.Disconnect multiplug from purge control valve.
2.Release clip and disconnect hose from valve.
3.Release valve from charcoal canister.
4.Remove valve.
5.Discard 'O' ring.
Refit
6.Clean valve and valve location.
7.Position and secure valve to charcoal canister.
8.Connect hose to purge valve and secure with
clip.
9.Connect multiplug to valve.

Mpi
7
REPAIR FUEL RAIL AND INJECTORS
Service repair no - 19.60.04 - Rail
Service repair no - 19.60.10 - Injectors
Remove
1.Remove inlet manifold chamber gasket.
See
MANIFOLD AND EXHAUST SYSTEM, Repair,
Manifold Chamber Gasket - Mpi
2.Remove pressure regulator.
3.Remove 4 bolts securing fuel feed hose flange
stiffening bracket, remove stiffening bracket.
4.Release fuel feed hose from fuel rail.
5.Discard 'O' ring.
6.Disconnect 4 injector multiplugs.
7.Move injector harness aside.
8.Remove 2 bolts securing fuel rail to inlet
manifold.
9.Release 4 injectors from inlet manifold.
10.Remove fuel rail complete with injectors.
11.Discard outlet 'O' rings from injectors.
12.Fix protective cap to each injector.
Do not carry out further dismantling if component
is removed for access only.
13.Remove clip(s) securing injector(s) to fuel rail.
14.Remove injector(s).
15.Discard inlet 'O' ring(s) from injector(s).
16.Remove fuel temperature sensor.