Range Rover 2. Electrical Manual - part 5

INTRODUCTION

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SEQUENTIAL MULTIPORT FUEL INJECTION (SFI–V8)

CIRCUIT OPERATION

CIRCUIT OPERATION

Sensors

Engine Fuel Temperature Sensor (X128)

This is a resistive sensor, located on the fuel rail and
measuring the temperature of the rail rather than the
fuel. The signal is used to increase the injection
pulse times when undergoing hot restarts. When the
fuel is hot, vaporisation occurs in the rail and a
“bubble” could form within the injectors. Increasing
the pulse times flushes the “bubbles” away and cools
the fuel rail with fuel from the tank.

Knock Sensors (X309, X310)

The knock sensor is a “Piezo–electric
accelerometer,” i.e. it produces an output voltage
proportional to mechanical vibration produced by the
engine. The Engine Control Module (ECM) (Z132)
receives the signal, filters out any noise and
calculates if the engine is knocking. Due to the cam
and crank signals supplying information regarding
the position of the engine in it’s cycle, the ECM
(Z132) can work out exactly which cylinder is
knocking and retards the ignition on that particular
cylinder until the knock disappears. It then advances
the ignition again to find the optimum ignition point
for that cylinder for those conditions (i.e. fuel type,
air temperature etc.). The ECM (Z132) will be able to
adjust cylinder timing for knock simultaneously, so
that all eight cylinders could have different advance
angles at the same time.

Coolant Temperature Sensor (X126)

A temperature dependant resistive metal component
is the major constituent of this sensor, i.e. the
resistance of the metal strip varies quite
considerably with temperature. The coolant sensor
signal is vital to correct engine operation, as the
injected fuel quantity is dependant upon the engine
temperature, i.e. richer mixture at low temperatures.

Intake Air Temperature Sensor (X311)

This is a resistive sensor, i.e. the change in
resistance is related to change in air temperature.
The signal from the Intake Air Temperature Sensor
(X311) is used to retard the ignition timing if the air
temperature rises above 55

Crankshaft Position Sensor (X250)

The Crankshaft Position Sensor (X250) is a very
important sensor, as the signal it produces tells the
ECM (Z132) that the engine is turning, how fast it is
turning and at which stage the engine is at in the

cycle. The crank signal is the basis of the fuel
injection and coil firing times.

Camshaft Position Sensor (Z262)

This is a Hall Effect sensor producing one pulse for
every two revolutions. The Signal is used in two
areas: Injector timing corrections for fully sequential
fuelling and active knock control.

Camshaft operation is essential to continue normal
ignition, i.e. actuate the fuel injectors in the normal
sequential order, timing the injection correctly with
respect to top dead centre. In this way the sequential
fuelling will either be correct, or one engine
revolution out of synchronisation.

SEQUENTIAL MULTIPORT FUEL INJECTION (SFI–V8)

CIRCUIT OPERATION

Mass Air Flow Sensor (X105)

The sensing element of a Mass Air Flow Sensor
(X105) is a “hot wire anomometer” consisting of two
wires; one heated, one not. The air flows across the
wires, cooling the hot wire and thereby altering its
resistance. The ECM (Z132) measures this change
in resistance and so calculates the amount of air
flowing into the engine.

If the Mass Air Flow Sensor (X105) fails, the engine
will start and then die as the engine reaches 550 rpm
before the ECM (Z132) looks for the Mass Air Flow
Sensor (X105) signal.

Throttle Position Sensor (X171)

This sensor is a variable resistor. The signal informs
the ECM (Z132) of the actual position of the throttle
plate. Failure of the Throttle Position Sensor (X171)
will result in poor idle and lack of throttle response. If
the Throttle Position Sensor (X171) fails in the
“closed” mode, then the engine will only rev up to
1740 rpm when the ECM (Z132) will initiate “over run
fuel cut–off”.

Heated Oxygen Sensors (X139, X160, X289, X290)

The heated oxygen sensor consists of a titanium
metal sensor surrounded by a gas–permeable
ceramic coating. Oxygen in the exhaust gas diffuses
through the ceramic coating on the sensor and
reacts with the titanium wire, altering the resistance
of that wire. From this change in resistance, the
ECM (Z132) can calculate the percentage of oxygen
in the exhaust gas and adjust the injected fuel
quantity that as to achieve the correct air/fuel ratio.
This reduces the emissions of Carbon Monoxide
(CO), Hydrocarbons (HC) and oxides of Nitrogen
(NOX) to acceptable levels.

Presently, two heated oxygen sensors are used, one
in each exhaust down pipe just before the catalyst.

In the event of sensor failure, the system will default
to ”open loop”. Operation and fuelling will be
calculated using signals from the remaining ECM
inputs. The fault is indicated by illumination of the
malfunction indicator lamp (MIL). ECM diagnostics
also uses heated oxygen sensors to detect catalyst
damage, misfire and fuel system faults.

North American vehicles have two extra heated
oxygen sensors mounted one after each catalyst.
These are used to determine whether the catalysts
are operating efficiently.

Idle Air Control Valve (M112)

The Idle Air Control Valve (M112) controls the idle
speed of the engine by moving the plunger a set
distance, known as a step. Fully open is zero steps
and fully closed is 180 steps. The motor moves each
step by sequentially changing the polarity to each of
the two coils.

SEQUENTIAL MULTIPORT FUEL INJECTION (SFI–V8)

CIRCUIT OPERATION

Ignition Coils (Z261)

The ignition system on the petrol engine consists of
a “DIS” format, a Direct Ignition System, comprising
of four double ended coils operating on the “wasted
spark” technique. The circuit to each coil is
completed via switching within the ECM (Z132),
allowing the coil to charge up and then fire. It
produces sparks in two cylinders simultaneously, one
cylinder on the compression stroke and one on the
exhaust stroke. Due to relatively easy ionisation of
the fuel/air mixture in the cylinder under
compression, the coil will dissipate more energy in
that cylinder than the other, so very little energy is
wasted in the system.

Failure of a coil will result in lack of sparks in two
cylinders (coil 1 feeds cylinders 1/6, coil 2 feeds
cylinders 5/8, coil 3 feeds cylinders 4/7 and coil 4
feeds cylinders 2/3). This results in a misfire.

Injector/Injectors

The fuel injection system used is a “sequential
multi–point” system (SFI) i.e. one injector for each
cylinder (compared to “single point” injection or
throttle body injection which uses one injector only).
A fuel injector consists of a small solenoid which is
activated by the ECM (Z132), allowing fuel to pass
into the combustion chamber. Due to the fuel
pressure in the rail and the shape of the injector
orifice, the fuel squirts into the cylinder in a fine
spray to aid combustion.

Relays

The engine management system uses four relays:

– Starter motor, ECM (Z132) power supply (main
relay), ignition and fuel pump, all located within the
fusebox.

Main Relay

This relay supplies the power feed to the ECM
(Z132) with a tap off to feed the fuel injectors and air
flow meter. This relay is controlled by the ECM
(Z132) itself, so that the ECM (Z132) remains
powered up after the ignition is removed and the
ECM (Z132) can record all temperature readings and
motorise the Idle Air Control Valve (M112) to the fully
open position. This is known as the “ECM (Z132)
power down routine”. Failure of this relay will cause
the ECM (Z132) to not be switched on, resulting in
absence of fuel and spark and therefore a failed
start.

Ignition Relay

This relay is ignition key controlled and supplies a
feed to the coils, evaporative emission canister
purge valve and heated oxygen sensor. When the
ignition key is turned off, supply to the coils is cut
immediately.

Starter Motor Relay

This relay is also ignition key controlled and is
activated with the key in the ignition III position only.
Releasing the key after cranking cuts supply to the
relay and switches off the starter motor.

Fuel Pump Relay

This relay is fed from the ignition relay and controlled
by the ECM (Z132). It is pulled in on ignition II
position to prime the fuel system. If the key remains
in the ignition II position, then the relay falls out after
a few seconds, precisely when determined by the
ECM (Z132).

Engine Control Module (ECM) (Z132)

If the ECM (Z132) itself is not working, the entire
engine management system will cease to operate:
no fuel, sparks, tacho reading, etc.

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