Range Rover P38
BMW DIESEL
5
DESCRIPTION AND OPERATION
Start of injection sensor
The start of fuel injection is registered by this sensor
which is incorporated in No 4 injector.
The sensor consists of a coil which surrounds the
shaft of an extended injection needle.The coil is fed a
DC supply from the ECM which produces a magnetic
field.
When the needle is moved under the influence of fuel
pressure, the magnetic field is disturbed which
induces an AC voltage in the coil. The induced voltage
is registered in the ECM as a reference point for the
start of injection.
1. Coil
2. Injector needle
The ECM uses the input signals from the start of
injection sensor, together with signals from the
crankshaft position sensor, to detect the actual start of
injection angle. The detected actual value is adjusted
by the ECM to a nominal value via the injection timing
solenoid.
Fuel temperature sensor
Fuel temperature is monitored by a sensor located in
the fuel injection pump. This sensor is of the negative
temperature coefficient (NTC) type, designed to
reduce its resistance with increasing temperature.
When the system is operating, the ECM regularly
checks the sensor resistance. As fuel density varies
with temperature, the information received is used to
calculate the correct quantity of fuel to inject.
Engine coolant temperature sensor (ECT sensor)
The temperature of the engine coolant is monitored by
a ECT sensor located on the cylinder head.
The ECT sensor is of the NTC type and is similar in
operation to the fuel temperature sensor previously
described.
The ECM uses this information to adjust the basic
injection timing and quantity values for all operating
conditions.
