Range Rover P38
19
FUEL SYSTEM
NEW RANGE ROVER
4
DESCRIPTION AND OPERATION
Input devices
Input devices of the DDE system comprise the
following:
Crankshaft position sensor
Start of injection sensor
Fuel temperature sensor
Coolant temperature sensor
Intake air temperature sensor
Manifold absolute pressure sensor
Vehicle speed signal
Throttle position sensor
Servo unit potentiometer (drive potentiometer) on
quantity servo control unit
Clutch switch
Brake switches
Cruise control selector (if fitted)
Crankshaft position sensor (CKP sensor)
Attached to the flywheel of the engine are six position
pins. These are equally spaced around the crankshaft
circumference at 60 degree intervals.
To determine engine speed and crankshaft position,
an inductive CKP sensor is mounted on the crankcase
adjacent to the flywheel. The CKP sensor consists of
a body containing a coil and a permanent magnet
which provides a magnetic field. The CKP sensor is
situated so that an air gap exists between it and the
position pins. Air gap distance is critical for correct
operation.
1. Sensor
2. Flywheel
As the flywheel rotates, position pins pass the CKP
sensor and disturb the magnetic field, inducing
voltage pulses in the coil. The pulses are transmitted
to the ECM.
When the flywheel rotates one complete revolution,
six pulses are transmitted to the ECM. The ECM
determines engine speed by calculating how many
pulses occur within a given time. The output from the
CKP sensor is also used, in conjunction with the start
of injection sensor, to determine and control ignition
timing.
The flywheel position pins are spaced so that at TDC,
one pin is 40 degrees before TDC while the other is
20 degrees after TDC as shown. To determine which
pulse represents 40 degrees before, or 20 degrees
after TDC, the control unit requires additional
information from the start of injection sensor.
