JAGUARS-TYPEFuel System
41
JOL.062
INERTIA SWITCH operating fuel level sender assembly mounted on
the respective module assembly.
Control and Operation
The speed of the fuel pump is varied under closed
loop control so as to deliver the required fuel rail
injection pressure in accordance with factors such
as driver demand, manifold pressure and
temperature changes. The control loop sensors,
providing feedback information to the powertrain
control module (PCM), are the engine fuel
temperature (EFT) sensor and the injection
pressure (IP) sensor which are both mounted
directly on the engine fuel rail (see
S-TYPE Powertrain Technical Guide). The IP sensor
also has a vacuum feed from the intake manifold
so as to measure the pressure differential.
The required fuel flow is determined by the PCM
and sent to the rear electronic control module
(RECM) which is the power driver for the fuel
pump. The PCM demand to the RECM is a pulse
width modulated (PWM) signal over a single line
at a frequency of approximately 256 Hz and a
duty cycle of 0-50%. The RECM effecively
amplifies this signal by increasing the frequency
by 64 and doubling the duty cycle, thus providing
the necessary high current drive for the fuel
pump. The fuel pump relay, located in the rear
power distribution box, is energised by the PCM
relay and provides a dedicated fused supply to the
RECM for the pump drive.
When the ignition switch is turned from OFF to
RUN or START, the PCM primes the system by
running the pump for 1 second at full speed. The
pump is switched off 1 second after the engine is
stopped. During hot starts, fuel pressure is
increased to prevent vapour lock.
Fuel pump drive status is monitored by the RECM
and communicated to the PCM via the SCP
network.
Outputs from the fuel senders are connected by
independent wires to the RECM which sends the
data to the instrument pack and the PCM.
Inertia Switch
The inertia switch is located behind the trim on
the left side of the vehicle, forward of the front
door post and below the fascia. A finger access
hole in the trim allows the switch to be reset.
