Range Rover P38
19
FUEL SYSTEM
NEW RANGE ROVER
28
DESCRIPTION AND OPERATION
Ignition Relay:
The ignition relay supplies the power feed to the coils
(6.5 amps), purge valve (1 amp, non-continuous) and
heating elements of the HO
2
S sensors (8 amps,
non-continuous). The relay is ignition key controlled,
when the key is turned off, supply to the coils is
immediately cut. Failure of this relay will result in no
ignition.
Ignition switch sense:
This is used to initiate the power up and power down
routines within GEMS. The input is supplied from the
ignition relay. When the ignition is turned on, the
ignition relay is energised and the GEMS ECM starts
its power up routines and turns on the ECM main
relay, the main power to GEMS and its associated
system components. When the ignition is turned off,
GEMS will usually maintain its powered up state for
several seconds (up to 20 minutes in extreme cases
when cooling fans are required) while it initiates its
power down routine. On completion of the power
down routine, the ECM main relay is turned off.
Fuel Pump Relay:
The fuel pump relay is fed from the ignition relay and
controlled by the ECM. The relay is activated in
ignition key position 2 to prime the fuel system for a
period of time controlled by the ECM. Failure of this
relay will result in no fuel pressure.
Advanced Evaporative Emissions System - 98MY
to 99MY (NAS only)
The Advanced evaporative emissions system is
included on NAS vehicles from 98MY in compliance
with OBD strategies. The system has the capability of
detecting holes in the fuel system down to 1 mm (0.04
in.). The leak tests are performed by the ECM,
allowing the tank to be depressurised and measuring
the pressure over a period of time.
See EMISSION CONTROL, Description and
operation.
Fault codes:
•
P1440 - Purge valve stuck open.
•
P0442 - Evaporative loss control system - small
leak
•
P0448 - Evaporative loss control system - major
leak
•
P0496 - Evaporative loss control system - major
leak
•
P0446 - Purge canister closure valve information
•
P1447 - Purge canister closure valve - poor
performance
Fuel Tank Pressure Sensor
This sensor is used on NAS vehicles with advanced
evaporative emissions systems. The sensor is located
in the fuel tank sender unit and is not a serviceable
item. The GEMS ECM checks for any fuel system
leaks through joints and holes, by measuring the
pressure drop after the vent seal valve is shut. The
diagnostic system performs out of range and validity
checks.
The following failure modes are possible:
•
Connector or harness open circuit
•
Sensor earthing problem
•
Blocked sensor