RAM 3500 Van V8-5.2L CNG VIN T (1996)
Fuel Pump Relay: Description and Operation
CNG
Power Distribution Center
DESCRIPTION
This relay is used in place of the conventional fuel pump relay It is used to electrically control operation of the high-pressure fuel shut-off solenoid
within the fuel pressure regulator.
The powertrain control module (PCM) operates both the high-pressure fuel shut-off solenoid relay and the automatic shut-down (ASD) relay
through one common ground path (also refer to Automatic Shut-Down (ASD) Relay). The PCM operates the relays by switching the ground path
on and off (both relays turn on and off at the same time).
OPERATION
The PCM turns the ground path off when the ignition switch is in the Off position. Both relays (ASD and high-pressure fuel shut-off solenoid) are
off. When the ignition switch is in the On or Crank position, the PCM monitors the crankshaft position sensor and camshaft position sensor signals
to determine engine speed and ignition timing (coil dwell). If the PCM does not receive the necessary crankshaft position sensor and camshaft
position sensor signals when the ignition switch is in the Run position (indicating the engine has not started and is not running), it will de-energize
both relays. When the relays are de-energized, battery voltage is not supplied to the fuel injectors, ignition coil, CNG high or low-pressure fuel
shut-off solenoids and oxygen sensor (O2S) heating element.
LOCATION
The high-pressure fuel shut-off solenoid relay is located in the Power Distribution Center (PDC). The PDC is located in the engine compartment.
