RAM 1500 Truck 4WD V8-5.9L VIN Z (2002)
Fuel Pressure Regulator: Description and Operation
Fig. 3 Side View - Filter/Regulator
FUEL FILTER/PRESSURE REGULATOR
A combination fuel filter and fuel pressure regulator (Fig. 3) is used on all engines. It is located on the top of the fuel pump module. A separate
frame mounted fuel filter is not used with any engine.
Both fuel filters (at bottom of fuel pump module and within fuel pressure regulator) are designed for extended service. They do not require normal
scheduled maintenance. Filters should only be replaced if a diagnostic procedure indicates to do so.
Fuel Pressure Regulator Operation: The pressure regulator is a mechanical device that is not controlled by engine vacuum or the powertrain
control module (PCM).
The regulator is calibrated to maintain fuel system operating pressure of approximately 339 kPa ± 34 kPa (49.2 psi ± 5 psi) at the fuel injectors. It
contains a diaphragm, calibrated springs and a fuel return valve. The internal fuel filter (Fig. 3) is also part of the assembly
Fuel is supplied to the filter/regulator by the electric fuel pump through an opening tube at the bottom of filter/regulator (Fig. 3).
The regulator acts as a check valve to maintain some fuel pressure when the engine is not operating. This will help to start the engine. A second
check valve is located at the outlet end of the electric fuel pump. Refer to Fuel Pump-Description and Operation for more information. Also refer
to the Fuel Pressure Leak Down Test and the Fuel Pump Pressure Tests.
If fuel pressure at the pressure regulator exceeds approximately 49.2 psi, an internal diaphragm opens and excess fuel pressure is routed back into
the tank through the bottom of pressure regulator.
Both fuel filters (at bottom of fuel pump module and within fuel pressure regulator) are designed for extended service. They do not require normal
scheduled maintenance. Filters should only be replaced if a diagnostic procedure indicates to do so.
