Grand Cherokee 2WD L6-4.0L VIN S (1997)
Fuel Pressure Regulator: Description and Operation
FUEL FILTER/FUEL PRESSURE REGULATOR
Fig. 1 Fuel Tank/Pump Module (Top View)
A combination fuel filter and fuel pressure regulator is used on all engines. It is located on the top of fuel pump module (Fig. 1). A separate frame
mounted fuel filter is not used with any engine.
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 is also part of the assembly.
Fig. 3 Fuel Filter/Pressure Regulator
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 psi, an internal diaphragm closes and excess fuel is routed back into the tank
through the pressure regulator. A separate fuel return line is not used.
