Wrangler 4WD L4-150 2.5L VIN P MFI (1998)
Fuel Pressure Regulator: Description and Operation
FUEL FILTER/FUEL PRESSURE REGULATOR
Fig. 1 Fuel Tank/Fuel 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 338 kPa (49 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/Fuel 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 fuel pump module contains a check valve to maintain some fuel pressure when the engine is not operating. This will help to start the engine.
If fuel pressure at the pressure regulator exceeds approximately 49 psi, an internal diaphragm closes and excess fuel pressure is routed back into the
tank through the pressure regulator. A separate fuel return line is not used with any engine.
