Fuel Pressure Regulator: Operation

WARNING: This page is about a different car, the 2005 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.

The fuel pressure regulator is a mechanical device that is not controlled by engine vacuum or the Powertrain Control Module (PCM).

JTEC Powertrain Control Module: 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 if equipped with a JTEC powertrain control module. NGC powertrain control module: The regulator is calibrated to maintain fuel system operating pressure of approximately 400 kPa +/- 34 kPa (58 psi +/- 2 psi) at the fuel injectors if equipped with an NGC powertrain control module. The regulator contains a diaphragm, calibrated springs and a fuel return valve.

Fuel Flow: Fuel migrates into the fuel pump module reservoir through a one-way check valve located on the bottom of the module. This check valve prevents the reservoir from running empty such as when going up or down hills with a low amount of fuel in the tank. If fuel pressure at the pressure regulator exceeds approximately 49 psi (JTEC module) or 58psi (NGC module), an internal diaphragm within the regulator closes, and excess fuel is routed through a second fitting on the main fuel filter, and back into the fuel tank (the fuel pressure regulator is installed into the return side of the system). Pressure regulated fuel is then delivered from the third fitting on the fuel filter, up to and through the fuel rail, and on to the fuel injectors.

The fuel pressure regulator also 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 of the fuel pump module housing.

A separate fuel return line from the engine is not used with this system.