Liberty Sport 2WD L4-2.4L VIN 1 (2002)
Fuel Pressure Regulator: Description and Operation
The fuel pressure regulator is located on the bottom of the upper section of the fuel pump module. The fuel filter is not combined into the pressure
regulator on this model.
The fuel 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 main fuel filter is not combined within the fuel pressure regulator as in other Jeep models. Three different fuel filters are used: 1. a serviceable,
separate, externally mounted, main fuel filter; 2. a non-serviceable primary filter located on the bottom of the electric fuel pump; 3. a non-serviceable
secondary filter attached to the side of the fuel pump module.
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. A primary fuel filter (sock) is
located at the bottom of the electric fuel pump. Fuel is drawn in through this filter, and up to the electric fuel pump. High pressure fuel (unregulated) is
supplied from the electric fuel pump through a high-pressure line to one of 3 fittings on the main fuel filter. If fuel pressure at the pressure regulator
exceeds approximately 49 psi, 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.
A secondary fuel filter is attached to the side of the fuel pump module. High-pressure from the electric fuel pump causes a siphoning action across a
passage connected to this filter, and fuel is drawn into the fuel pump module reservoir. This is used to help keep the module reservoir full of fuel.
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. 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.
A separate fuel return line from the engine is not used with this system.
