Fuel Pump Module (Liberty)
The electric fuel pump is located inside of the fuel pump module. The fuel pump module assembly is located in the fuel tank. See Figure . The assembly is divided into 2 sections: an upper and a lower section. See Figure andFig 1 . The lower section is locked to the bottom of the fuel tank. The complete assembly contains the following components:
- A fuel pressure regulator.
- A separate fuel pick-up, or inlet filter.
- An electric fuel pump.
- A lockring to retain upper section of pump module to tank.
- A rollover valve.
- A vent fitting for On-Board Refueling Vapor Recovery (ORVR) system.
- A soft gasket between tank flange and module.
- A fuel gauge sending unit (fuel level sensor).
- Two fuel line connections (supply and return).
A 12 volt, permanent magnet, electric motor powers the fuel pump. Voltage to operate the electric pump is supplied through the fuel pump relay. Fuel is drawn in through a filter at the bottom of the module and pushed through the electric motor gearset to the pump outlet. The bottom section of the fuel pump module contains a one-way check valve to prevent fuel flow back into the tank and to maintain fuel supply line pressure (engine warm) when pump is not operational. It is also used to keep the fuel supply line full of gasoline when pump is not operational. After the vehicle has cooled down, fuel pressure may drop to 0 psi (cold fluid contracts), but liquid gasoline will remain in fuel supply line between the check valve and fuel injectors. Fuel pressure that has dropped to 0 psi on a cooled down vehicle (engine off) is a normal condition.
The fuel gauge sending unit (fuel level sensor) may be serviced separately. If the electrical fuel pump, primary inlet filter or fuel pressure regulator require service, the lower section of the fuel pump module must be replaced.