Fuel Pump: Description and Operation
FUEL PUMP MODULEFig. 1 - Fuel Pump Module/Fuel Tank (Top View):
Fig. 2 - Fuel Pump Module Components (Typical Pump Module Shown):
The fuel pump module on all models/all engines is installed in the top of the fuel tank (Fig. 1). The fuel pump module contains the following components (Fig. 2):
- A combination fuel filter/fuel pressure regulator
- Electric fuel pump
- Fuel pump reservoir
- A separate in-tank fuel filter (at bottom of module)
- Fuel gauge sending unit (fuel level sensor)
- Fuel supply line connection at filter/regulator
- A metal lockring to retain pump module to fuel tank
- A gasket between tank flange and module The fuel gauge sending unit (fuel level sensor), and pick-up filter (at bottom of module) may be serviced separately. If the electrical fuel pump requires service, the entire fuel pump module must be replaced.
Refer to Fuel Pump, Fuel Filter/Fuel Pressure Regulator and Fuel Gauge Sending Unit.
FUEL PUMP
The fuel pump is located inside of the fuel pump module. 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.
Check Valve Operation: The pump outlet 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 A 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. Refer to the Fuel Pressure Leak Down Test for more information.