Fuel Pump: Description and Operation
Fuel Pump ModuleThe fuel pump is an integral component of an in-tank fuel pump module. The fuel pump module mounts in a rubber holder attached to the bottom of the fuel tank on brackets. The fuel pump module and the rubber holder are indexed to ensure correct alignment in the tank.
Fuel is drawn from the fuel tank through a 70 micron filter at the base of the module, then through a 400 micron filter at the pump inlet. The pump delivers the fuel to the fuel rail through a renewable in-line filter mounted to the underbody. Unused fuel is returned to the fuel pump module where it passes through another 70 micron filter. A small portion of the pressurized fuel flows through a venturi "teed" into the supply side inside the module. This flow enables a "jet pump to pick up fuel so that the module remains full at all times.
Both the outlet and return ports through the pump module have check valves. The outlet check valve reduces back flow from the fuel rail when the pump is off. The return check valve holds fuel pressure in the return line from the fuel rail and prevents siphoning if a fuel line is disconnected.
CAUTION: The inlet filter must not be folded or damaged and must be squarely mounted on its neck. If the filter is damaged in any way, the fuel pump module must be replaced.
Fuel Pump Control
The electrically powered fuel pump is controlled by the ECM via the fuel pump relay After the ignition is turned on (position 11), the pump runs for about 1 second to build fuel pressure for starting. When the ECM receives an engine speed signal from the crankshaft position sensor, it activates the fuel pump relay, which in turn switches on the fuel pump. The fuel pump will continue to run either until the ignition is turned off or until approximately 1 second after there is no speed signal. The ECM monitors the output to the fuel pump relay for on-board diagnostics.
NOTE: In the event of a vehicle collision, the inertia switch will switch off all ignition powered circuits, including the EMS main relay. This action will remove power from the ECM and cause the fuel pump relay to de-energize, switching off the fuel pump.
Fuel Pump Module:
Fuel Pump Control Chart:
