Fuel Pump: Description and Operation

Fuel Delivery
A recirculating fuel system provides a continuous supply of pressurized, cooled fuel to the fuel rail. There is sufficient fuel flow to allow full load engine operation at all times.

Fuel Pump
Fuel is drawn from the fuel tank by an electric pump located on the rear subframe and is delivered to the fuel rail through a renewable filter mounted to the underbody. Unused fuel is returned to the tank swirl chamber where it passes through a venturi before mixing with the remaining fuel in the tank. This action cools the returning fuel.

The in-line fuel pump is a roller type pump driven by a permanent magnet electric motor. An eccentric rotor mounted on the armature shaft has metal rollers housed in pockets around the circumference When the motor is energized, centrifugal force acting on the rollers forces them outward so that they act as seals. The fuel between the rollers is then forced to the outlet side of the pump. A replaceable non-return valve is threaded into the pump outlet. The non-return valve prevents fuel pressure loss when the pump is not running.

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:

Fuel Pump Control Chart: