Fuel Pump: Description and Operation

Fuel Pump In Tank Cut Away:

The fuel pump used is a positive displacement, immersible roller vane pump with a permanent magnet electric motor. Fuel is drawn into the pump through a filter mounted in the tank on the submerged end of the input tube, and pushed through the electric motor to the outlet. The pump contains a pair of check valves. The first check valve relieves internal fuel pump pressure, and regulates maximum pump output, by bleeding off excess pump output pressure back into the fuel tank. The second check valve mounted near the pump outlet line restricts fuel movement in either direction when the pump is not operating. This check valve maintains fuel pressure in the fuel supply line when engine is turned off. Fuel pump voltage is supplied through the Auto Shut Down (ASD) relay. The fuel system is under a constant pressure of approximately 380 kPa (55 psi), even when not operating, and fuel pressure must be released prior to servicing the fuel pump.