Fuel Pump: Description and Operation

The Electronic Fuel Injection (EFI) system uses a fuel tank, and a fuel pump and sender assembly. The fuel tank has an internal pump cavity where the fuel pump and sender assembly rest. This design provides satisfactory operation during extreme vehicle maneuvers and steep vehicle climbing with low-tank fill levels.

The fuel pump is mounted on the fuel gauge sender assembly inside the fuel tank. This assembly includes a check valve located in the outlet of the fuel pump. The function of this valve is to maintain pressure in the function of this valve is to maintain pressure in the system after the vehicle is shut down. The pressure retention helps prevent hot starting problems. This pump is capable of supplying 60 liters of fuel per hour at 310 kPa (45 psi). The fuel pump has an internal pressure relief valve which limits the maximum fuel pump pressure to 850 kPa (125 psi). This only takes effect if there is a system blockage, causing system pressure to rise too high. The system operating pressure is controlled by a pressure regulator on the fuel.

The fuel pump is protected at its inlet by a nylon pickup element. This nylon element filters dirt and contaminants which could plug or damage the internal pump components while at the same time allowing passage of small quantities of water which may accumulate within the fuel tank sump.
The electrical system has a fuel pump control relay controlled by the Electronic Engine Control (EEC) module, which provides power to the fuel pump under various operating conditions. When the ignition switch is in the OFF position, the contacts of the EEC power and fuel pump relays are open.