Q: How to remove and replace a fuel pump in a Lincoln Navigator?
A: Siphon residual fuel from the tank before removing the fuel pump. Disconnect the negative battery cable, raise the vehicle, and remove the Fuel Tank. Highlight alignment marks on the fuel pump assembly and tank. Remove fuel pump assembly bolts and pull the assembly from the tank. Discard the old seal ring. If reusing the pump, clean the strainer in solvent. If installing a new pump, it'll come with a new strainer. Disconnect the electrical connector and remove the pump from the assembly. Clean the pump mounting flange and tank surface. Install in reverse order, using heavy grease to keep the new seal in place.
Q: How to perform a fuel pressure and Fuel Pump test on Lincoln Navigator?
A: To perform a fuel pressure test, you need a fuel pressure gauge and adapter set. After relieving fuel pressure, disassemble any fuel connection with a shop towel laid over it. Remove the fuel filler cap and listen for a whirring sound when the ignition key is turned on. If there's no sound, check the fuel pump fuse and test for battery voltage to the fuel pump relay and PCM relay connectors. If there's no voltage, inspect the fuse(s) and wiring circuit. If voltage is present, check for battery voltage at the fuel pump harness connector. To check operating pressure, connect a fuel pressure gauge to the fuel pressure test port and start the engine. If the pressure is low, test the fuel pump or pressure regulator. If it's high, check for blockage. Use a vacuum pump to test the fuel pressure regulator. For returnless fuel systems, tee into the fuel pressure gauge between the fuel delivery hose and fuel rail. If the pressure is off, inspect the fuel delivery lines, hoses, and connections. Replace the fuel filter and recheck the pressure. If all else is okay, inspect the fuel pump inlet strainer and replace the fuel pump if needed. After testing, reconnect the fuel delivery line.