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BC

BC 12/7/2017

2004 Ford F-150 XLT 8 Cyl 5.40L

Engine

The fuel pump has stopped working as well as the radio. All at the same time.

Could the fuse panel need replacing like I've been told and if so how do I check to see if that's really the issue. Thanks

1 Answer


HouseCallAuto

HouseCallAuto 12/7/2017

I do not see an obvious common cause that would knock out fuel and radio from the same cause but...cars can do crazy things sometimes no I will not say its not possible to have a related cause. I would just diagnose the cause of no fuel pump function first.

1. Connect a Digital Volt-Ohm Meter (DVOM) to the Pink/Black (PK/BK) and Brown/White (BN/WH) wires at the fuel pump leaving it connected.

2. Monitor the voltage across the wires looking for at least 5-8 V. If the voltage is present but there is no fuel pressure, verify the fuel level in the tank and that there are no obstructions to the fuel pump inlet in the tank. Before replacing the fuel pump, disconnect the fuel pump driver module and jump battery voltage to the PK/BK wire and ground to the BN/WH wire, and recheck fuel pressure. If there is still no fuel pressure and no problems in the fuel tank, replace the fuel pump as needed.

3. If there is no or low voltage across the wires to the fuel pump when cranking, verify the White (WH) wire at the fuel pump driver module (located above the spare tire on the cross member) maintains battery voltage and that the Black/Yellow (BK/YE) wire is a good ground. Also try jumping the WH wire to the PK/BK and the BK/YE to the BN/WH. This should run the fuel pump at full battery voltage producing at least 75 PSI of fuel pressure. If the voltage is low under load, start with checking for a problem at connector C3138 (12 terminal connector under the driver's door area at the frame rail). If all OK, inspect the fuel pump driver module for any corrosion or damage and replace as needed.

4. If the fuel pump driver module physically looks OK and the power and ground to it are OK but there is no voltage across the fuel pump wires while cranking the engine, monitor the command to the module on the White/Yellow (WH/YE) wire. This will be a duty cycle reading that will read 75% with key on when the Powertrain Control Module (PCM) is not commanding the fuel pump to run and be between 5-50% while cranking the engine. The higher the duty cycle reading, the higher the voltage should be across the fuel pump wires. If the duty cycle is present, the power and ground are present, but the fuel pump driver module will not run the fuel pump, suspect a bad fuel pump driver module.

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