Precision fuel pump

[DConley]

I am working on a friend's 2004 Expedition 4.6L engine. He was having driveability issues and parked it a few years ago. My first diagnosis was no fuel pressure, checked for power and ground at the pump, which was good so I got a Precision brand pump and put it in. Started right up but still had driveability issue, no power when trying to drive. I went back a few weeks later to do some more diagnostics and again no start, no fuel pressure. O'Reilly waranteed the pump so I put in the second new one. Again, stated right up. I had 30 psi with key on, 60 running. I let it run for about an hour. Still had no power while driving so I went back today (about two weeks later) and NO START, NO FUEL PRESSURE. I didn't have my electrical test equipment with me but I did check the connector which was tight and fuse, which was visibly not blown.
Are these pumps prone to such quick failure? I also thought the fuel pressure regulator was part of the pump but I watched a You Tube video (different engine) that showed one in the fuel rail behind the throttle body. Does the 4.6 have this? I also watched another video of a guy who also had two Precision pumps go bad. Any comments or suggestions?

 

[AWAR]

I added an external relay to my 04. You might look at the post in the gen 2 electrical section. I was having random shutdown issues.

 

[Hamfisted]

No, these fuel pumps are not subject to failing like that. Check the PCM relay in the fuse box there at the passenger kick panel. ( Top right relay is the PCM relay ....) . Look for melted plastic on the socket and around the terminals of the relay. That indicates severe heat between the PCM relay and the fuel pump relay. If you find heat damage you can swap the PCM relay with one of the other two up there just to test the circuit and see if you get the fuel pump to come alive. In the end you have to either replace the fuse box, or if you want to deal with the soldering, replace the fuel pump relay itself. The fuse boxes are very year model and date of production unique. You can't just go to a salvage yard and grab one just because it looks the same.


IF you want to attempt the external relay installation trick, these are the relay connection points for the standard 5 pin relay for the fuel pump in the middle of the fuse box circuit board.







5 pin Relays & Pigtails on Amazon







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