Fuel pump grounding through tail lights
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Fuel pump grounding through tail lights
I have an 04 f250 5.4 4x4. Auto trans. It would appear the fuel pump is grounding somehow through the tail lamps. Truck will start and run like a top until the brake pedal is depressed or the lights are turned on. Or the reverse lights come on. While it's running the rear parking lights and cab clearance lights are illuminated very dim. Also the lights illuminate only for the fuel pump prime sequence koeo. I'm thinking bad fuel pump ground stealing the tail lights ckt ground until the lights are turned on and the ckt is overloaded causing the pump to stop and the engine stalls. Has anyone else run into this or have a good point to start. Thanks in advance.
Elder User
Joined: Dec 2004
Posts: 819
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From: Putnam Valley, New York
Grounding
The fuel pump and MOST OF THE REAR LIGHTS are grounded through the ground point known as G400. G400 is located on the left side frame rail in the vicinity of the fuel tank. If that ground does not make good contact, it will probably make the truck do what you are describing. Unbolt it, clean it, and reconnect it---Hopefully your problem will disappear. Let us know how you make out.
RON
RON
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Ron do you happen to know if g400 is on the frame behind the fuel tank? Oddly enough I am not seeing any frame or body grounds from the end of the cab rearwards. The pump is definetely using the tail lamps as a ground. If I unplug both rear bulbs the pump stops and the engine stalls. If I leave one or the other plugged in it will stay running.
Elder User
Joined: Dec 2004
Posts: 819
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From: Putnam Valley, New York
G400
According to my (2003) EVTM, G400 is on the inside of the left frame rail somewhere in the area of the fuel tank. Maybe 2004 is different, but I doubt it. It is possible that it is located on a crossmember instead of the rail on an 04, but I would think 99-04 were all similar. Unbolt the one on the crossmember, clean it and reinstall it---Hopefully, that will fix your problem.
RON
RON
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Fixed
G400 on an 04 f250 is located in between the x crossmember that holds the spare tire. I dropped the spare and there it was poking out of the harness. It was broken at the frame terminal. I cleaned and reattached it and it fixed all of the problems. Thank you for your help Ron.
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