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HDGENE, Ford Senior Master/Diesel/Trans
Category: Ford
Satisfied Customers: 5564
Experience:  25 years Auto experience, Ford ,GM, Chrysler, Asian & European
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I have a 1994 ford f150 4x4 5.8, I shut the truck down about

Customer Question

I have a 1994 ford f150 4x4 5.8 , I shut the truck down about 3 months ago, trying to fix it. The fuel gauge is pegged out and fuel pump not working, already changed fuel pump and I have check the relay,it's fine, what can go bad and cause both the gauge and pump to stop working
Submitted: 1 year ago.
Category: Ford
Expert:  HDGENE replied 1 year ago.

Hello, if the fuel sender wire is shorted to ground it will cause the fuel gauge to read full. Or an issue with the gauge itself. With the fuel pump unplugged it should read empty, if it remains pegged the sender wire is shorted to ground or its in the instrument cluster itself. Far as the fuel pump circuit, the eec power relay supplies power to the fuel pump relay only for a few seconds when the key is turned to on to prime fuel system. Need to verify the check engine light operation, if it isnt coming on when the key is turned to on, there is either an issue with the eec power relay not supplying power to the circuit and fuel pump relay or blown fuse/fusible link for the power supply to the relays

Customer: replied 1 year ago.
Okay, you have me 2 different conclusions, let me say this again. Both without at the same time,period. What does both the fuel guage and fuelpump have in common or goes thru to feed power or ground. Like I said I check the wires ,current flows thru them or grounded like it suppose to be, the fuse is ok,changed distribur ,computer ,ignition switch ,seems like I very much thinking its in the dash,of yes I change out the cluster from my buddy's truck and swap my parts to his,and no problems with my parts
Expert:  HDGENE replied 1 year ago.

The power supply for the fuelpump is fed from the battery to eec power relay, eec power relay to fuel pump relay. fuelpump relay to inertia switch, inertia switch to the fuel pump. the ground circuit is a body ground for the fuel pump circuit, the yellow wire is the gauge wire for the fuel sender on the fuel pump