fuel gauge problems
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Joined: Feb 2006
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fuel gauge problems
Ok, i got a 77 f100 and my fuel gauge goes straight to full with the tank empty. I replaced the fuel sending unit and checked the gound to be sure that is not the culprit but still, the gauage goes to full. What's up? Help
Moderator
Joined: Jan 2001
Posts: 56,947
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From: Virginia
Take the wire off the sending unit at the tank, and ground it. Then take the sending unit wire and let it hang in the air. With the key in run, and someone watching the gauge, everytime you do this with the wire at the sending unit, the fuel gauge should swing slowly back and forth. If it passes this test, there is still something wrong with the sending unit.
I am thinking your guage reads full with 0 resistance(wire grounded) and high resistance(wire hanging in the air) is empty. If this is the case, this points to your sending unit wire touching ground somewhere along the way from the instrument cluster to the fuel tank if your guage reads full all the time.
I am thinking your guage reads full with 0 resistance(wire grounded) and high resistance(wire hanging in the air) is empty. If this is the case, this points to your sending unit wire touching ground somewhere along the way from the instrument cluster to the fuel tank if your guage reads full all the time.
Postmaster
Joined: Apr 2000
Posts: 2,838
Likes: 6
From: SD
If it reads full, most likely a grounded wire. If it reads empty, most likely a broken wire or bad connection. Look over the wiring under the pickup for cracked broken wires. I usually replace the wires along the frame, be sure to solder all splices and clean/dielectric grease all grounds and connectors. If this still doesn't work after the wires are repaired, do Franklin's test. IF that passes, but the guage still doesn't work, then test the sending unit.
Marty
Marty
