There are two wires that connect to the sending unit on most 80's Fords.
One sends a ground signal to the fuel gauge. The other is for a low fuel light.
I'm not sure which is which. You'd have to check with a wiring diagram. I'll search around some more, and see if I find anything.
Once you do know which wire leads to the gauge, remove the connector at the sending unit, and jump that wire to a known good ground. Do this with the key Off.
Then get in, turn the key On, and watch the gauge. With that wire grounded it should move to Full in a nice even sweep. If it does it means the gauge is working properly.
If it does in fact move to Full then check the connection at the tank. A loose/corroded connection will cause the complaint.
If you are confidant the connection is good, and the gauge moves to Full when that wire is grounded, then the sending unit is defective.
Other things to check is a kinked, or blocked fuel filler hose, (the big one). And, that any vapor recovery lines/vents are clear. Air has to come out of the tank for gas to go in. Your tank is probably full when it kicks the pump off, but sense you're in there might as well check.
Make sure to use a brass bar, or punch, to remove, and install the sending unit retaining ring. Don't want any sparks. And renew the pick up tube sock (screen), and the O-ring with the new sending unit. Use some dielectric grease on the connection. Replace the fuel filter.
Hope this is of some help. Feel free to ask any more questions, and let me know how things are going.
1995 Thunderbird LX 4.6l 97 Headlamps/Hood All Red Tails Muffler/Resonator Delete
2004 Tahoe 5.3 4x4
2008 Acadia Limited AWD
...still looking for a clean, low mileage, rust free 96/97 Thunderbird 4.6
Last edited by rushtonracing; 10-12-2014 at 07:34 AM.