Whenever I fill up the tank in my '85 f-150 it only reads 1/2 full. As soon as it gets filled, it will read right, but very shortly after it drops to 1/2. Anything I can do to remedy this? I've got a 3000K mile trip comming up, and I'd rather the fuel gauge work right

 

The fuel tank sending unit probably needs replacing. They're basically just mechanical rheostats and the very fine wire breaks and unravels. I'd suggest going to rockauto.com and getting one from there, I've had really good experiences with them.

-ct

 

I'm having the same problem with my '80. It is reading empty now no matter how much fuel is in the tank. On a warm day it may read correctly or at least indicate that some fuel is in the tank. I'm thinking that the problem may be with the printed circuit board on the back of the instrument cluster. Don't know if my trouble shooting is correct but given the fact that my inst. lights work when they want, I think it is logical. Hopefully someone will post with some better insight. Keep us posted on what you find out, can use all the help I can get.

Gil

 

If you want to test the gauge and the wiring, go back to the tank and take the sending unit wire off. With the key in run, but the engine off, ground the wire. The fuel gauge will peg in one direction. Then take the wire off ground and let it hang in the air. The gauge should slowly move over and peg in the opposite direction. If it passes this test, the gauge and the wiring back to the tank are good, and the sending unit is bad.

 

I'll have to give it that test tomorrow, and see what I got. Do I have to drop the tank to take the sending unit off? I believe its a side mount

 

I had the same problem and I pryed the sending unit apart and played with the windings and the little metal button and fixed it. They tend to fatigue over time causing a bad connection

 

Yes, most definitely.

-ct

 

gdgerland. If your gauges fluctuate and the panel lights flicker then there is a pretty good chance the ground connection where the wiring harness connector plugs into the printed wiring is dirty or not seated fully. There is only one ground circuit between the instrument cluster and the harness. I found that adding another wire from the instrument voltage regulator mounting screw directly to the dashboard metal frame cures the problem.

 

Sorry, didn't mean to be a highjacker, just thought we might have a common problem. Thanks, Ken, I will check the ground and add an additional one like you suggested. I also would have to drop my tank to check the sending unit so I will wait until I remove the bed for floor replacement to check that out.

Gil

 

Is this for dual tank trucks also? I have heard numerous times that it could be an issue with the switch as well, just checking with everybody here before I do this. My 85 dual tank f-150 has a no fuel level indication as well. I know this method works, I did this on my Z28 a few years ago and it turned out to be the sender.

Cheers!!

 

Yes, this test will work for dual tanks. Just make sure you have the switch in the correct position for the tank you are testing.

I had trouble with my dash switch, and I used to flip it up and down very quickly several times, and it would start working. But after awhile, that didn't work and it needed a new switch.