Gremlins in the Gauges

sounds to me like there is a dead spot on the little resistance film in your fuel level sender, depending on how difficult it is to get to and how expensive it is, you may want to just replace it, or else pull it and slap a multimeter on it and see if the resistance changes smoothly as you move the float through its full range. I am pretty sure you will find that this is your problem.

good luck,

nate

I had something similar happen to my old Chev Celebrity. After only being able to afford 1/2 tank of gas at a time, I filled it up one day and the gauge would go back and forth from full to empty at random. It cleared up after a while, I assumed it was just that that area of the gauge sensor hadn't seen contact in a while and had gotten a littly dirty.

Your problem may clear up after a few fillups.

Your problem could also be in the float itself. The float is a small plastic or brass bubble in the tank. They sometimes leak, fill up with gas and then just move around up and down changing what your gauge says. Either way, you need to pull the unit out of the tank to test it.