I am need of some help. I have a 67 Firebird and the other morning I started the car and the fuel guage went past the full mark and has settled half way over past the Full mark and will not move. I unplugged the battery to see if this might help but it did not. Does anyone have any ideas what I can do to fix this problem. Is this a gas tank problem, electrical problem. Please Help.

Sounds like a bad ground problem. If it was working fine before, there is a ground strap from the sender unit under the car at the back of the tank attached to the body. Make sure it is attached and clean(no rust). It's just one wire and the only thing near the tank.

If it needs cleaning does it require draing the gas in the fuel tank ?

No, it's just a wire that comes off the top of the tank from the sending unit. If you crawl under the car you'll see it. It's held to the frame by a screw, remove it make sure it's rust free clean the contact areas with some type of abrasive brush or paper and reattach.

I had the same problem.

It was not the ground wire, it was the strap that goes from the pin to the actual sending unit rheostat on the inside of the tank.

The strap was loose on the pin and not making contact.

I soldered the pin to the strap and reassembled.

Of course, check the ground wire first, but if that is fine, drain and pull the tank and the sending unit out, and repair or replace it.

My gauge has been pitching fits recently. Goes to full for a while. Returns to where it is supposed to be for a while, back and forth. I suspect a bad ground, but I thought I had taken great care to make sure I would not have the problem I am currently having.

Good luck on you repair!