I noticed the problem the other day when I got out of work. I looked down at my gas gauge and noticed it was at the full mark. Then I started to think about it and I haven't put in any gas for about four or five days. As I'm looking at the gauge it starts to rise even more, to way beyond the full mark. It stayed there for most of the ride home till I got off the highway, then it went to about 3/4 tank. This still seemed like it was more gas than I had. It kept bouncing between the 3/4 mark to the full mark.

The next morning I decided to check the gauge. I first disconnected the sender unit wire at the back of the car and the gauge went all the way past full. Then I grounded the gauge wire and it went to E. So I think this means the gauge is working properly. I didn't have my jack at my house so I couldn't get too far under the car to look for a ground wire. I couldn't see one that was easily visible. I did put in ten dollars of gas today and the gauge did move up a little and it seems to be staying at about 3/4 tank. The gauge is still fluctuating when I take corners like it always has. I'm hoping its just a loose ground and not the sending unit. I don't feel like dropping the tank. Its starting to get pretty cold outside these days. Does anyone know where the ground wire is located. I got my jack back now so I will be able to investigate more in the morning.

Car is 87 chevy caprice 305

Thanks for any help or ideas.

ground is at the tank where your gauge plug is .
try a jumper wire from tank lip to good ground .
one of them alligator type or a big set thrown in the trunk grounded
and hanging out rear to tank .

Thanks for the reply

I was thinking about putting a good ground to the lip of the tank to see what happens. Could a bad ground cause the gauge to be reading incorrectly or does that mean the sender is going bad?

It is not unusual for the grounds to rot off in those harnesses. It is usually just attached to a bolt going into the frame. If you look at the harness leading away from the tank you should be able to track it down. You could try a ground for the frame to the tank to prove it is the problem and if it is the only proper repair is to fix the harness connection. You may also want to check the plugs that go to the tank, they are known to corrode

I got my jack back the other day so I got a chance to go under the car to check it out. I get towards the front of the tank and see exactly what I wanted to see. The ground wire had rotted right off the body. So just made a new ground and gauge is working perfect again. I'm glad thats all it was, It was freezing out and I wasn't in the mood to drop a tank. I could barely feel my fingers after the 5 minutes it took for me to make a new ground lol.

Thanks for the help guys

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