When I turn on the car, the fuel gauge goes from E to F. But this is not a true reading. It used to work, and it would get stuck on a 1/4 tank, atleast I knew that it was almost time for a fill up.

What can I do to fix this?

 

Check the ground wire on the sending unit. if it comes undone it will shoot to a full tank reading. I had the same problem and this was the culprit. As for it to stop reading at a quarter tank I have no idea what the cause would be. My guess...maybe the float is getting caught up when it get that low on the slide and stops reading.

 

Have you changed anything on the fuel lines lately, Oldsmobile of that era grounded their gas tanks through the fuel lines if a repair was made and a rubber section installed your ground will be bad .It's always good to clean the ground wire just to make sure you have a good connection They often corrode. If it still doesn't work with a separate wire ground the sender to a known good surface and recheck your results, gauge should be on full now. Also see that the gauge is receiving a full 12 volts or all this is in vane...Tedd

 

the fuel line has been repaired. where is the ground exactly? so i can get it on the lift and check it out.

 

If the ground turns out not to be the problem, you need to check the wiring from the sending unit to the gauge. Pull the connector apart (should be in the rear of the car behind the bumper near the license plate) and ground the side coming from the gauge. Then turn the ignition ON. The gauge should go to E. Remove the wire from ground, and it should go to F or past it. If it does these things, the gauge is ok.

The problem is then likely the sending unit. The gauge not going below 1/4 could be a problem with the gauge itself or a problem with the sending unit. The test above will answer some of this. If the gauge sticks on 1/4 when you ground the wire, then gauge itself needs attention.

But the fact that the gauge now goes all the way to F and stays there means an open circuit, and that's due to a bad ground, an open in the wire from the sending unit to the gauge, or a defective sending unit.


As far as where the ground wire is, I'm not sure on your car, but on my car, it's just forward of the tank, and attaches to the body right there. You need to get under the car so you can see the front side of the tank and look for a black wire that should be attached to the body or frame.

 

x2

 

thanks. i'll check it when i get it up on the lift! hopefully thats all that the problem is.