Fuel Gauge is acting up. Occasionally it works, but most of the time it is pegged high to the right side above the Full mark.

Any ideas what is wrong and how to correct the problem?

Thanks for the hlep

If it works sometimes but not others, it could be a problem with the sending unit in the tank. HERE is a thread on how to test and repair the issue.

The way the fuel gauge works is that when the resistance from the sender is zero ohms, the gauge reads "EMPTY" and when the resistance is 90 ohms, the gauge reads "FULL". Since your gauge reads beyond full, that means either the wire from the sender is broken or the rheostat in the sender is broken (either case will result in infinite ohms, pegging the gauge). To test which one is the most likely you need a mulitmeter set to ohms (200 ohm range or so), disconnect the yellow 3-wire connector near the middle of the firewall in the engine bay that leads to the fuel tank, and on the half going to the fuel tank place one meter lead on the pin with the pink wire and the other on the black wire. If you get more than say 120 ohms, your sender is faulty

If you get between zero and 90 ohms, then your sender is OK but the wiring on the chassis half of the connector is problematic. If that's the case, you can figure out which wire is faulty by placing one meter lead on the pin with the black wire of the other connector half (the half of the harness that goes back to the instrument panel) and the other meter lead on a known good ground, like one of the three top strut nuts. You should get very close to zero ohms if that wire is good, and infinite ohms if it's broken.

Testing the pink wire for continuity is a bit more challenging so if you get this far post the results and I or someone else can walk you through how to test that wire.

quote Originally posted by seajai: If it works sometimes but not others, it could be a problem with the sending unit in the tank. HERE is a thread on how to test and repair the issue.

I have an 87 Fiero GT with stock motor and when I bought my car the fuel gauge didn't work. I bought both factory fuel gauge and new sending unit from Fiero Store. Gas gauge works when you fill the tank the needle goes just a hair under full mark, but as you start driving and using fuel the gas gauge will intermittently peg and keep it up until you're a half tank or less and then reads normal. I had this installed at a GM dealership too so not sure why a new sending unit would do this and only in the 3/4-1/3rd tank range? Any ideas?

This is very helpful and I am super excited to have some ideas as to where to begin! I have the whole weekend to try and get this figured out and then once the rest of interior is put back in I will be ready to take it for for my first ever spin down the road!
I will check back to give an update as to how it goes.
Thank you for your help.
Pat