Crazy Fuel Gauge Problem

[joefiero]

My fuel gauge moves erratically while the engine is running. Also the volt guage reads 8 volts when the key is turned to the on position before the engine is cranked. After it is cranked the volt gauge moves to 13.5 volts but after it warms up it drops to 11 volts. The alternator is putting out correct volts i checked it with a handheld voltmeter at the battery post reads 14-15 volts plus i had it checked at autozone, advanced auto and oriley's. I've replaced all my grounds at the engine compartment plus added an extra 4 gauge ground from the block to the chassi. All ground connections and surfaces are shiny clean and have deox on them. Two more grounds to the chassi have been found and cleaned, one under the center console in front of the ecm and the other behind and slightly above the radio. Instrument panels were also pulled out inspected and cleaned plus i checked the ground terminals at the PIN plug in harness with an ohms meter 0.0 to chassi. Well to be safe i added an extra ground wire at each PIN. From the ground at the harness to the chassi. With all that i have checked and done still no improvement on the erratic fuel gauge and lazy volt gauge. Is there anyone out the that might have an answer for me. I would greatly appreciate it. 86 FIERO GT 2.8 LITER STANDARD 4 SPEED 275,000 MILES.

[joefiero]

I've had no replys to this yet but i believe my problem is at the sendor unit in the fuel tank. The car sat for 2 years near empty, thus the sendor may have some rust builup. I come to this conclusion after i filled the tank. Now the gage is actually operating better, i think the sendor is stating to free up and work properly again. Not quite so crazy anymore. Plus when i filled it up i put a bottle of STP fuel injector cleaner in that may be helping free it up.

[Old Lar]

Fiero gas guages are notoriously inaccurate. I just reset my trip odometer at every fillup then get gas at 200 mile intervals.