1988 GT, 3.4L, 4T60.

For over 15 years I've been using my odometer to determine when to refill. Gas gauge was always screwy so I didn't trust it. I'd zero the odometer each time I filled up.

I forgot to zero the odometer the refill before last. Didn't drive the Fiero for long enough to forget I forgot. Tried to fill up based on the old, invalid miles since last fill up. Pump clicked off real quickly as if the tank was full - which it was. But I was too stupid to realize and thought something was wrong with the pump. Tried over and over to get more gas into the car.

Please see image. Whereas before my over-overfilling the gauge would sort of work, needle right on full when full and showing 3/4 full after a hundred miles. If it showed around 1/2 full you'd better find a station soon. The needle has been stuck on hyper-full as shown since the over-overfilling episode no matter how much gas is used.

I did the 1988 fix-gas-gauge-needle-pegging rewiring a long time ago.

Is this mother nature's sign to have the nice people at my favorite garage drop the tank, insert new "sending" unit (float), make connections and hope? Or is the dash gauge itself now worthless? Ideas on what and how to test?

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John W. Tilford

Fuel Gauge/Sending Unit Troubleshooting
http://www.calgaryfieros.co...docs/fuel-gauge.html
IF it doesn't reach F or E, repeat the test on the back of the gauge console panel which the next link:

Faulty fuel gauge or sender? Here�s how with pics
https://www.fiero.nl/forum/...090219-2-086442.html

Find a street with a speed bump, hump, or speed table and hit it above the speed limit. It might shake it loose if it's stuck at the top.

The reason I suggest this is that one of our local guys had one that was stuck. He went to a vacant parking lot and wiggled, wobbled, whipped it side to side, accelerated and braked hard, and it came loose.

[This message has been edited by fierofool (edited 12-10-2025).]

It's not uncommon for the plastic baffle in the fuel tank to warp and interfere with the movement of the float.

It that is the case, tell your favorite mechanic to check the front of the baffle and trim it if needed. The aftermarket sending unit/float assemblies usually require some tweaking of the float rod to work properly, even after trimming the baffle.