I had my mechanic install a used fuel tank, new Fiero store sending unit, and new AC Delco fuel pump about 5 months and 5,000 miles ago. Fuel gauge behaved normally for these 5,000 miles. The car then went in to have the front control arm bushings replaced. Upon getting the car back, the fuel gauge spins in complete circles. Not the normal "my car has no tank baffles" fluctuation while driving, but random pegging so hard to full that it actually does full 360s. My mechanic is blaming it on the sending unit, which of course he does not warranty. During the bushing replacement, plugs and wires were also replaced. I notice that the wires for the front 3 cylinders are suspiciously close to the 3 wire connector for the sending unit. My questions are-has anybody had this issue? How was it resolved? Will NOT resolving it cause damage to the gauge itself, or would it just continue to be an annoyance? The quality of materials, packaging methods and service from TFS has been less than impressive up to this point, so I would be lying if I said that I have a tremendous amount of faith in this sending unit. Thanks.
Barry

[This message has been edited by AstroBDean (edited 06-05-2014).]

Turn the key to on have someone sit in the car and watch the gauge and wiggle around the connector and wires to the tank.

you didn't say if you have stock fiero gauges or not. i would suspect the gauge itself. Put a meter on the gauge wire from the sender unit and measure ohms. Ohms should be 90 at full. if you get waaayyy over 90, then your problem is your sender or your wiring to the sender. if not, it's your gauge.

Thanks for the feedback guys. I'll have my wife watch it while I play with the connector. It does with just the key "on" (engine not running), if you sit in the driver's seat and rock left to right. I don't think it's actually getting a signal telling it to move past full. If the tank is nearly full, then it just pegs erratically to full. If it's more than about 1/4 tank from full, it seems it's pegging to full so quickly, that the inertia of the needle moving is enough to cause it to keep going and spin all the way around. They are stock gauges. It's an 87 MERA 5 speed on an SE chassis.