1986 2.8 gt 4 speed. Ok so bought a pos sending unit from the fiero store about 2 months ago. And damn I regret getting this crap a** part. It is so inaccurate it’s ridiculous. 160 bucks down the drain on something I thought would cure my fuel reading problems. So the problem I’m having is it will read 3/4 when full but slowly creep up to full. Once I start driving it will drop to a half then back up to 3/4. Like wtf is going on I did literally 20 miles of driving today off the trip meter after filling up and now it’s pegged on 1/2 tank when I know it prob only burned a gallon. What is everyone doing to fix this issue since the fiero store is telling me that there is no faults with the part and that they test them before sending them out. Where do I check I’m guessing faulty gauge but when did the sweep for resistance check it worked perfectly fine.

If the gauge sweeps OK then the problem must be in the sender. Did you check the sweep on the sender? One other thing is that the float on the sender could be binding. As you describe the problem it sounds like something is hanging up and then frees itself.

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Mike in Sydney

[This message has been edited by Mike in Sydney (edited 10-17-2019).]

Have installed a few of these, no problem with them.

The gauge or wiring maybe the problem even if sender test good.

Fiero Gauges have a "ballast" resistor and contacts that get dirty loose etc. Dash itself can have crap contacts too.
Wire(s) to tank can have problems.

Worse, All can be constant or intermittent problems.

Note that Sender/Pump ground ends in the cabin and iffy ground don't only causes sender problems but can kill the pump too. Buying a new pump can kill that quick too.
See my Cave, Electric Motors

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

I thought that some of these needed massaging because they have a chance of hitting the baffles?

I have had mine for 2 years and it works fine, actually very accurate.

quote Originally posted by Spadesluck: I thought that some of these needed massaging because they have a chance of hitting the baffles?

Thread from earlier this year... Fiero Store gas tank sending unit

When I installed one in my 86 I tested and found it hitting the baffles. I had to tweak the float until all cleared. Ok since.

Yep, I bet the float is hitting the baffles.

The Fiero Store unit I bought even had a warning on it to check for clearance and bend the float arm, if needed.

I did need to bend mine. But, I wasn't 100% sure it was fixed until after I hooked up the ohmmeter to the unit and flipped the tank upside down over and over again to ensure it went from 0-90 without hesitation at every possible angle.

quote Originally posted by Patrick: Thread from earlier this year... Fiero Store gas tank sending unit

Thank you for the link. I just replaced my sending unit with FS one and it will only show 1/4. I tested it before dropping it in the tank and it was good.