Hi all,
My 87 GT has a fuel gauge that reads to high. When full it reads way above full and when empty it reads about 3/8 of a tank. I'm thinking a bad ground at the tank. What do all of you think?
Thanks,
Daryl

quote Originally posted by Daryl M: Hi all, My 87 GT has a fuel gauge that reads to high. When full it reads way above full and when empty it reads about 3/8 of a tank. I'm thinking a bad ground at the tank. What do all of you think? Thanks, Daryl

When did this start? Did it just recently start to do this, or has it always done this and it's a car you recently acquired?

No uncommon.
The fuel sender operates on a resistance circuit (0 - 90 Ω).
90 Ω is full.
There is either added resistance in the circuit or the gage or sender is out of calibration.
Added resistance could be from corrosion in the sender, a connector or grounding point.

quote Originally posted by 82-T/A [At Work]: When did this start? Did it just recently start to do this, or has it always done this and it's a car you recently acquired?

The guage has not read accurately since I biught it i 2017.

Forum member JGunsett offers gage recalibration services.
You can sender calibration with a DVM, and gage calibration with the proper value resistors.

After reading your posts and checking an old post from 2016, i disconnected the connector at the firewall (502 I think) and tested there. The guage works properly. I then cleaned the connector and reconnected it and the guage reads just barely below full with about 10 miles since i filled the tank. Before testing it read way above full. I'm thinking that the connector was dirty or corroded a bit. Guess ill see when I run out of gas.
Daryl

[This message has been edited by Daryl M (edited 10-10-2019).]