Hey y'all New guy here.
A few years back my fuel gauge started reading incorrectly. When I fill up, the gauge goes to just a little over 1/4 and at near empty it's below E.
The 83 Z has just under 20k original miles.
Could it be that ethanol gas has swollen the float and it sticks?
At least it still kinda works.
Any suggestions on how to fix it would be great.

 

Probably not. Which is not to say "the float is good", "the float doesn't fail", or ANY such thing; only, they don't generally fail in that way. Note the key words "probably" and "generally"; they're a good way to keep your logic logical, and out of "maybe it's this maybe it's that maybe it's the aliens" territory.

I don't think there's any possible way a defective sending unit can send the gauge below E. Sounds more like a gauge issue. Some actual troubleshooting, using logic, reason, discipline, etc., instead of random guessing, is in order. Disconnect the sending unit wire at the tank. With the wire disconnected the gauge should go to F, and if you touch the wire to ground, the gauge should go to E. (not below) Obviously nothing can be more grounded than ground, so if the gauge acts the same (goes below E) with the wire treated this way, it's defective.

 

I appreciate the info. I'll try that out this weekend.

 

I had similar issues with my gauge cluster. Volts read low, fuel was off, temp was off. I pulled the cluster and the copper traces where the terminal nuts are, were severely corroded. All green. Took some emery cloth and cleaned them up and it solved all my issues. Worth a look.

 

Thanks, I'll look into that.
How hard is it to pull the cluster?

 

I have a Firebird, I imagine removal is similar. Pretty simple. Remove the bezel covering it then remove the cluster. Just screwed in. Not sure if you have a mechanical speedo cable. There are videos on Youtube on how to do it, but I'd follow Sofas recommendations first before you go ripping and tearing. It's a pretty simple test.