My fuel gauge is wrong. When full, it only shows about 3/4 tank. The red/low fuel light comes on when I burn through about 14 gallons of fuel.

I replaced the fuel float sensor in the fuel tank. The old one was doing the same exact thing as the new one I replaced it with.

When I shorted the two pins at the anti-slosh relay, nothing got any better.

Any advice?

 

The Great Palm is very good on how to clean the instrument electrical pathway. In my case the gauge read too low, and in the end I took the binnacle off and did all the things palm suggested. It cleared the fault. basically the current to the instrument is very low, and any, absolutely any slight, almost invisible corrosion or other slight insulant will give this problem. The current has to pass from the blue flexible track to a tiny self tapper then to a copper contact and there are loads of places even a small reduction in the conductivity will affect the gauge.

 

When I pulled the sender out of a series III sedan the float was partially full of fuel. It's possible that everything is fine electrically, but not mechanically. You may have a partially sunk float.

EDit: nevermind, I just saw you replaced the sender.

 

Sender is a fast check because it should vary between 20-220 ohms from one end of the range to the other.

It seems like you are generally having gauge issues. I've seen it recommended a few times to add an extra ground to the cluster in addition to usual cleaning.