What does the gauge do if you pull the wire off the tank sender?
Does the gauge go to below empty when you turn off the key?


Think about what would happen if....

If the sender is stuffed. It can read full or empty or anywhere in between.
If the float don't float then it will sink and read empty.
If the float arm breaks it can read anything.
If the fuel gauge wire rubs the body it can read full.

Nearly every time I have pulled a sender out of a tank the O ring has swollen up and not wanted to go back in. So do not pull the sender out of the tank until you are sure the sender needs changing.

I think that would have been me. I had to take it out twice to get the reading pretty close and the seal is fine.