My fuel gauge on my cvr es 1999 when I switch off it stays on like half full, I have only had the car one week, it was on full after me filling it up but after a long drive is working okay.
Do they all stay on as my old ford go's to empty after removing key.

 

Welcome in,i had the same problem with my Ford truck and Corvette ,i put a bottle of Seafoam in a full tank of fuel ,the truck took A second treatment but it cleans the sensors in the tank. Try it, it only cost $8.