I replaced the sending unit in my 92 f350 front tank. It was always reading empty and now its always reading way over full. Faulty sending unit?

 

The sending units on these old trucks and van are notorious for failing. Did you check the resistance on your new unit before installing it?

Does your gauge read properly on the other tank? If no, then you might have some bad wiring, bad selector valve wiring, or bad gauge.

 

Most likely a connection issue. Way past full equals infinite resistance (open circuit). Does it work normally on the rear tank? If so, check wiring between the selector valve and the front tank.