I have a 1989 f250 7.3 idi the front fuel gauge reads way over full and I switch it to the rear tank and it reads empty and the temperature gauge pegs out way over hot is this a ground issue?

 

Good place to start; often when unassociated electrical items affect each other it points to a ground issue.

 

in my experience, a fuel gauge that reads full is a ground issue,
one that reads empty sounds like a sender issue.
in both of my trucks I had issues with both tanks, it turned out to be the FSV.


FYI, the temp gauge in these trucks are nothing more than a glorified idiot light.


I hope its a ground, because the direct replacement FSV isn't cheap.

 

IDIoit How does the FSV affect the sender reading? What brand of FSV did you go with?
Thanks

 

The FSV selects which sender feeds the gauge. Way past full means infinite resistance, an open circuit somewhere. Empty means either zero resistance (a dead short to ground), or the float is compromised and filled with fuel.