I've got an 89 F-150 300-6cyl with the granny 4speed, we had been four wheeling and a friend hit a tree head on, then slide done the right side fender (pretty much scraped the whole front clip) anyway ever sence he hit the tree the gas gauge is pegged pass full, I pulled the intire dash out becuase the little weight had fell off of the hand so I put that back. It works as long as you don't turn the switch on then it peggs when you put power to it. Any ideas what the problem could be? :banghead:

Sender wire shorted to frame?

your fuel sending unit came apart .i would think

Sender wire shorted to frame?
I think a short gives you an "empty" reading...(1) you might have pulled the wire loose from the tank, or (2) the little circuit board behind the instrument panel (the one that that acts as a "slosh module" for the gas gauge) could have been jarred loose/damaged in the tree bump incident.