My '92 F150, 300 I-6, 5 sp has the fuel gauge pegged at full. It doesn't move, even with the key off. Shouldn't be an in-tank gauge problem, since it stays this way on the front & rear tanks. Is it a bad gauge in the dash or is there something else that could cause it to stay pegged?

And, please, skip the cute comments about how your gauge always seems to be on "E"................

 

The factory Ford manual states that if the "gage reads full at all fuel levels"
1. Short circuit in wiring
2. Sender arm movement obstructed

Sounds like the latter is void since it reads the same on both tanks.

It does not indicate that there would be a problem with the gage itself...
If it is I would think it would be a mechanical reason that the gage stays there, ie. movement of the gage is obstructed.