I have a 88 ford e150 conversion van that has two fuel tanks, The switch for these tanks will register correct on the front tank but when I switch to the rear tank the gauge reads completely empty even though the tank is full.
It doesn't seem to interfere with the operation of the vehicle it will continue to run in either position therefore I don't think it is a fuel pump problem.
It is just a nuisance to have to guess as to how much fuel is in the rear tank especially on long trips.
Any help would be appreciated

 

Thread moved to Fuel System forum.

-Matt

 

You have high resistance from the fuel selector switch to ground and could be any of the following:
1. Bad contacts in fuel selector switch or wire connection to switch.
2. Open wire or bad plug connection.
3. Sunk float in tank.
4. Bad sending unit in tank. (Normally 8 Ohms full and 85 Ohms empty).
5. Bad wiring to ground from Sending unit.