1) With Front Tank switched on at the panel switch, the engine runs fine.
2) With Rear Tank switched on at the panel switch, the engine runs fine.
3) With Front Tank switched on, the fuel gauge is correct.
4) With Rear Tank switched on, the fuel gauge pegs Full with only about 3 gallons in the tank.
5) With Rear Tank left switched on, the hand will very slowly go down to reading correct (about 3 gallons). This takes 15-20 minutes.
6) With Front Tank switched on at the panel switch, the engine is using gas from the Front Tank.
7) With Rear Tank switched on at the panel switch, the engine is using gas from the Front Tank.

Questions: WTF is happening here? Would switched wires on the panel switch cause the rear tank to not pump and the gauge to read wrong? Also, can I use only one tank without replacing the dual reservoir with a single?

- Ford-Whupped in Alabama

 

On your truck there is a separate pump and fuel level sender in each tank and tank switching is handled by the dual function resovoir, so you have 2 problems.. a bad fuel level sender and a malfunctioning resovoir. And yes you could convert to a single tank by simply disconnecting and plugging the taps on the resovoir for the second tank.

 

For reference from Steve83: 1983 Ford Bronco '84-89 Fuel Reservoirs picture | SuperMotors.net