[95 S_Trucker]

This should be posted in the 88-98 section

The front tank has a high pressure pump that supplies fuel to the engine. There is a balance module that gets inputs from the sending unit of each tank. The balance module used that info to operate the transfer pump that pumps fuel from the rear tank to the front tank. The balance module also sends the computed fuel level to the fuel gauge.

You could have a sending unit problem, a module/wiring problem, or a bad transfer pump.

My 96 had this system. I had to remove the rear tank when I put the rollback bed on it.

I have some diagrams somewhere. I will post them when I find them.