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i have my 1984 f250 diesel with dual tanks,when i switch to the rear tank the truck runs for a very short time and wants to die.also,when i switch to rear tank the fuel guage goes to empty even though it is full.i have checked the sender and it works fine,no cracks on tube either. i have replaced the selector valve underneath the truck with the same result.i am thinking it must be the switch on the dash.thanks for any replies or confirmations.
With the engine off and the key On, when you change tanks you should be able to hear the selector valve switch tanks. A little ziiiiiip sound.
I founf I had a connection problem on the wiring connector on the selector valve a couple years ago. A wire tie installed in the correct position fixed it.
Another problem you may be having is the O rings in the fuel line connector at the sending unit and at the selector valve. Since you have removed and replaced the connectors before, possibly one of the O rings cracked and is leaking air into the fuel lines.