I have a problem on my 84 diesel truck, where the FTSV stopped working. Replaced it with a valve from my 87 diesel parts truck, connecting wires to the 87 plug. Fuel gauge records rear tank fuel level also when cab switch is set to front tank. Fuel will only come from rear tank, even when cab switch is set on front tank.
Could someone provide me with wiring diagrams for the 84 & 87 FTSV's or typs on how to solve this puzzle?

 

Here is one for an 1983, the 1984 Diesel is the same diagram except there is not a pump in the tank.


Here is one for an 1988 the 87 should be the same.


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Thank you SUBFORD/Bill for the quick reply. Will have to see now if a re-wiring is possible to make the selector work.

Merry Christmas, Uchitz