Dual tank issue

[Slooptin]

I just picked up an 89 C30 (square body) and the guy I bought it from said it was having issues using the driver's side tank. right now the passenger tank is the only one that works and he told me that it was just the switch that needed to be replaced but I'm skeptical. I'm guessing its the fuel selector valve or a sending unit but I wanted to see what anyone else has done first before I order the new valve.

 

[1987 GMC Jimmy]

Have you played with the selector switch? Does the reading on the fuel gauge move or stay the same? If it moves, I wouldn't suspect the switch valve. If not, I would highly suspect it, but that's not a guarantee. In the meantime, here's a really good thread with schematics and charts in case this issue gets more complicated than you expected. This is courtesy of the forum's in-house wiring genius.

http://www.gmsquarebody.com/forum/showthread.php?t=11117