You can bypass it with some pieces of tubing be sure to NOT switch to the tank that is not connected....

I would just open up the valve and have a look.
Looks like this inside:

http://i608.photobucket.com/albums/t...s/FUELRES2.gif

Take the 8 screws out and remove the rubber diaphragm.
(The diaphragm is not shown in the picture).
Push on the pins and see if the valves operate smoothly. To bench test put the diaphragm on and blow air into the inlet. Note which outlet port the air flows through. Then press the diaphragm down and the air should switch to the other outlet port. Don't try to disassemble the 2 valves any further! Real hard to get it back together - springs and "O" rings etc.

While the selector is off the rail, run the tank lines into jar or gas can.
There is a spec on how much fuel/min. Should flow pretty good but I don't remember the numbers? You will know if it is working or not. You will need to have a helper turn the ignition on and off repeatedly as the fuel pump relay ,via computer, will not allow the pumps to run longer than 3 seconds or so if the engine is not running. Switch to the other tank and repeat.

There is also a fuel filter in the bottom of the valve that you get to by unscrewing the bottom reservoir section. Last time I looked the filters were readily available.

I gave up on this valve and installed an electric switching valve: (~$60.00 for the valve delivered - Ebay).

http://i608.photobucket.com/albums/t...TankSelect.jpg

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I'm not saying it wasn't me because it very well might have been, but my truck now runs. The polarity of the new fuel pump was reversed. I do not think I could have screwed this up because the connection posts are different sizes. Before getting too into the job I re-checked everything, and found the problem. Hopefully this thread might help the next dude. Check the polarity.