1987 F-250, 351W with dual fuel tanks. I have a fuel delivery problem which I initially thought was the mechanical fuel pump. Here's the story. Driving down the road I got that "your running out of fuel" feel. Trouble shooting on the side of the road I determined the fuel pump wasn't drawing fuel from the tank. I keep a spare pump behind the seat so I swapped it out. Still no fuel from the new pump. I disconnect the supply line from the dual tank deverter valve (?) and dropped it into a one gallon 2-cycle gas can I had in the back of the truck. After a quick prime and few turns of the starter the truck fired up and ran. My question is has anyone ever had the dual tank deverter valve fail? Is it powered to one position (front or rear tank) at all times? If I disconnect the deverter input line from the fuel tank will it continuously run (gravity flow)? I don't want a big fuel spill in the driveway! Here is a picture of my "make shift fuel tank" which allowed me to make it home albeit sputtering from the 2-cycle gas!

 

Yes the fuel tank selector valve is always selecting the same tank when there is no power on it. You put power on it and it will select the other tank.

I do not understand your other questions.
You pull fuel through the selector valve from the selected tank that you have the switch on the dash set to. The switch is an off and on switch to the selector valve. When you put power on it you get fuel from the tank the switch is set to. Take to the power off and it lines up with the other tank.

No I have not seen one fail and I do not know how one would fail and block the fuel from the tank.

Yes you can by pass the selector valve and run the fuel line around it to either tank.
There is just a fuel filter and a tube in the tank. The fuel sender is mounted on this tube.

 

This was the second time in the last two months that the engine has shut off due to a fuel deliver problem. I haven't driven it much during that time maybe 80 miles. Both times it just stopped delivering fuel while driving down the highway. I tried switching to the opposite tank with no success. I wasn't aware of any filters within the fuel tank however, what would be the chance that both tanks had clogged filters at the same time? I suspect the deverter/selector valve. Any thoughts?

 

I think they did have a sock filter on the end of the tube.
Try bypassing the valve an run the engine hose right to one of the tanks and see if that helps.
I would guess that maybe something is plugging the hole going into the selector valve.