Fuel Selector on 1990 Ford Econoline

Hello,
I'm having trouble figuring out how the fuel selector works on my 1990 ford econoline w/a 351 EFI engine. It will not switch over to the forward fuel tank (and that tank reads empty) but my van will not die on me (I believe it is still pumping from the rear tank?). It works well off the rear. I know I have a switch inside that has 6 conductors (I have check all conductors functionality with a ohm meter w/switch in both positions). The switch works, but I believe I have a faulty selector valve. I cannot figure out how it works, though. I can find no electrical leads going to it. I only see 4 lines going into it (2 from each tank) and 2 leaving toward the front of the vehicle (one goes to a pump then to a filter, don't know where the other one goes or what its purpose is). This doesn't make sense to me. Is this the selection valve? Or is the fuel selection made by disable and enabling the booster pump (I think I have these) inside the tank and this is serving as a merging point (with no selection made at this point)? If so, I know that I may have a bad fuel pump. I know I am long winded, but I want anyone who knows to understand my problem. I appreciate any help!