Hi 86:
Sorry I dont have a wiring diagram for a 86 model...do you have the glove box manual? If you do, it should show what all the fuses are for on the fuse box. If you dont have it, get down there and see if any of them are blown...if you see one that is blown it may be a circuit the fuel tank selector valve is on and so the valve is stuck on one tank that is either dry or clogged up.
If it turns out the selector valve is ok, other things to check out are:
-fuel caps...are they venting the tanks properly
-fuel tank vent lines...are they open and venting to the atmosphere or the EVAP cannister?
-rubber fuel lines from tanks through selector valve...are any split or cracked...if so, they could be preventing fuel pick-up.
Regards,
Henry