87 Dual tank selector problem

[DieselSJ]

My selector started acting up a couple weeks ago where it didn't want to switch tanks. Truck would die if I switched from my left to right tank. Fast forward to last week and same thing happened again, but difference was when I flipped the switch the fuel level gauge pegged and the truck died. Got it to switch back to the left tank and all seemed fine. Then got smell of burning electrical. Pulled over a couple times to try to track down the smell and traced it to the ECU. Truck started running horribly but managed to get it home.

Replaced ECU with Delco reman, plus new tank selector valve and new switch.

Got everything installed today and having same issue with fuel selector valve. Flip switch to right tank and fuel gauge pegs past full and truck dies. Interesting thing is that if I flip the switch back nothing happens until I turn off the key and turn it back on, then the fuel gauge reads back on the left tank and the engine runs.

Got under and checked some wires for obvious shorts and didn't find any. Tried the valve again and everything worked fine after that - engine ran on both tanks and fuel gauge was fine.

So it would seem that I have a short somewhere. Any other thoughts?