I feel your pain with the wiring gremlins. They can be buggers to deal with. I take it you've checked every ground to make sure...bad grounds can do wierd sh...er, uh, stuff. Had a truck that had weird stuff happen with fuel sender and fuel guage. Did what you're doing. The tank, fule sender, wiring trace, etc. Turned out to be a burned out diode on the voltage regulator part of the PC board of the guage panel. A $2 part and 20 minutes of work to fix. Just thought I'd share.
I just bought a 92 B250. Dash lights won't work even after new fuse, new headlight switch. So I started looking the wiring harness under the dash. OMFG! This van came with an alarm,half assed installed and half undone by the time I got it. I would SOOO like to my hands around the neck of the moron who installed it and butchered so much wiring. Now I have the Dodge Factory shop manual that I bought on Ebay. What a help! I will get it figured out or replace the under dash harness. Then also like you, I have other items to fix...loose steering, coolant leak from the motor( that just started today), Probably end up doing brakes, shocks belt and hoses rather soon. Gave her a tune up last weekend because she started and ran ok, but the smell of running rich was almost as strong as a skunk spray. Plugs and wires had definitely seen better days, the air filter and PCV valve were so clogged I was surpised the motor could breath. She's running great now. But I digress...Good luck with the gremlins.
