Pull the bulkhead connector (firewall) apart and clean all the contacts first, and make sure none of the contacts are pushing back thru the plastic block. You may find a burned connector. Afrer it is bolted back together after cleaning, It helps to have a friend there to push on each wire from one side, while you push from the other with a small screwdriver.
I have had this trouble on my 84 and 83, but it was lighting circuits. Use dielectric grease before bolting the connector block back together. Check for hot to the ignition switch also. If you have hot in, but not out, bingo. I had a switch go bad and had the same symptoms.
I hope this helps.

84 D150 440/727
79 /6 swb D150
1964 A100 window van. Just because it has spark plug tubes doesn't mean it's a Hemi.



If ya haven't been there, ya just wouldn't understand.