Electrical Gremlin causing engine run-on

[cooter55]

The patient is my '73 C20 2wd 454 w/TH400. When I turn the engine off, it will sometimes continue to keep running but not smoothly. Acts like it's dieseling but it's electrical. The radio will continue to play. Sometimes when I close the door hard, I'll come back and the radio is on. It appears to be some kind of ignition 12v that is crossing over. If I pull the ignition 12v for the radio from the fuse block, the radio shuts off. If I disconect the 12v ignition to the distributor(HEI with clean ignition wiring) the engine will shut off. I believe I'm getting a 12v battery to 12v ignition crossing over somewhere. This weekend, I'm going to check and clean wires and terminals on the starter and replace the ignition switch down on the column.
Can anyone think of any other areas to check? This thing has me baffled!

 

[crazy4offroad]

Ignition switch would be my first guess.

 

[cooter55]

solved the problem

Changed out the ignition switch but the problem remained. Crawled under the truck and sure enough...the battery lead to the starter solenoid was just barely touching the ignition post, resulting in a weak feed to the 12v ignition circuit. Moved and tightened the battery lead and the gremlin is gone.

 

[89Suburban]

No ****? Good job Jack and thanks for reporting back.