Seems to be intermittent, but there are times when my engine will keep running after I turn the ignition off. No, it's not a pre-ignition ( dieseling ) problem. The ignition is getting power from somewhere other than the ign. switch. Any ideas? I'm think ether my 1 wire alternator or possibly my electric fan motor. Haven't done any trouble shooting yet. If I can get it to do it, I will start pulling fuses. Thanks, John

When it happens, does it shut itself off after a few seconds, or are you doing something to shut it off?

There are several places it can potentially be back feeding the ignition, the 1 wire alt would be a good place to start. Past that, I believe I would look for a relay hanging up. Its going to be tough to find if its intermittent and only lasts a few seconds. Good luck! Gene

what type of ignition switch are you using ?

"Painless" # 910-12209 from Speedway. It's rated at 20 amps - not a cheap switch @ $52. When the problem does occur ( key in the off position ), the engine will stutter run - on off on off on off. Last time it happened I actually had to pull the coil wire to shut it down. When I went to start it back up, all was fine again - shut down normally.

wasn't sure you had the dash mounted switch you have, or a column switch. i have seen the column switches of various brands melt around the connections and at the switch spades leading to just the symptoms you describe. i can't tell from the pic i have of that switch [in the speedway catalog], but is the connector a push on, or does each wire have a screw attached terminal ?

Wires coming off the back of the switch are actually "potted" - no wire connections on the back of the switch.

Might need a diode in the line to the ignition circuit maybe? (MSD for example mention it for when a back feed through the charging system causes run on..). Fans usually seem to be run on relays so shutting the ignition should kill the power to the relay you'd think unless it was energizing still too, diode could be tried there as well perhaps ?

shows you how long ago it has been since i bought a switch of that type ! the last one of those i bought for my 38 plymouth coupe [around 1981 or so] cost somewhere about $6 and had screws retaining individual ring terminals that accepted 12ga. wire. if i remember correctly, it was made in this country by/for standard products. maybe tempted to pick up a couple if i see those type at a future swap meet. for future projects i probably won't get to in my life time.