Hot Rods engine won't shut down

The engine keeps running when I shut off the ignition switch. I don't know where the power is coming from. I set up a system like Crazy Steve suggested in wiring 101 from scratch. Everything is working great on the car. Except shutdown. It is a 28 coupe. The distributor has petronics in it.
The ignition switch works properly, but when I shut off the key there is still power to it from somewhere. Can't seem to figure it out. Here is a quick diagram. I am sure you guys can set me straight.

 

You probably need a diode in the white wire coming off the alt, its back-feeding power to the ignition while running.

 

The alternator is still producing power when the switch is off.

 

Put white wire to ACC.

 

This brings back fuzzy memories from 35 years ago. Had the same problem in a SBC powered 40 coupe. IIRC the one wire alternator was the problem. These guys seem to be leading you to the solution.

 

do you have an electric fan on your radiator? If you do, and you are not using a relay, the fan's motor will create electricity as it keeps spinning for a few seconds after the ignition is turned off. When I first installed mine on my 38 Chevy I wired it with just toggle switch. I would shut off car using the key and the car kept running for 5-7 seconds. I added a relay and a temperature on off switch and it solved the problem.

 

Tried the easiest first. Moved the white to acc and it shuts down now. I knew it couldn't be a huge problem. It makes sense now. Thank you all for your fast input.

 

I had the same problem with my old '40 Ford pickup. Had the electric fan hooked up to the "run" side of the ignition. When the ignition was turned off and the fan was winding down, the fan motor would generate power back through the ignition and the engine would "diesel" until the fan stopped.

 

As mentioned above move alternator wire to acc.

 

As 3 spd and others mentioned the alternator is feeding back to the ignition.
You can fix it with a diode

You can fix it with a light


Or you could even put a switch in the white wire to break the circuit when you turn the engine off meaning that you would have to flip the switch and then turn it back on when the engine stops.
Or move the wire to the ACC post on the switch.

 

I listen to the radio in my car, with the ignition off sometimes. I like having the ACC position free to do that, without turning on the ignition and engine management.

I run a diode.

Also if that Pertronix is an Ignitor I (not a II or III), accidentally leaving it on can burn it out.

 

Thanks Guys. Yes I will move it back to ignition position with a diode. I never thought of the problems associated with having it on the accessory post. Great info.

Reyn

 

Your diagram suggest's a universal switch. That said, do you have a true ACC only position or do both IGN and ACC come on at the same time on your switch?

 

If you have a Massey Ferguson tractor dealer close by or maybe a Ford New Holland dealer you can usually get that diode from them for a couple of bucks.

 

Yes it is a true acc position.

I'll check that out.

 

I prefer a brass starter button.

All those safety switches add resistance to the circuit.. The contacts in the ignition switch are usually worn out pretty good. After all, those switch's were only designed to last 10 years or so.. Either a stand alone button or use the "start" on the ignition switch, to close a solenoid connect the line side to the battery and the load side to the starter..

 

I wire my radio's hot. Before anyone tells me I can drain the battery that way your guilty of leaving your dome light on all night.