Electronic Ignition Can Surprise You

[LarryM]

I recently shut off a tractor with Petronix and when I turned the key on 2-3 minutes later it started. It seems to fire every time you turn on the key. The motor was just in the right spot to fire and go. That sure could be dangerous if your not aware of it.
 

[CNKS]

Wired wrong or something wrong with the switch.
 

[JMOR]

[Janicholson]

The key in a points and coil system (and your electronic system) is just one more switch in the path of electrons. When turned on, or off it can spark. My uncle had a 400 farmall start and run (in reverse) for a big spiral in the barn yard that ended with the 3 16s FH plow in the tack house, and his wife shutting it off by wiggling the defective Key switch. Jim
 

[mkirsch]

I have heard stories of tractors starting during lightning storms and driving off on their own.
 

[John G. Hasler]

The classic Kettering circuit can only generate a spark when the current through the coil is interrupted (obviously, the defective switch in your uncle"s tractor managed to interrupt it). Thus it cannot fire at turn-on under normal circumstances. The Petronix system is a bit more complex and I can believe that it can generate a spark on turn-on, though it should have circuitry to prevent this.
 

[CNKS]

You don't see a question mark -- something is defective, as it should not do that.
 

[scotc]

And diesel pickups with a manual trans driving off on its own after the owner replaced the fuel shut-off solenoid with a cable, and it then got hit in a parking lot.
 

[kossuth]