Truck Started Cranking By Itself, key in the off position.

Hello- (again)!

I've got another question about a Paccar, although I don't think the engine type matters here.
I was at the yard working on another truck, when out of the blue, the Paccar starts to crank! The truck never turned on, just kept cranking. The key WAS in the ignition, in the OFF position. The truck continued to crank, even after I pulled the key out!!
I disconnected the battery to disable the truck.
It was a cool, breezy, rainy day. Not sure whether that matters.

Where do I start? (No pun intended.)

Any ideas?

 

Does this truck have the ability to start to charge low batteries or warm the engine? I'd start there if it does. If not, I'd start at the starter solenoid and work my way back to see what's feeding it power.

 

Thank you! It is not equipped to top off low batteries or warm the engine on it's own.
I'll check at the starter solenoid per your suggestion. . . That's where my mind went too. Thanks again, I'm just scratchin' my head about what initiated the random, impromptu cranking.

In any case,
Kind regards

 

I had the truck starter crank over while I was driving. It ended up to be the cables wearing thru the insulation which eventually passed current to crank the starter over. This was on my 1979 KW. My guess to your issue could of been similar however, the rain(moisture) gave it that extra boost.

 

Thanks for the reply!
I can only imagine the expression on your face when that happened! Probably looked something like mine this evening. It was already getting dark outside when I was tinking around with the lights on the other truck. I'll have to crawl under and take a good look at everything during daylight. . . I'll be sure to check for what you've described with the insulation. That sounds very plausible indeed- especially with the rain!

Love the look of those older KWs!

Thanks again for taking the time,

Cheers!

 

Had a machine light up inside the washbay one time because of rubbed through insulation on the positive cable. Was fine until the water hit it, then I'm yelling at the nearest apprentice to grab a wrench and unhook the batteries while I kept the water spray on the fire to keep it from going up lol.

 

If that happened wouldn’t the starter have been spinning about 100,000 rpm’s?
I can’t believe it didn’t explode or did it?

 

Do starter drives not have a one way slip clutch so they do not stay at speed when the engine fires?

 

They do when you are trying to first start the engine but he said his engaged when the engine was already running.
I’m not sure how he could have even heard that.