binfordm715 : Why won't my engine shut off? (Dieseling)

Why won't my engine shut off? (Dieseling)
Post by binfordm715 on Sept 22, 2006, 12:23am

I set the timing today, spot-on correct now. It runs quite a bit better now and I can tell it has quite a bit more power. Nick and I drove it around town today, for the first time since painting it. What a hoot!

But it still runs on when I turn the key off.

Help me out with the timing stuff here: Looking at the "vibration damper" with the markings on it, the manual has you set it 5* BTC, which is the 5 to the right of the 0. That's where I set it now. Before I adjusted it, it was 5* ATC(?), or on the 5 to the left of the 0. Probably past the 5, actually. And it dieseled on me then too.

Any quick-n-dirty ideas? Do I want to advance it a bit more? Would adjusting the idle mixture affect this? (I haven't set that yet, come to think of it, since rebuilding the carb.) Any thoughts?

Re: Why won't my engine shut off? (Dieseling)
Post by jeepistdougiowa on Sept 22, 2006, 12:28am

Don't forget to look over the balancer real good. The outer ring is ?vulcanized? to the inner with a piece of rubber inbetween. 39 year old balancers can deteriorate and the outer can shift in relation to the center...then who knows where in the heck your timing is.

Re: Why won't my engine shut off? (Dieseling)
Post by davea on Sept 22, 2006, 12:36am

Could also be carbon build up in the cylinders getting hot and igniting the fuel charge.

Re: Why won't my engine shut off? (Dieseling)
Post by thetroublemaster on Sept 22, 2006, 8:16am

What is your idle speed set at? I bet it's to high. When your throttle plates are just the slightest bit open, air can be sucked in to support combustion (bustin Tim) which is ignited by carbon build up or what ever heat source is making it burn. Turn your idle down a bit.

Re: Why won't my engine shut off? (Dieseling)
Post by brute4c on Sept 22, 2006, 8:52am

Yep....the Quirks manual says to set the idle down to prevent dieseling....I run mine down in the 525 to 550 area usually...I can run it down to 450 minimum...

Re: Why won't my engine shut off? (Dieseling)
Post by binfordm715 on Sept 22, 2006, 9:59am

If I can figure out how to hook up my dwell meter (I have to go read the other thread now!), then I can see what my idle is set at. It sounds low though. 650-ish. I'll try lowering it. Thanks!

Re: Why won't my engine shut off? (Dieseling)
Post by barrman on Sept 22, 2006, 4:29pm

Tim,
Just turn your lights on, start up the truck and turn the idle down until the volt meter shows your aren't charging anymore. What ever that speed is, it is as low as you can go.

Re: Why won't my engine shut off? (Dieseling)
Post by brute4c on Sept 22, 2006, 4:54pm

Hey thats good...thanks Tim!!

Re: Why won't my engine shut off? (Dieseling)
Post by barrman on Sept 22, 2006, 5:07pm

One thing to add. If you set it just above the speed the alternator can't charge anymore. Turn everything off and then restart. See if the alternator starts to charge without you touching the throttle. I have never messed with the stock alternator and don't really know how it is energized. I do know that some alternators need a higher rpm initially to start charging than is required to keep charging while running. The difference might only be 50 rpm, but it is big if you fire the truck up, turn on the lights while you are loading stuff up and warming the engine for 30 minutes, drive it 20 feet, turn it off while you make a before drive rest room stop. Then come back in 5 minutes to a truck that won't crank up.

Re: Why won't my engine shut off? (Dieseling)
Post by moosejr on Sept 23, 2006, 9:01am

You might try setting your timing by vacuum, and then see how far off your timing marks are, . .that will give you an indication of whether the timing mark is off on the dampener. I would tend to lean toward the idle speed, and make sure you don't have any vacuum leaks, and the vacuum advance is disconnected when setting the timing, the timing is set at the correct engine speed, and then when you connect vacuum advance, it goes to PORTED vacuum,...

You know, I almost forgot all I know about points and distributors, .. . then I got my M715 and have to go back and refresh on some "old school", ..LOL