MoparFins

Techical Discussions => Tech- - Engine => Topic started by: Jon Doersch on April 25, 2009, 12:54:22 PM

Title: run on/dieseling?
Post by: Jon Doersch on April 25, 2009, 12:54:22 PM
What causes the engine to run on/diesel when you turn off the ignition? This just started happening on my 62 Newport with a 361. The only parts that have been recently changed are the mufflers, to a less restrictive design. The ignition is a mopar electronic conversion, and the carb is a Holley Street Avenger 670.
Title: run on/dieseling?
Post by: Ken on April 25, 2009, 03:29:50 PM
Here's a few answers from Wiki:
This condition can occur for a multitude of reasons:
carbon (http://en.wikipedia.org/wiki/Carbon)
in the ignition chamber can glow red after the engine is off, providing
a mechanism for sparking unburnt fuel. Such a thing can happen when the
engine runs very rich, depositing unspent fuel and particles on the
pistons and valves (http://en.wikipedia.org/wiki/Poppet_valve). Similarly, non-smooth metal regions within the piston (http://en.wikipedia.org/wiki/Piston)
chamber can cause this same problem, since they can glow red. It has
also been suggested that an improperly rated spark plug can retain heat
and cause the same problem.[/list]
idle speed (http://en.wikipedia.org/wiki/Idle_speed) that is too fast can leave the engine with too much angular momentum (http://en.wikipedia.org/wiki/Angular_momentum)
upon shutdown, raising the chances that the engine can turnover and
combust more fuel and lock itself into a cycle of continuous running.[/list]I'm betting timing, since you switched to electronic ignition, and it might even be related to a timing chain being stretched (too much slack) or skipped a tooth.



Title: run on/dieseling?
Post by: Snotty on April 27, 2009, 11:24:07 AM
Bad or old gas can be a contributor as well.  If you don't drive your car much (Fogel!!!) you will have bad/old gas in your tank.
Title: run on/dieseling?
Post by: Steve on April 27, 2009, 12:03:58 PM
That's the problem right there.  HOLLEY!
 
Probably dumping carb.  Could be fuel boiling in the bowls and borderline vapor lock.
 
Is it idling fast?
Title: run on/dieseling?
Post by: Jon Doersch on April 27, 2009, 05:34:33 PM
It idles at the same speed it always has, runs great at all RPMs, and is daily driven so it isn't bad gas. I was thinking about trying some seafoam, and some premium to try and clean up the carbon a little...then maybe swap to a cooler set of plugs. What does everyone think?
Title: run on/dieseling?
Post by: Steve on April 28, 2009, 07:26:08 AM
Seafoam is a good thing. . .If it's that bad, you might want to do it twice.  Must have a ton of carbon in it. . .
 
Do you take it on highway trips?  That helps too
 
Maybe treat the engine, and throw a can in the tank.
 
Does it slam into gear when you put it in drive or does it just lightly thump?
Title: run on/dieseling?
Post by: Jon Doersch on April 28, 2009, 04:19:27 PM
Its kind of hard into gear, and the shifts are pretty firm, although at a proper rpm. Why?
Title: run on/dieseling?
Post by: Jon Doersch on May 01, 2009, 09:09:52 AM
Update: used some seafoam and premium fuel and the problem is slightly better...