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Author Topic: run on/dieseling?  (Read 815 times)

Jon Doersch

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run on/dieseling?
« 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.
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Ken

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run on/dieseling?
« Reply #1 on: April 25, 2009, 03:29:50 PM »

Here's a few answers from Wiki:
This condition can occur for a multitude of reasons:
    Built-up
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. Similarly, non-smooth metal regions within the 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]
  • A carburetor that does not close entirely can contribute to running once the engine is off, since the extra fuel and oxygen mixture can combust easily in the warm piston chamber. Similarly, hot vaporized oil gases from the engine crankcase can provide ample fuel for dieseling.
  • Incorrect timing.
  • An engine that runs too hot or too lean may produce an environment conducive to allowing unspent fuel to combust.
    An
idle speed that is too fast can leave the engine with too much 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.



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Snotty

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run on/dieseling?
« Reply #2 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.
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Steve

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run on/dieseling?
« Reply #3 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?
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Jon Doersch

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run on/dieseling?
« Reply #4 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?
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Steve

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run on/dieseling?
« Reply #5 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?
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Jon Doersch

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run on/dieseling?
« Reply #6 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?
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Jon Doersch

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run on/dieseling?
« Reply #7 on: May 01, 2009, 09:09:52 AM »

Update: used some seafoam and premium fuel and the problem is slightly better...
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