[MV] M715 Dieseling--One Final Observation

Mark Masse (mmasse@islc.net)
Sat, 10 Oct 1998 16:36:39 -0700

Although a tune-up always seems to cure my post-shutdown dieseling, I
decided to test the "hot spot in the cylinder" theory.

For the last few weeks, my truck has dieseled upon shutdown. I usually kill
the engine about 5-10 seconds after pulling into my driveway. Lately I've
pulled the choke out ALMOST to the point where the engine begins stumbling,
and let it idle there for about 10-15 seconds before un-choking it and
immediately shutting it off. This procedure seems to have eliminated
dieseling after shut-off.

This would suggest that there are, in fact, some hot spots in a few of the
cylinders. Choking it prior to shutdown enriches the fuel-air mixture.
Adding enough fuel will cool the hot areas down so that they are no longer
sources of ignition.

Now the only concern I have is cylinder wall glazing due to an overly-rich
mixture. I don't think that 15 seconds of rich mixture will do much
harm--at least I hope it won't. The plugs, for the most part, have a light,
powdery red coating on them (red presumably from the reddish lead substitute
I add to the gas).

--Mark Masse
1967 Kaiser M715

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