Amazing how much we've forgotten from the days before computers and fuel
injection came to cars and light trucks.
This used to be called "dieseling" and that pretty much describes it. When
you turn off the ignition, you only kill power to the spark circuit. The
fuel system is still fully functional and there is still compression when
it turns. If there is a hot spot on a piston surface or on the head, it
will ignite incoming fuel and the engine will stumble on until the spot
cools down. Since this usually happens in only one cylinder and the
"timing" of the ignition source is way early, it runs very rough and the
exhaust smells horrible.
Several things to try:
1. Check the heat range of the spark plugs. The heat range determines how
hot the electrode runs, not how hot the spark is. If the heat range is too
high, the tip of the plug can get hot enough to cause this. Back in the
days of leaded fuel, the lead deposits could also cause this.
2. Pour a glass of water SLOWLY down the throat of the carb while the
beast is idling hot. Do it slow so you don't put the fire out. The steam
generated in the combustion chambers will sometimes knock the deposits
loose.
3. If all else fails, pull the head and clean things out. It should then
go away. There could also be a burr or rough spot somewhere in there that
acts like a glow plug and causes it.
Unless the timing is contributing to the engine running hot otherwise,
engine timing has nothing to do with this.
If you don't have an auto, put the thing in high gear and pop the clutch.
The truck will buck, but the engine will stop.
Blessing every minute I spent with my dad working on these things when they
weren't so oletrucks...
Bruce Kettunen
57 3200
>All right,
> My trucks don't exactly fall quite within the category of a "'41-'59
>GM or
>Chevy." However, within the next few weeks I will be purchasing a '55-'57
>Suburban or Panel, to be converted it into a "Blazer" so to speak, with a
>short
>wheelbase and one piece rear quarter windows (no post). Right now I own a '61
>step and a '64 fleet, both shortbeds. So, my question is this; I know
>you've
>all experienced this one. You take your newly waxed truck out on a nice clear
>Sunday afternoon drive. You reach your destination and pick a spot to
>park in.
>With on-lookers admiring your Oletruck you pull in and twist the key to the
>left. But instead of the tach quickly dropping to zero, the crank almost
>stops
>turning, only to change its mind and give a few more kicks! Sometimes it sits
>there, sounding like a dying animal for up to a minute. It almost sounds like
>it's turning backwards. In fact, the next time it happens I should jump
>out and
>pop the hood to see.
> So, I've been told that if the timing is too far advanced, it can cause
>this. What I don't understand is why there would even be spark with the
>ignition cut off. In which case, the timing shouldn't matter, right? I
>do know
>that it only happens when the engine has had time to warm up (at least a
>10 min
>drive). And, it seems the warmer it is, the longer it takes to die.
>Could the
>cylinders/head be hot enough to ignite the fuel? This is a 235 in the '64
>fleetside by the way. I'll try to adjust the timing when I get a chance, but,
>if that does fix it, I'd still like to know why.
>
>
>Mike Dempsey
>Pre '67 Fan
>
>
>oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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