MaxDog

couple times in the last few weeks, my 72 442 with a 350 4bbl has sputtered for a second or two after I turned the key off. Today, it actually sputtered for about 4 seconds and then a puff of smoke came out from under the hood!!!!!

I looked under the hood but couldn't tell where the smoke came from. What should I do??

Any advice would be greatly appreciated. Thanks.

Lady72nRob71

Sounds like dieseling or run-on.
That could be caused by overheating, too lean mixture, improper timing, or excess carbon in the cylinders. My guess is that the smoke came out the carb.

MDchanic

It's dieseling.

Lots of things can cause it, including too high an idle setting, non-functioning or missing anti-dieseling solenoid (it it had one originally), too hot an engine, carbon build-up in the combustion chamber, etc.

You can go over all this stuff and will probably find the cause, but until then, just shut it down in gear and it won't do that. (Though I did have a '68 Merc. Colony Park wagon once with a high-comp. 390, that I could drive down the block with the ignition switch off - you wannna talk about nasty acrid exhaust fumes...).

Oh - the smoke is blow-back through the carburetor.

- Eric

edit: Rob, you beat me to it by seconds...

MaxDog

Thanks. I have a timing light with an rpm meter built in, so I will start with checking the timing (especially since it has a strong exhaust smell) and making sure the idle is not set too fast. I will also get one of those heat meter tools to check the temperature. Now that I think about it, this didn't start until it really warmed up here in vegas the last two weeks. Friday it was 112 degrees.

Not sure how to check the following though:
-Missing/non-functioning antideiseling solenoid;
-carbon build up in combustion chamber;

knighthawk

get one of them anti- deisel solenoids, or what I call them : the fast idle solenoid they use for AC. Key on, they hold the idle up (put ot at 6 or 700 or whatever), the when you turn the key off it drops to something really where it can't idle

Lady72nRob71

Check for vacuum leaks - they will cause a lean mixture.
I do not think this car came with an anti-diesel solenoid, so I would not worry about trying to install one. Best to find the real problem and solve it.

I would start with RPM, timing, and temperature. Since it started in high temps, I would start looking at the engine temp. Bad fan clutch or undersized radiator could be issues.

To check carbon buildup (last check), pull a few plugs out and look at the piston tops with a good flashlight. If you see more carbon than metal, there may be too much in there. Report back what the plugs look like - that will tell you something.

MDchanic

Hi Max.

Check your Chassis Service Manual to see of your engine was originally equipped with an anti-dieseling solenoid.
If it was, then you may be able to get one from a junkyard or a fellow member. If your engine or carb is highly modified, you'll have to use your imagination and judgement.

As for carbon deposits (which can get hot and cause preignition), you can't tell without pulling the heads, but you can clean or replace your spark plugs if they look like they have any crud on them.

Also, do you gave a temperature gauge?
If the motor was unusually hot, that would explain it.

- Eric

MDchanic

Help!!!

Rob is stalking me!

MaxDog

Thank you gentlemen!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Lady72nRob71

I have had people tell me that I would be a good stalker, mainly from how quietly I walk. I have unwillingly snuck up on too many people and scared the living crap out of them.