Thread: Engine wanting to run after shut off

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Some times not all the time my 327 still wants to keep running after i turn it off. what could be cousing this to happin? the timing off? ummm or the carb. loading up and still shooting fuel down into the engine or what? So what can i do? if you need any specs on the engine i'll get them to you.

Cd

Since you identified it as an intermittent problem, and assuming it's a modified engine (?), I'd check to see if there's bind in the throttle linkage or carb shafts, maybe the return spring. Sounds like the throttle plate (s) not shutting all the way. Could be you're on the edge of the octane requirement of the engine too, but the intermittent brings that to question. Timing, and temperature are also potential contributors, but I'd start with the carb/linkage.

ok, ya the engine is modified its bored .060 over and has a 3 stage over rv cam in it. 600cfm carb. brand new. im running 87 octane at the monent. it also has the vette heads on it big valve 350 heads. the performer rpm intake.

I will check the carb and see if it shuts all the way or not, thanx for you help bob.

cd

Your engine is heivily modified engine and your running 87 octane? you should be running 89 or higher. you should also replace your carb with a 650cfm carb and you should be good.

the carb is jetted at 690. had to jet it back down to 600 because it was getting so much fuel it wasn't burning it all so i was getting soot. i will try running on 89 im running 87 with booster.

thanx Cd

CD667;
Hey, if your engine wants to keep on running after you shut it off, that means you are taking it too easy while you are driving and all that energy is bottled up. Hehehe!

Anyways, the problem could be one of several.
A) your idle is set too high, it should be 800 rpm at idle if it is a standard and 900 if it is an automatic.
B) your compression is too high for the gas you are using.
C) it is running too hot.

Or you've got carbon deposits, sharp edges, or too hot a spark plug all of which can get hot enough to ignite the fuel and keep the engine running.

Originally posted by CD667
Some times not all the time my 327 still wants to keep running after i turn it off. what could be cousing this to happin? the timing off? ummm or the carb. loading up and still shooting fuel down into the engine or what? So what can i do? if you need any specs on the engine i'll get them to you.

Cd

Since this is so intermittent my suggestion may not apply, but not turning off can be from an electric fan back feeding the ignition or from a alternator that need a diode in the line to prevent back feed to the ignition system I have had both give me problem. On my 327 with an electric fan the engine seems to run on till the fan comes to an stop. This is a new project and will be on a seperate relay that I hope will prevent this. Ed ke6bnl

i got a cluch fan on mine with a 192 dre. in it

nice looking 327

MSD ignition Boxes sometimes cause run-on, that is if you have one installed!
My Ford was doing the same thing after a rebuild, Mine disapeared after going to a cooler plug.
Might not be the correct fix but it worked in mine!

what do the plugs look like?

the plugs are clean its running a little on the warm side. i mean there is sings of them getting hot but nothing major

what streets said about the throttle stop is usually what causes that problem on all gm cars in the seventies and up, but from the pic it looks like your running an edelbrock and I love those carbs I have never had that problem with them unless your fuel pressure is through the roof and its flooding out the vent or something I doubt its that if its a holley it they always piss out the vent tubes even with good needles and seats and proper fuel pressure. You can check this by taking the air cleaner off making sure the choke is open and just shut the engine off it you see a bit of smoke or haze from the carb after its off you know somewhere raw fuel is leaking down in the intake. As far as cheap tests
I would try cooler plugs and better fuel cheap start to find out what the problem is may be even a cooler thermo stat would help too if its running hot any idea on compression ratio forgive me if I am blind and didn't read it also how often or hard do you drive if you said it was running fat and sooting up carbon deposits could be doing it either being hot and igniting the fuel and or raising the compression ratio. Some say you can burn them out by gettin it on the road but the best way is to either take it down and decarbon the combustion chamber some with will say leave it together and use the walnut shell blaster which I know is a gm thing or may be a healthy shot of Seafoam in your fuel tank may clear some of that up. hope this helps...I have never heard of the backfeeding ignition one but I have had problems with aftermarket ignition doing all sorts of things I never would have checked that...hmm the fan spining made enough power to keep the engine running? I heard this somewhere else before weird oh well.

thanx guys for all the help i will try it. i have looked down the carb after the engine stops and i can see some haze coming up. i think the compression is around 10.25 to 11 psi.

I'm with tech inspector... the only time i ever had dieseling was thru heat...its a common misconception that it can be many other things... but it is worth checkin the temp...you say its a lil hot...how much is a lil?...colder plugs, new 'summer' thermostat,decent pump gas,maybe even some heatwrap on yer exhaust down pipes n manifolds etc are all inexpensive ways of tryin to fix this..the throttle stop thing is a poss but... the most common cause for it IS heat..i worked on all kinds o engines from 4 bangers to RB211 jet engines and the same can be said.... heat is the devil..
my 55 was a real pain in the ass, it used to diesel when i used it..i ignored it like a dork fer hella days...then i sat in traffic one day and the thing got sooo frickin hot under the hood that the petrol vaporized in the fuel lines...so i jus sat that like a dumb ass tryin to cool em down... try the easy fixes first....use good gas etc.... check ya ignition also etc... jus my opinion but, its a case of the usual suspects.. yknow