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engine still runs after turning key off


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robster
User

Dec 21, 2014, 1:08 AM

Post #1 of 12 (1401 views)
engine still runs after turning key off Sign In

hi, my engine still runs after i turn the key off then dies after few seconds, what could be causing this?
thank you....


Tom Greenleaf
Ultimate Carjunky / Moderator
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Dec 21, 2014, 1:25 AM

Post #2 of 12 (1392 views)
Re: engine still runs after turning key off Sign In

For goodness sake sport, what the heck is this? A generator, car lawnmower or what? Jeez, an engine shuts off when you turn key to off so what's the problem?


Sorry - please describe what this is and a bit about what really happens,


T



robster
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Dec 21, 2014, 6:13 AM

Post #3 of 12 (1377 views)
Re: engine still runs after turning key off Sign In

hahaha! honestly yes, i witnessed it with my two eyes and two balls, i mean my eyeballs... my car is a 1977 carbureted 1100cc engine using SU carb. after a few miles of driving and i turn the key to off, engine still runs for very few secs then dies., am i running rich? if yes, where is the spark coming from to ignite the fuel after turning the key off.??




(This post was edited by robster on Dec 21, 2014, 6:24 AM)


Tom Greenleaf
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Dec 21, 2014, 6:35 AM

Post #4 of 12 (1371 views)
Re: engine still runs after turning key off Sign In

Is this issue new to this machine? A carbed engine with either gravity fed furl or engine mounted pumped fuel would continue to get fuel and run......... IF SPARK WAS STILL PRESENT, OR PERHAPS IF COMPRESSION (EXAMPLE) WAS SO HIGH THE HEAT OF COMPRESSION WAS STILL IGNITING FUEL. We called that "dieseling", run on and other words. This is exacerbated by higle RPMs when shut down, a hot engine and more if that.


You need to see if spark somehow continues or not while this runs on with key off to know much more I think. Those engines that do that do not run properly for that period of time if still running without spark - some might end up with a back fire and quit.
Measure this time with a stop watch please to exact what "seconds" really means.


Some vehicles of back when would run endlessly without spark and had to force them to quit.


IMO if this is always running rich it would have other problems when running up to showing black exhaust, black dirty plugs and possibly carbon build up in cylinders making compression way too high, hence heat of compression alone could fire it on much like a diesel does by design - heat of compression. Gas engines use spark,


T



Tom Greenleaf
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Dec 21, 2014, 6:39 AM

Post #5 of 12 (1367 views)
Re: engine still runs after turning key off Sign In

You posted pic after my post. I suggest taking all that garbage off and back to OE which should just letting go of throttle AND turn key to OFF should be enough to stop running. OE devices were common OE to help stop a run on problem. Now you lack all that,


T



Hammer Time
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Dec 21, 2014, 7:29 AM

Post #6 of 12 (1360 views)
Re: engine still runs after turning key off Sign In

An engine continuing to run on after the ignition is shut of is called "dieseling" and there are 3 basic causes with #1 being the most common.


  1. idle speed too high
  2. engine too hot
  3. mixture too lean

Some GM vehicles in the 70's used an idle speed solenoid to avoid that problem.The solenoid would be energized when the key is on and act as an idle speed adjustment. When the key was shut off the solenoid would deactivate and the throttle would drop to a "below idle" position to prevent dieseling. Sometimes the solenoid would be used to increase RPM when the AC is activated.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Dec 21, 2014, 11:56 AM

Post #7 of 12 (1353 views)
Re: engine still runs after turning key off Sign In

Right on HT. I did suggest those issues common more in the 1970s. With all the intake crap now on this thing still don't know exactly what it is any controls like that idle stop solenoid to stall it when key turned to OFF is probably missing.


Having a chrome plated coil and alternator and pretty stuff for this shouldn't matter but appears all kinds of intake crap has been added without any regard for much of anything but the maker selling it no question saying it will be a total improvement in power and so on like most,


T



robster
User

Dec 21, 2014, 4:13 PM

Post #8 of 12 (1332 views)
Re: engine still runs after turning key off Sign In

is dieseling a bad thing, what are the consequences that might happen to my engine?
should i turn the idle mixture a little to the left to make it richer?
i pulled out the plugs and the color
is normal light brown no sign of oil or excess gas.

my temp gauge tho doesnt say that the engine is overheating, the needle stays in the middle or below.


Hammer Time
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Dec 21, 2014, 4:30 PM

Post #9 of 12 (1329 views)
Re: engine still runs after turning key off Sign In

No, you don't want to ignore that. What is the idle RPM? Is the timing set correctly?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



robster
User

Dec 21, 2014, 6:43 PM

Post #10 of 12 (1322 views)
Re: engine still runs after turning key off Sign In

my car doesnt have an rpm gauge, this model doesnt have one.
yes,the timing is set correctly, i bought a timing gun and i check it weekly after every long drive.


Hammer Time
Ultimate Carjunky / Moderator
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Dec 21, 2014, 6:45 PM

Post #11 of 12 (1321 views)
Re: engine still runs after turning key off Sign In

I'm betting it's an idle speed problem.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Dec 21, 2014, 10:22 PM

Post #12 of 12 (1308 views)
Re: engine still runs after turning key off Sign In

Quote from post #11 "is dieseling a bad thing"


Can be. You can end up with pocks or holes in the pistons or valve issues/damage.


Why do you need to check timing every long drive??????????????????? If it was off there's a problem.


With engine idling properly if this is dieseling put a little load on engine for shut down, use higher octane fuel or get the dashpot that it should have had new is best,


T







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