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Car runs on when ignition is off


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#1 Timwell

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Posted 08 August 2009 - 03:39 PM

Hey guys, been keeping an eye on this forum for months but only till now have had the need to speak out.

Everytime I turn the car off the car runs on for about 10 seconds.

It has SUs, electronic ignition and the timing is correct.

Could it be the coil that is shorted?

I initially thought it could be the timing but that isn't the case.

Any help apreciated.

Thanks,

Tim

#2 aegean

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Posted 08 August 2009 - 04:01 PM

Sounds more a case of pre-ignition, caused by excessive carbon on the heads. Might be time for a de-coke. You could try running some ATF (auto transmission fluid) through the fuel for a few weeks - about 1lt per tank full, and that may clear it after a few weeks. You will need to have some new fuel filters on hand though as it will clean out the entire fuel system.

Another option is to pout water SLOWLY down the carbie while it is running abd try and burn it off.

#3 xa1973

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Posted 08 August 2009 - 04:14 PM

Sounds more a case of pre-ignition, caused by excessive carbon on the heads. Might be time for a de-coke. You could try running some ATF (auto transmission fluid) through the fuel for a few weeks - about 1lt per tank full, and that may clear it after a few weeks. You will need to have some new fuel filters on hand though as it will clean out the entire fuel system.



Aegean

Out of curiosity..where did you pick up this trick....

#4 Timwell

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Posted 08 August 2009 - 05:55 PM

Wow, they are some novel ideas.... had a slight feeling that it may be preignition however there is no knocking (as far as I know).

We'll I'll give it a go and see how it goes.

Ill try the ATF method first.

Any other ideas??
Does it sound like an ignition problem?

Thanks for the help so far

#5 Zedman240®

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Posted 08 August 2009 - 05:58 PM

Have you noticed if the engine runs backwards when it happens? Way to check is, when it does it, stall it in gear and see which way the car jumps. If it lurches forward in first, or backwards still in first. I had a 910 Bluebird that ran backwards, when stalled in first, it would jump backwards. Problem solved when I backed the timing off a couple of degrees.

#6 Timwell

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Posted 08 August 2009 - 06:12 PM

Actually,

now you mentioned it.....yes it does run backwards when shut down!!

Ok so Ill change it a few Degrees tomorrow.

So what should I set it to at Idle?
It is currently set to 10 degrees, however this is the "factory" correct setting. Doesn't chaning the timing jjst mask an issue that requires rectification?

Will this then stop the run on??

Every solution produces more questions...sorry.

Tim




#7 Zedman240®

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Posted 08 August 2009 - 06:41 PM

Back when we had good fuel with a nice octane rating, 10' was fine. But with today's $hitty fuels, you have to back off timing a tad. Or if you can score some avgas from an local airport like we used to, that could help also.

#8 Timwell

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Posted 08 August 2009 - 08:25 PM

hmmm I do have connections..........

Thanks,

Tim

P.S:

Ill post when its all done.

#9 Timwell

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Posted 09 August 2009 - 01:11 PM

Well it still runs on with the timing backed to 8 Degrees,

Will now pull the plugs to see if there is any evidence there.

Tim

#10 waxhead

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Posted 09 August 2009 - 01:41 PM

Whats the idle set to
if the idle is to high this will cause this as well
You could try a heat range colder in the plugs as well

#11 aegean

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Posted 09 August 2009 - 02:50 PM


Aegean

Out of curiosity..where did you pick up this trick....


This has been something used for many years by Mercedes owners with high compression/output engines - such as the 6.3, 6.9, etc. I have a few of them, and believe me, it works. You also don't need to use new oil - any old ATF that has been filtered is fine. It is especially good in fuel injected engines as it cleans the injectors as it goes. Also good for cars that don't get a lot of use as it cleans out the varnish that forms on the fuel lines - and that is why I said you need to have new filters on hand.

#12 xa1973

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Posted 09 August 2009 - 03:06 PM



Aegean

Thanks for your reply...Ill remember that one... ;)

#13 NZeder

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Posted 09 August 2009 - 04:03 PM

With regards to the timing - I know you have said you have checked the time and set to the factory settings but did you check the balancer is not gone ie the bonding of the outer rings had failed and the ring has moved and thus your timing marks are not correct so even though you have knocked it back 2 degrees it could still be off if the rings has moved.

#14 Timwell

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Posted 09 August 2009 - 05:25 PM

Ok all good advice, Ill TDC physicaly. The plugs are carboned too.

The secondry winding in the coil isnt reading the correct ohmage either.

The primary seems fine.

Ill change the coil. Check TDC and then........repost.

Regards,

Tim

#15 Timwell

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Posted 23 August 2009 - 10:03 AM

All done,

Coil changed, TDC checked physically, its now at 5 degrees. incidently the vacume advance isnt working so ill get a new one.

Am currently running the equivilent of ATF through the system, just a little scared about what ATF will do to the carbies.

I spoke with Stewart Wilkins and he reckons I should just wind the idle right back...so Ill do that today.

If this doesn't work ill try the ATF.

thanks,

Tim

#16 waxhead

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Posted 23 August 2009 - 10:05 AM

Thats a great idea
Im suprised no one suggested it before

#17 aegean

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Posted 24 August 2009 - 03:39 PM

ATF won't hurt your carbies - or anything else, but it will clean the varnish out, so that's why I said to have filters on hand. Vacuum advance only affects the idle speed and at low revs so that isn't going to change too much, but still better to replace it. Look for vacuum leaks at the same time. All will effect the timing and tuning.

#18 Scoota G

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Posted 30 October 2009 - 04:28 PM

Does the car have Thermo Fans?


#19 mayhem

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Posted 01 November 2009 - 10:53 PM

is it electronic dizzy? this happens a lot with electronic dizzy been amped up the alt is feeding the ignition system causing run on ..... let me know ive fixed this alot with customers

#20 Timwell

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Posted 06 November 2009 - 09:26 AM

OK,

long time since posts, I have been away a bit.

I have replaced all elec parts, rotor, plugs, leads dizzy cap and plugs.
In addition I have run decoke through the car. The timing is set and the idle is wound back.

It has made a big difference but still does it occasionaly. I think the "carbon in the cylinder hypothisys is correct".

Great advise from all, I am very appreciative but it looks like I will pull the head off and give it a clean up......gives me something to do at least.


And yes it is an elec dizzy.






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