ausmini :: View topic - car won't stop

I have a quick de-carbonising method that was shown to me by a mechanic friend back in the 70's.

Get the car up to operating temperature (hotter the better) then while manually holding the revs up to about 3000 pour a thin stream of cold water into the carbie (really). It will make the car run rough but you can compensate with the throttle to keep it going. Watch the black smoke come out the back. When the cold water hits the combustion chamber it makes the carbon crack up and it goes out the exhaust. When the carbon is gone the car will stop the black smoke.

I've done this many times and it really works. You can only do it with a downdraft carbie, doesn't really work with Webers. I wouldn't try it on an alloy engine either but will be fine on a Mini engine. It will make a LOT of smoke so do it somewhere that you won't gas yourself or your neighbours.

Pete

Author:	moustache [ Thu May 07, 2009 8:10 am ]
Post subject:	car won't stop
whenever i turn off the ignition, the engine keeps going. it can go anywhere between five and maybe 20 seconds, often revving high before coming to rest. how do i go about fixing this?

Author:	Harley [ Thu May 07, 2009 8:32 am ]
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Does it run on like normal or is it really rough?

Author:	Tombo [ Thu May 07, 2009 9:17 am ]
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Does it hiss just before it stalls? If so it's turning backwards. Have you changed the plugs recently? Is the timing and points gap good? Running on is bad, try to stall it using the gears if it does it.

Author:	Blokeinamoke [ Thu May 07, 2009 9:20 am ]
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Have you decoked the head in recent history?

Author:	ddk848 [ Thu May 07, 2009 9:30 am ]
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Sounds like the engine needs de-coking or de-carbonizing? If too much carbon/soot builds up on top of the pistons it can begin to glow red hot - when you switch off the ignition the red hot carbon can supply enough heat to keep igniting the fuel (in place of the spark plug) and the engine will keep running. Eventually the engine will stop when the temperature of the soot drops or you run out of fuel (if you have an electric pump the faster revving will occur when the fuel in the float bowl runs out and the mixture leans out just before the fuel is all used up). Generally you'd need to remove the head and scrape the excess carbon off manually. But there are a few 'quick fixes' you could try: - Check and clean your spark plugs - if they are very black and sooty this could indicate that there's a lot of carbon inside. The worrying thing though is why there is such a severe buildup of carbon in the engine? If there is, the fuel you are using could be very poor quality or the car could be in desperate need of a tune up (wrong mixture, wrong spark plugs)? You could try a fuel additive and some premium unleaded to clean out some of the crap in the engine, I've used fuel doctor (you can buy it at supercheap - http://www.fueldoctors.com.au/) Driving short distances where the engine doesn't have time to warm up properly and you use the choke a lot will definitely cause more buildup. Another thing you could try is the 'Italian tune up' - once you've put in the additive and some good fuel, warm the car up and then drive it at high speed/high revs up a hill - hopefully this will burn some of the excess soot off and send it out the exhaust - but at the end of the day it is far from the 'correct' method of dealing with this problem. Probably best to have your mechanic take a good look over the fuel and ignition systems. Hope this helps! (Any other members please correct me if I have any of this wrong).

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Author:	Timbo [ Thu May 07, 2009 10:12 am ]
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As you turn off the ignition, floor the accelerator, it will stop much quicker. Tim

Author:	peterw [ Thu May 07, 2009 10:48 am ]
Post subject:
I have a quick de-carbonising method that was shown to me by a mechanic friend back in the 70's. Get the car up to operating temperature (hotter the better) then while manually holding the revs up to about 3000 pour a thin stream of cold water into the carbie (really). It will make the car run rough but you can compensate with the throttle to keep it going. Watch the black smoke come out the back. When the cold water hits the combustion chamber it makes the carbon crack up and it goes out the exhaust. When the carbon is gone the car will stop the black smoke. I've done this many times and it really works. You can only do it with a downdraft carbie, doesn't really work with Webers. I wouldn't try it on an alloy engine either but will be fine on a Mini engine. It will make a LOT of smoke so do it somewhere that you won't gas yourself or your neighbours. Pete

Author:	TheMiniMan [ Thu May 07, 2009 11:08 am ]
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Maybe just lower the idle adjustment on the carby so it idles lower yeah?

Author:	drmini in aust [ Thu May 07, 2009 11:41 am ]
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Sounds like the C/R is about right then if it's doing that.

Author:	Drexxle [ Thu May 07, 2009 12:36 pm ]
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Quote: Does it hiss just before it stalls? If so it's turning backwards. Not backwards, just retarded. And if checking with a timing light, and its correct, then play in the distributor.

Author:	superSeven [ Thu May 07, 2009 3:27 pm ]
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i found running on high octane (bp ultimate, mobil 8000 etc) stopped my car from running on.

Author:	sgc [ Thu May 07, 2009 3:42 pm ]
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My CR is on the high side and I have always had trouble with the motor wanting to run on a little. I've always stalled it on the clutch as I turn off the ignition, I do it without thinking now. I did find that (oddly) going to a spark plug one range hotter reduced the run-on tendency a little -- I think this is because they run hotter there's less carbon build-up on the plugs, which in turn reduces the opportunity for ignition due to glowing deposits. Or not, I could just be imagining it

Author:	drmini in aust [ Thu May 07, 2009 3:48 pm ]
Post subject:
sgc wrote: My CR is on the high side and I have always had trouble with the motor wanting to run on a little. I've always stalled it on the clutch as I turn off the ignition, I do it without thinking now. I did find that (oddly) going to a spark plug one range hotter reduced the run-on tendency a little -- I think this is because they run hotter there's less carbon build-up on the plugs, which in turn reduces the opportunity for ignition due to glowing deposits. Or not, I could just be imagining it If the motor is built for power, has a decent 270° or bigger cam, and the C/R is around 10.5 or more (which it should be), yes you will probably have this problem, it comes with the territory. I use the sgc method too, always have. Some later A series overseas were fitted with a `gulp' valve, which opened the inlet manifold to atmosphere as the ignition turned off. That stopped it...

Author:	michaelb [ Thu May 07, 2009 6:19 pm ]
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All of the above suggestions are good and quite normal for a mini with slightly higher CR ratio. I always used premium unleaded and leave the car in gear when turning off the key, this reduces or stops the problem.

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Author:	850man [ Thu May 07, 2009 6:46 pm ]
Post subject:
peterw wrote: I have a quick de-carbonising method that was shown to me by a mechanic friend back in the 70's. Get the car up to operating temperature (hotter the better) then while manually holding the revs up to about 3000 pour a thin stream of cold water into the carbie (really). It will make the car run rough but you can compensate with the throttle to keep it going. Watch the black smoke come out the back. When the cold water hits the combustion chamber it makes the carbon crack up and it goes out the exhaust. When the carbon is gone the car will stop the black smoke. I've done this many times and it really works. You can only do it with a downdraft carbie, doesn't really work with Webers. I wouldn't try it on an alloy engine either but will be fine on a Mini engine. It will make a LOT of smoke so do it somewhere that you won't gas yourself or your neighbours. Pete I have been doing this for years, it was shown to me by an old mechanic and it works very well. A simular effect is had when a engine has a blown head gasket and coolent is getting into the cylinder.