engine tends to ''run on''

[Bob Claydon]

Hi The engine,on my 1969 Minor 1000,when warm tends to ''run on'' when the ignition is switched off.My limited knowledge tells me it is something to do with the timing.Any ideas? Many thanks.Bob Claydon.

[bmcecosse]

Could be - common problem. It's caused by something glowing red in the chamber and igniting the mixture even though the sparks have been switched off. Drop the idle speed, reset the idle mixture and advance the timing till he hear some pinking - then retard it slightly so it's not quite pinking. A change of petrol brand may help too.

[simmitc]

Also check for air leaks, a weak mixture causes hot running which causes running on. I once had a car with a pin-hole in the manifold and always ran on. It was only after changing engines and finding the same fault that I realised it had to be the manifold - had already changed everything else!

[C6Dave]

If the above tips don't work, then you may need to take the cylinder head off and 'de coke' the engine.

Carbon build up on top of the pistons and around the valves on the head can cause it.

[bmcecosse]

De-coking went out with the gas lights....... No need for that these days! If worried - just run some water through the hot engine at a good fast idle - that will clear it. If the engine is running too rich (maybe blocked air filter?) then correcting that will remove any excess carbon.

[dalebrignall]

how do you do that roy , i thaught water was not compressiable ,a friend of mine wrote off a brand new car by going through a ford that was too deep and sucked up a load of water and put a conrod through the block

[bmcecosse]

Not THAT much water Best way is to use the little vacuum pipe - disconnect it from the dizzy end and dip the tube end in a jar of water....... Engine must be hot and running at a good fast idle - but don't use the choke to do that - just screw down the idle screw, and set it back afterwards. Probably best to take the car out for a decent run immediately after doing the water treatment.

[aupickup]

or maybe not try it

[bmcecosse]

It does strip out excess carbon - and a lot less smoky than the old trick of running RedeX through the engine which I was never convinced about!

[ASL642]

Don't stand behind this when it emits that carbon!

[chickenjohn]

Don't put water in your engine!!! I doubt it would work as coke and ash are not soluble in water.

De-coking certainly has not "gone out with the gas light" !

If your car has been driven excessively slowly in the past, and never been at 60mph then it may very well need a de-coke. My traveller had one old lady owner before me and soon after buying a de-coke was needed to stop the running on.

Eliminate all other causes first before removing the cylinder head and cleaning it up. BTW, while the head is off, it is a good idea to inspect and clean everything and grind the valves in as well.

[chickenjohn]

how do you do that roy , i thaught water was not compressiable ,a friend of mine wrote off a brand new car by going through a ford that was too deep and sucked up a load of water and put a conrod through the block

exactly! Whether it works or not, it is dangerous advice!!!!!

[bmcecosse]

It works just fine - often used by the Mini lads. Oh yee of little faith. Much easier than head off ! If you have ever taken a head off where there has been a little water leak into the combustion chamber - that chamber and piston shows up SPOTLESS. Water injection is of course standard on pressure charged engines to both cool the charge and suppress detonation. Here we are talking about dribbling a jam jar full of water through the engine at fast idle - followed by a blast up the Bypass. It works.

[Neil MG]

Just so BMC is not on an island here - this is a tried and tested way of cleaning the combustion chambers. Yes, there are lots of ways you could screw it up, but, with an air of caution, it is perfectly safe.

Don't stand behind this when it emits that carbon!

Unless you have very, very long arms!

[MarkyB]

A very small amount of water will do the trick, a water mist blown across the mouth of the carb from one of those pump action cleaner dispensers should be plenty.

I doubt it would work as coke and ash are not soluble in water

It's more like steam cleaning than washing. Oil isn't water soluble either.

[Bob Claydon]

Hi Thanks for your advice.My local garage freed off the jammed ''nurl'' adjustment on the distributor and suggested I keep clicking towards the retard direction until the pincking stops,but how far can I retard the ignition before I do damage?

[bmcecosse]

You didn't mention pinking earlier - thought it was 'running on' that was the problem ?????? To eliminate the running on you should do the water treatment - and then advance the timing until you do get pinking, then retard slightly so it's 'not quite' pinking.