Morris Minor Owners Club

Hello

Bluey has a running on problem.

When i switch off the engine it keeps running for a little bit in an unsteady manner.

What can i do to solve this.

James Stephenson

are the ignition leads the right way round

Yes i assume so as the car runs fine when going along and it idles fine albeit a bit high.

James

Timing could be a little bit too advanced but the most likely cause is carbon build up in the combustion chambers which continues to "burn" after the engine is switched off. Hotter plugs might help or the old "half gallon of diesel in a tank full trick" might help....

The fast idle is the main obvious problem - drop it down as slow as possible! I would argue retarded timing may lead to running on - but it is certainly glowing carbon that keeps the engine running. So PSLs trick with some diesel may help - although water drawn through the engine via the vacuum line to the dizzy, can also clear carbon.

bmcecosse wrote:The fast idle is the main obvious problem - drop it down as slow as possible! I would argue retarded timing may lead to running on - but it is certainly glowing carbon that keeps the engine running. So PSLs trick with some diesel may help - although water drawn through the engine via the vacuum line to the dizzy, can also clear carbon.

That reminds me of the cheapskate water injection we used as apprentices- connect the vacuum pipe via some washer tube to a squezy bottle of water sat in the drivers lap. Didn't ever do much more than splutter if you squeezed too hard The things we do when we are young!

I think i need someone to set the whole system up. Any volunteers that live nearby.

James

You could try some water in a perfume atomiser, if you have one.
Get the engine up to working temperature then remove the air cleaner and spray water into the carb with the engine running.
You might need to rev the engine a bit.

It shouldn't need much water as the effect is probably due to the temperature difference.

What you don't want to do is put too much water in and cause a hydraulic lock in the engine
Whatever you do don't try and trickle water into the inlet.

A step up from a perfume atomiser would be a sprayer like surface cleaner etc. that come in a spray bottle. Use the original stuff up, turn the adjuster to a spray pattern and replace with water then try spraying it across the carb inlet rather than directly into it.

If none of this does any good make sure you have the right heat range spark plugs fitted.
You could always do that 1st

mine did this and it was air getting in were the carb gasket had a crack in it. i found this out by spraying break cleaner on it and the engine started to die. i then changed the gasket sprayed it again and nothing happen the engine was fine and it stoped trying to tick over after i turned the engine off.

Good point hotrodder13 weak mixture=too hot as well.
Running on is a symptom of something getting too hot in the combustion chamber of the engine.
There is more than one way this can happen and that is definitely a contender.
I was horrified at the condition of one of my carb gaskets, I'd be amazed if it wasn't affecting the mixture and making the engine run hotter.

This problem is often caused by an air leak giving a weak mixture. It's also worth checking the condition of the carb needle and making sure that the jet is centred and not loose - procedure in any workshop manual.

Whilst ignition is usually blamed, my experience is that it's more likely to be carb related. Also worth checking that the manifold is secure. Has a servo been fitted, or a vacuum gauge? If so, check the hoses for air leaks. Good luck.

With the later A series engines - in the Metro - Rover had to fit an 'anti-run-on' valve to stop the engine doing just that! On switching off the ignition - the valve opened, and allowed excess air into the inlet manifold - killing the tendency to run on!

i have further retarded the ignition only to lose a little power and it still runs on. I will check the carb side of things. I have a gasket set for that carb and a new jet. I will take a look at the needle too.

May well be a holed gasket.

It could be running lean i suppose.

Does anyone live near me who could set my ignition timing and set the mixture to the correct settings next week.

James

Advance the timing till it 'pinks' under load -then retard slightly. Have you dropped the idle speed as low as it will go ?

I will try the advance thing first. I will also adjust the idle once i have advanced the ignition or should i lower the idle first.

James

Lower the idle !

Mine does that sometimes, like the engine is still trying to run. I'm not too bothered about it though, it more like a couple of coughs after I turn the ignition off. Think it's because mine is running a bit rich, could do with a tune up. I'm sure you know the ways to check if it's too rich... colour of spark plugs... rev the nuts of it and see what colour comes out the exhaust...

Of course, idle speed and mixture do connect. Adjust the idle speed, then adjust the mixture until it runs smoothly without hunting, then adjust the idle speed, then the mixture, then idle....

It's not always that bad, but if it's the first time you're doing it, don't be surprised to have to do it more than once. The engine must be hot before you make these settings. Also, if the choke is wrongly adjusted, there's a screw that also increases the idle speed for cold running. This should NOT touch the throttle cam in normal position, relying on the idle stop screw to adjust the speed. Sorry that nobody has yet come on to offer to help you "in the flesh", but hopefully someone will soon - have you joined your local branch? It's always a good source of knowledge.

Hi,

Do you have a smiths emmision valve fitted? If so, very carefully check the diaphragm for tears and splits and replace if needed. With a higher idle than normal and also running on this would possibly be the simplest first check.

Regards

Phil.