21 replies to this topic

[GermanMoreno]

My engine tends to sometimes run on when i turn it off. After setting timing and tuning the mixture it still does it.
I am wondering if the sparkplugs can cause this. 1275 Carb Cooper and I am running BPR6ES. I am wondering if I should go for BP7ES as its stated its a colder plug.

The car runs on only when using 91 octane fuel (95RON). If I use 94 Octane it doesn't happen, but it contains ethanol! dilemma!

Any advice appreciated :)

[Maccmike8]

I dont have a problem with the ethanol.

[cal844]

It's either timing or too rich fuel. My Sprite used to do this, I leaned the mixture slightly over time and now it's cured.

You may also need to alter the timing a degree or two but only do one small adjustment at a time

Edited by cal844, 05 July 2022 - 03:40 PM.

[Spider]

There is a variety of causes for this;-

Ignition timing
Spark Plugs
Mixture (including a manifold leak)
(Very) Hot Spots in the combustion chambers
CR too high
Fuel
Heavy 'Coking' of the combustion chambers (rare these days)

 

to name a few.

Try colder plugs, but if they start fouling, you need to look for other issues.

[timmy850]

A high idle speed can also be a factor

Changing the spark plugs is a cheap and easy thing to check, although watch out for fouling like Spider says

[MiniMadRacer]

The MG Metro and some other "sporty" variants had Anti Run on valves, as this was a known issue with some tuned versions in the 80s.

[GermanMoreno]

There is a variety of causes for this;-

Ignition timing
Spark Plugs
Mixture (including a manifold leak)
(Very) Hot Spots in the combustion chambers
CR too high
Fuel
Heavy 'Coking' of the combustion chambers (rare these days)

 

to name a few.

Try colder plugs, but if they start fouling, you need to look for other issues.

 

Thanks for your answer, Ive been fiddling around with timing, I retarded it and it improved a tad although with a slight loss of power. I had to use higher octane fuel though. I need to check if the anti-run on valve works properly also but I am unsure how to do that. 

Other thing I can say is that at high revs, I can hear some air suction, I believe its from the carb which should be normal thing? 

Ill investigate further and bring updates!

[gazza82]

I dont have a problem with the ethanol.

Ah but is it the same percentage in Canada as here in the UK? Some countries run very high percentages of ethanol in their fuel.

[timmy850]

If you read the first post, he says he doesn’t have an issue when using 94 octane with ethanol.

He has the run on issue when using 91 without ethanol

[sonscar]

Ethanol lowers the burn temperature.Retarding the ignition raises the cylinder temperature.I would tune for one fuel and stick to it.The Mini is not intelligent enough to adjust itself for the difference.Spider has outlined the major causes but as mentioned some elderly motors just do it.
My memory of run on valves is that they either shut off the fuel or let excess air into the intake by means of an ignition controlled solenoid.,Steve..

[Maccmike8]

 

I dont have a problem with the ethanol.

Ah but is it the same percentage in Canada as here in the UK? Some countries run very high percentages of ethanol in their fuel.

 

 

That I dont know.

A lot of people dont want to put the new uk fuel with ethanol in it, in their Minis, my statement was more; Im happy to use this fuel. This might not have been helpful to your post so apologies.

What percentage is it it in Canada?

[GermanMoreno]

 

I dont have a problem with the ethanol.

Ah but is it the same percentage in Canada as here in the UK? Some countries run very high percentages of ethanol in their fuel.

 

Its up to 10% for the 94 Octane

[GermanMoreno]

Perhaps I should just fit the HIF44 with some ethanol resistant components. Car runs great on 94 my only concern is the ethanol. Plus replace the fuel hoses. 

[Tornado99]

My '88 Mini, single HS4 carb, 1275 cc, also does a bit of a run on occasionally. I ran some Seafoam into the air intake as per instructions on the can. Seemed to reduce the run frequency for a number of months. I only run ethanol free 91 octane (Chevron brand here in BC Canada). This would indicate some amount of carbon build up in the combustion chambers as a likely cause...cleaning it up with the Seafoam helps for a while. 

[GermanMoreno]

My '88 Mini, single HS4 carb, 1275 cc, also does a bit of a run on occasionally. I ran some Seafoam into the air intake as per instructions on the can. Seemed to reduce the run frequency for a number of months. I only run ethanol free 91 octane (Chevron brand here in BC Canada). This would indicate some amount of carbon build up in the combustion chambers as a likely cause...cleaning it up with the Seafoam helps for a while. 

 

I didnt know this product, I will look into it! although perhaps it would be just a better solution to remove the cylinder head and clean it. I dont know what it involves though. How many hours of work would this be?