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Cylinder 1 Inactive. Clean Spark Plug


Best Answer minitalia1275 , 20 November 2015 - 12:31 PM

Sorted, changed the leads, made no difference, changed the coil and the problem resolved.
Thanks Go to the full post


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#1 minitalia1275

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Posted 15 November 2015 - 07:05 AM

1968 Mini 850. My mini is running lumpy on load. Fine at tick over but struggles to reach speed and going up hills.
All four plugs are sparking but after removing and inspecting the plugs, I noticed the the plug from cylinder 1 is clean as new, there is only clean unburnt fuel on the plug. The other 3 are all sooty. Replaced the plugs and still the same thing happening, cylinder 1 spark plug is always clean. There seems to be nothing happening in the cylinder.
I have checked the gaps, done a compression test (125 psi at all 4 cylinders). Set valve clearance 0.30. News points, new condensor. Timing done, static and strobe.
The only fault that I have found was the vacuum diaphram isn't working, considering that the distributor is almost 50 years old, I will buy a new one. The coil seems to be the only thing never changed from new (1968).
I have no idea, please help.
Thanks. Rob

Edited by minitalia1275, 15 November 2015 - 08:15 AM.


#2 David128

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Posted 15 November 2015 - 09:54 AM

Hi Rob might be worth checking the HT Leads and replacing plugs. It has been known for plugs to spark fine when tested against block then not spark when in engine.. Also check dizzy cap for tracking 



#3 minitalia1275

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Posted 15 November 2015 - 10:10 AM

Hi Rob might be worth checking the HT Leads and replacing plugs. It has been known for plugs to spark fine when tested against block then not spark when in engine.. Also check dizzy cap for tracking


Thanks David. I will try new leads. The dizzy cap is new, what do you mean by tracking?

#4 David128

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Posted 15 November 2015 - 10:32 AM

if its new should be ok. Tracking is the spark finding it's way down to earth or another cylinder, it is a carbon type build up that resembles cracks. Can be due to dirt or damp. Would be unusual in a new cap.



#5 Blatherskite

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Posted 15 November 2015 - 10:33 AM

Hi Rob might be worth checking the HT Leads and replacing plugs. It has been known for plugs to spark fine when tested against block then not spark when in engine.. Also check dizzy cap for tracking 


Failing leads are often ok when the engine isn't under load, but earth to somewhere else when it is. Try revving whilst looking under the bonnet at night without lights and see if there's any sparking visible.

#6 Wim Fournier

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Posted 15 November 2015 - 01:39 PM

It is known that in an environment 'under pressure' the spark has a harder time to spring the gap in the plug. It seeks a way out. And yes, in the drakness of night you can see a wonderfull thunderstorm taking place under the bonnet of your car.



#7 Tamworthbay

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Posted 15 November 2015 - 03:28 PM

And don't trust a part just because it's new. Quality of parts is somewhat variable these days. If you can swap the dizzy cap for a known good one then I would try that if only to rule it out.

#8 minitalia1275

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Posted 20 November 2015 - 12:31 PM   Best Answer

Sorted, changed the leads, made no difference, changed the coil and the problem resolved.
Thanks




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