Hi guys!

I'm having problems with cylinder 3 not firing. There is spark at the plug, I'm getting compression and fuel in to it, but no luck. I did notice that the plug is getting quite oily pretty quickly, so I was thinking a ring has blown? But the compression feels the same as the other cylinders. Maybe a valve stem seal? Seems the oil is suppressing the spark. I would have thought that a damaged seal would affect the compression. I'm only doing the thumb test though, they feel the same but I don't know for sure.

Any thoughts would be appreciated! I'm supposed to be on my way home.

Cheers all!

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78 Leyland Mini - Prince

Dead spark plug, stuck valve?

Doogie

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I won Hay once, here's the pic to prove it..


Hay, it's not about the car, it's not about the venue, it's about the people that come here. Peter Dwyer, Mayor of Hay NSW.

It's weird, when I have the plug (tried a few different ones) against the head stud it sparks (both in the gap and against the stud), but when it is in the cylinder it's not sparking. The car seems to be accelerating quite well, but when the plug is in the cylinder and I remove the lea there is no change to the engine

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78 Leyland Mini - Prince

That's normal when the spark is dull. The voltage required to jump the gap is proportional to the pressure (air density) within the cylinder. If it only just works outside, then it will have trouble inside like you have found.

Time for an electrical service.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Makes sense, cheers! I'll pull the points out and shine them up, see if that makes a difference. You don't think the oil fouling is dulling the spark?

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78 Leyland Mini - Prince

A dirty plug will give the spark easier options to jump the gap, like go around the long way down the insulator and across to the shell. But it might be the cart leading the horse. It might just be dirty because the spark is not igniting the mixture. Clean the plug up with a wire brush and petrol and try again.

Once it is going, do you notice that the spark just breaks down under acceleration?

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Points? There's your problem.
Fit a real ignition and it will burn the oil off the plugs!

A real ignition is on the list for when I can put some serious time and effort in to this car. Will be great! In the meantime, points will have to do.

Mick, I got at the plugs with a file and shined them up, but to no avail. I'll get it home and figure something out from there.

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78 Leyland Mini - Prince

It's definitely firing on three once it gets going, it is accelerating ok and keeping speed, but I can hear that it's missing. It's also running warmer than this morning (when it was running very well!)

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78 Leyland Mini - Prince

Get a meter and check resistance of your plug leads, and the coil lead.
Over 5K ohms and I would bin them.
Cheap ones are just carbon impregnated string inside, the resistance increases with age and eventually they just don't work properly.

If buying new leads try and get inductive core ones. eg Bosch, or Russell Engineering's.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.