Although the coil passes the tests you have done they really aren't sufficient tests. Unfortunately further testing really requires more equipment.

I wish I could just turn up to everyone with my equipment.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

Irregular misfiring showing on timing light can indicate a dirty spark plug insulator.

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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.

What further equipment and tests do you do?

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Cheers Dave.

I use my engine analyser (Allen DEA). There are a lot of tests which can be done with it, coil defects can even show up on the primary side. As well as showing the scope patterns the kV readout is used to determine if the coil can output the required voltage under load. If you have access to a regular oscilloscope of some kind they can be made to do some of these tests. There are some old automotive meters that can read the kV.

I do also have a 1950s ignition coil tester that I need to fix.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

I wondered if you were refering to an engine analyser. I can do most tests (but not all) using a scope but I need to make some capacitive pick ups which is a project that has been on the back burner for a while. I could do a primary current ramp test.
However I have swapped out the coil and coil lead and the fault remains. So onwards and upwards.

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Cheers Dave.

The scope patterns can diagnose the fuel system and valves too.

Onto solving the issue. Is it points or electronic ignition?

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

It has an electronic module, powerspark, in an original 43d. Plenty of silicone grease to heatsink.
But regardless that is my next port of call, cap rotor and leads along with the advance weights and mech.
And for the sake of completeness I will do a compression test and check the valve clearances
I have no desire to go back to points but I will to prove a point.
But that is for another day, it is now beer oclock.

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Cheers Dave.

The problem is solved.
It was the powerspark electronic module going south.
So if anyone wants to buy a slightly used electronic ignition module, I have one here. Sold as is.

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Cheers Dave.

How much use did it get and how old is it?

Powerspark products seem to be well recommended however I have had one of their coils fail. On TMF I was recommended their coils as well as distributors, that was after their coil had already failed on me.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

I had the module for a while before I fitted it. It was on perhaps 2 years but it is a club plate car so it has not had much use in reality.
this was a red module, I have also had the earlier blue modules fail.

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Cheers Dave.

So the powerspark module was the fault which was fixed by removing it and fitting a points setup but it gave me a loss of power somewhat and a lack of response.
I have fitted an electronic ignition which I built years ago that uses the points as a trigger and has dwell control which has restored the power and response.

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Cheers Dave.

Something to play with is reducing the points spring pressure. It makes the points last a lot longer since with this type of use the most wear is from the cam.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

won't they bounce at higher RPM?

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did I tell you that I won a trophy?

I had thought about this too but I know that people do it. I just reread one of the things that I have read suggesting it. What they say is to lower the points gap to the minimum first. Then the pressure can be reduced.

Here is one site with interesting information: https://gofastforless.com/

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

That does have some interesting stuff - good find

I like his explanation of ignition, he seems to think about it the same way I do, but he has a better understanding of how each part does its little job, or at least he's better at explaining it than me. His stuff about distributors has even given me a few things to consider on my car, and I don't even have a distributor!

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did I tell you that I won a trophy?