After reinstalling the dissy today I was fiddling with the timing and going for test drives.

Went to make some more adjustment moved the dizzy too far. It took a bit of fiddling to get it in the right spot and started again but then began having trouble with the timing light refusing to fire at low revs and couldn't get the car to idle properly even just adjusting the distributor by hand

Is it possible the coil has died or is dieing. With all the fiddling I left the ignition on at one point but I'm sure it was not for that long.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Points or electronic module?

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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.

Electronic.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

If the module dies it's toasted- no sparks at all.
OTOH coils can and do fail in funny ways, such as you have described.
Check all the HT lead resistances too unless fairly new.

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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.

Checked the HT and coil lead all good except that there was a poor connection between the coil lead and the cap so cleaned it up.

Seemed to help and drives OK but somethings not quite right. Still seems to idle rough and the damn timing light only works intermittently. Even the rpm on the t-light won't display consistently.

Is replacing the coil the next logical step? Could the fact that the timing light is not firing consistently mean there is not a decent consistent dose of volts from the coil.?

Is a GT40 the right coil for a Pertronix Ignitor module?

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Look for a loose wire or bad connection on either side of the coil. I have given up using spade lugs there, they seem to work loose. All my coil connections are now screwed on terminals.
Also check the connections inside the dizzy. A Pertronix dizzy I bought had a stripped thread where the top plate screws onto the body, it gave similar symptoms to those you describe. I fixed it with a longer screw.

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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.

Ok Cheers Doc I'll check it out.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Wires to the Dissy Module are screw on, ign wires are spades, all seemed tight, plate seems OK. Going to take it for another drive and see how it goes.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

New plugs seems to have cured issues. Timing light now working too. Looked at the old plugs and gap was too large. Must have used the wrong gauge ...note to self wear glasses

Is it possible the timing light would not fire is a spark does not occur at the plug? Maybe thats the reason the timing light was playing up.

I'd still like to test the coil. Does anyone know what the readings should be for a GT40 if I bench test it with a multimeter?

GT40 also seems to be NLA also according to Repco.

Cheers

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

With my timing light if the plug is not sparking the light won't flash.
It is handy when trying to work out which plug is not firing on a V8.

Cheers, guess that explains it. I'm still a bit suspicious of the coil. The plug gaps weren't that huge.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

GT40 has been replaced by the GT40T. It's a potted epoxy filled one, now made in PRC. They were made here, but had a poor reliability record particulaly with Mini racers.
[edit] the GT40R is now a GT40RT as per comments above.

If you want an original `oil filled' GT40 or GT40R, try Robbos Spares at Blacktown. I bough one there recently, nobody else had stock. $60 though...

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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.

Thanks. Repcos replacment offering was a $30 Fuel Miser brand coil (C80).

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Not all electronic ignitions die.... some just get ...unwell.

I've had several (in different models - from different manufacturers) that fail intermittantly.

Which is why I now run points - they either work or not.

Cheers, Ian

Phil before doing anything else, remove the dizzy cap, spray inside and out with WD40, wipe clean, spray again and refit.
Mine did this today, I found it was condensation inside the cap from all this humid weather. Was fine this morning during a short run, then started doing this when almost home.
It would start OK, rev fine in neutral, but under load would misfire.

[edit] this would also cause your timing light to be erratic.

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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.