Odd one off starting problem - 3.4

[healey120]

I have a 3.4 MOD that has run well for the last 5 years with rare starting issues - only occasionally reluctant to go in that period just after the cold start device has kicked out. Took it for a 30 minute run yesterday with no issues. Stopped the engine and went to put it in the garage ten minutes later and the engine cranked but didn't fire once despite repeated attempts. The strange thing is that the engine was cranking very fast, almost as if the plugs were out and no compression. After a few minutes, the engine fired with a huge chuff and stutter, a plume of gases appeared in the engine compartment from what looked like the air cleaner inlet and then it settled into a completely normal idle.
I've run the car again, restarted it repeatedly and it hasn't re-occurred.
All good, but these things don't happen without a reason and a non-start is the ultimate event in undermining your confidence in the car, especially when it's being used for my daughter's wedding in a few months!
Anyone come across anything like this before? I've seen a lot of discussion about coil performance deterioration when hot... maybe it's the start of something.

[3.8etypephil]

There are a few possibilities, including a defective coil, defective condenser (if still fitted with electro mechanical ignition), defective ignition switch, poor connections in the ignition circuit, the cold start device operating when it's not required, fuel vaporisation, sticking carburretor float causing flooding. Any of these can give intermittent trouble, but if the coil is the original, or a Chinese replacement, it would be a good place to start; they're quite inexpensive.

[3.8etypephil]

Deleted duplicate.

[healey120]

Thanks
The coil is a Lucas Gold and about four years old so not a poor copy. Since it's not too much money, I'll switch it and put in a red rotor arm, condenser, check points etc. (it's a conventional breaker ignition system). Unfortunately, I had no time to do an ignition spark check since the engine started again before I could run through the usual diagnostics and I don't like parts changing as a solution without knowing the root cause.
No fuel smell or SU fuel pump clicking so I don't think it could be a stuck float.
Over the years with other cars, I've had to cope with diagnosing no starts and it's almost always the ignition system.
What I've never encountered is the strange high speed cranking with no firing and then a sudden chuff and stuttering back into life with smoky mixture coming out of the air cleaner and then running perfectly. I hate intermittent faults since they are so hard to diagnose!

[3.8etypephil]

Agree on the intermittent faults being a pain (They either stop recurring, leaving you wondering "Will it leave me stranded today?", or lull you into a false sense of security, biting only when it really matters, such as when providing daughter's wedding transport.), and on such problems almost invariably being the ignition.
I recently spent a few hours helping the OP of:

viewtopic.php?f=303&t=14441&sid=7b33730 ... 4&start=15

It turned out to be a few poor electrical connections, incorrectly fitted AED, and a defective coil which was supposedly changed by a well known Jaguar specialist a couple of years ago. Remarkably it seemed to have 1974 dirt and rust on it.