Gordon
Yes, if you can pick the exact moment to release the key from cranking the engine it will start and run ok. When it is stone cold, this is very difficult and I have had to resort to the old trick of warming the plugs in an oven then I can just about get it to catch.
'er indoors has done the Sainsbury's run in it today but it took me about half an hour to get it started from cold.
Once the thing is warm, it will start easily but again, only once you release the key from the cranking position. I assumed that this was because the timing of the key release was less critical because the engine was warm.
It was this behaviour that led me to believe that the problem was in the ignition switch itself. My conclusion, rightly or wrongly, was that the coil was being robbed of voltage when the key was in the cranking position. It was this that took me down the road of measuring the voltages at the coil +ve terminal where, perhaps stupidly, I expected to see 12volts.
In fact, as mentioned, I saw 9 volts with ignition on and points closed, 12 volts with ignition on and points open, and 7 to 7.5 volts cranking.
Just to throw in a couple more red herrings, the loom has clearly been "heavily modified" (buggered about with!) by previous owners.
I have the relevant Haynes manual but despite comparing the wiring with all of the various years & models wiring diagrams in the book I can't find a match. According to Haynes I should have a white lead (non ballast resistor) or a white/yellow & white/pink (ballast resistor) to the coil +ve terminal. I have a single red wire.
I wonder if, longer term, I should consider a new loom.
Also, the the solenoid is the good old fashioned type with a starter button between the two terminals. It doesn't make any difference whether I use the key or the solenoid button, coil +ve voltages are the same. I assumed that this was another indication that the Ignition switch was OK.
According to Haynes, apart from the main battery & starter motor feeds I should have a white/red (Alternator), 2 browns (fuse box & ignition switch) and a brown/blue (Alternator) connected to the solenoid. I only have 2 browns and so far I have failed to establish where they go. They disappear into the loom tape so I can't follow them by sight and testing continuity is inconclusive/confusing.
I should never have succumbed to 'er indoors desire to relive her youth by buying her a mini
I should be working on the racers.
Thanks for reading these ramblings and offering help.
