One simple diagnostic. Turn the ignition on, don't try to start, can you hear the fuel pump run for a few seconds. If you can it means that the fuel pump and relay are good.
As the engine was running before you turned the ignition off, it suggests that there is something affected by the heat that no longer works under the lower voltage present while cranking the engine.
One item not mentioned so far is the pickup in the distributor. I suffered for a long time with an occasional failure to start. Tried all of the items listed already. Eventually, while down in Cornwall with a failure to start, I checked the gap between the sensor and the toothed rotor. Just used a piece of very thin card to judge the gap. Not sure if it was the effect of the card cleaning the edge of the sensor, or me closing the gap, but problem was cured. As your engine was running before you turned the ignition off I guess the sensor (pickup) coil is OK (no breaks) otherwise you would have experience running issues, could be the output signal from the sensor is too low for the ignition amp when cranking the engine.
The one item that has caused me most issues is the rotor arm, just had to change one again, the quality of new ignition parts is a bit of a lottery, have even had one that wouldn't fit on the distributor shaft, and a cap that wouldn't sit on the distributor.
Thanks Mike
Fuel pump and relay are fine, as you suggest something does not like the heat. I’ve put my spare new coil on and will test it this week, I’ve also ordered a fuel temp sensor from the UK, so unlikely to see that until the end of the week. I’m now trying to find a stepper motor that isn’t Britpart…
