[Offgrid]

Thanks once again for the helpful comments and advice. I forgot to mention that I had tried the "night owl" test - spin the engine in the dark, and look for blue corona lights on the cable and tracking on the distributor. There was no sign of any. It looks as if the problem is with the cap or the leads. I'll take the cap off again, and do a resistance test.

The bolts in the distributor cap are really difficult to reach. I've got a milwaukee 3/8 cordless wrench, and, if I can find it, I'm hoping that will make it easier to remove the bolts. Then I'll check the resistance between the collector pin in the cap and the central electrode in the plug.