Ignition puzzle

[Tony Griffiths]

Ignition puzzle. Drove my Seven - 1930 with a just-rebuilt 1930-31 distributor with standard points ignition - up to the garage door and switched off. Although running perfectly before and starting easily, it would not re-start - there was no spark at the plugs.
Fitted another just-built and known-to-be-working replacement distributor but, again, no spark produced.
Fitted each of the distributors to another car - and both worked.
Put the original distributor back on.
Changed the coil—no difference.
Checked the earth of each distributor—both OK
Hot wired the coil direct to the battery—no difference
Tester showed that negative lead from coil to distributor was working.
Took HT lead that comes from coil and held it against the block while cranking the engine - sparks OK
So, neither of the distributors that work on one car, won’t on the other.
Any ideas, anyone?

[Ruairidh Dunford]

Change the spark plugs.

[AustinWood]

I agree. If it's not plugs it will be fueliing.

[bob46320]

Do you get a spark at any of the plugs ? If so, Then check the timing back to TDC on number 1 -

[Alan]

Are you using the same distributor cap? If so, try it on the other car.

[Chris KC]

Tony, you already checked the HT lead from the coil to earth while cranking the engine - now do the same with a plug lead. if that sparks OK it can only be the plugs.

[Tony Griffiths]

There is no spark from the HT leads to the plug when held against the cylinder head or block, etc. Nothing at all. Everything is earthed and even hot wiring it to miss the ignition switch makes no difference. Both distributors work perfectly on another car - but not on this one. Crazy, eh! Of course, I've tried changing the distributor cap (tried three in fact) but it made no difference; each of the alternative caps also worked on the other car.
Plugs - I'll change those, just in case.

[Alan]

The plug leads, are they copper or modern plastic ones?

[Tony Griffiths]

New copper leads.

[Ruairidh Dunford]

Tony,

can you run another car with the cap and all 5 leads as they are now?