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distributor cap/rotor question

simon a-b

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I have had an ignition fail. Driving happily along, good response, everything happy and well in the world. 

Then a couple of pops/stutters, a minute of more running, then dead. No spark at the plugs. 


I have a 9v coil, tested and good (checked resistance of both primary and secondary windings)

I don't have the resistant wire, I have a ballast resistor instead. Voltages checked- start circuit gets battery voltage (~13v), run circuit gets ~7v

I have lumenition. 

Bulb/pickup checked and operating. I did the test with a peice of thin carboard acting as the rotor vane thing cutting the beam. When I cut the beam I got a fat, healthy spark from the coil, down the main lead (arcing across to the cam cover to test). 

I have new spiral wound leads. 

Lumenition tested as well- bridging the blue and black wires at the three-pin connector also produces spark. Spark is good. So I don't think the 7v vs 9v is the issue- unless this is what changed, and I can't see how?

One question on the resistor- it's a ceramic block with a resistant wire protected by the ceramic. The wire glows red hot when it's running. The design holds it away from anything flammable so I think this is as standard, but I'd be interested if anyone thought this was a concern?

So the only conclusion I can come to is that the failure is somewhere between where the main lead enters the distributor cap and the plugs. No spark seen at any plug lead. 

Can a distributor cap or rotor arm fail like that? It seems to be the only answer.

The rotor arm is clean and good- I gave the end a light rub with fine grit sandpaper and the central button is clean. The pickups in the cap are clean too, I gave them a quick once-over as well. The cap looks to be undamaged. 

Will any Lucas 45D 4cylinder cap fit? Is there any difference between them? I've read of the blue cap vs the black cap- it's a S3 so no turbo. 

Thanks in advance (timing pun)



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