[save_old_iron]

Kerry,

when you are taking the voltage measurements,

where do you have the ground lead for the voltmeter ?

From what you have written, my guess is there is (significant) additional resistance in the start wiring to the coil that does not exist in the run circuit wiring to the coil. The resistance of the ignition switch contacts can be measured or you can measure the voltage drop across the B to S terminals to see if that's where the extra 3 volts is being dropped while you perform your spark tests.

Another thought. Instead of measuring the coil voltage during the start test, perform your start test but measure the battery voltage directly across the battery terminals. Maybe you have a sulphated battery that drops voltage during the start testing.

Is the engine cranking over when you are measuring the 9 volts at the coil ?

p.s I seriously doubt the "standard non-metalic conductors" are the issue here with voltage drop to the coil. But that said, to check if they have any influence on what you are doing, lift the leads out of the coil and try the voltage measurements again.