Problem solved. Swapped the cap and rotor out and we have perfect ignition using a 12 volt source. The odd part is that it was still sparking before so maybe the spark wasnt strong enough to register before the new cap and rotor???
I have to suspect a carbon track inside the distributor cap. As I understand it, when the spark plugs are worn, or provide an unusually high resistance, the spark may arc along the inside surface of the cap. If it does this for a while, it lays down a carbon track. This might give you a situation where you have an intermittent miss that can be made better if you replace the spark plug and wire, but the carbon track is still there. The thing is that the carbon track probably won't lead to the cylinder it is supposed to. This will give you a weak spark in another cylinder, which will not have any noticeable effect since only one cylinder is ready to fire.
If the carbon track bypasses the number one cylinder spark plug wire connector, that might give you intermittent, or no spark to the No. 1 plug wire, which is the trigger for the timing light. It might just be that the spark isn't strong enough to trigger the light.
Sometimes you can clean the cap out, but why bother?
Someone once told me that all coils are 6 volt. I don't think that is true, but I do believe that most coils aren't comfortable with a steady diet of 13.8 volts, which is what healthy 12 volt alternators and generators produce.
After all these years I finally read about an extra starting circuit that increases the voltage to the coil during cranking. As mentioned above the cranking voltage will drop to 8-9 or 4-5 volts, depending on whether it is a 6 volt or 12 volt system.
Am I correct in thinking that this circuit only exists on 12 volt systems and bypasses the ballast resistor?
