Hello, brother in law here to add to the story.
I suspect something is wrong in the electrical system that is causing the voltage loss, and that in turn is stopping the ignition from generating spark. Although it's possible the voltage has been low for a while, and it still used to work anyways, and a new problem has appeared.
The voltage on the ballast even with one end unclipped is still only around 9V. Again, even right on the alternator lug, it's still just 9V, even though it's a healthy 12V in the truck at the battery.
So with the key off, the voltage at the alternator lug is healthy, but with the key on, something somewhere is consuming enough power (and likely through a bad connection) to drop 3V.
The circuit from the trunk to the test points is currently too dark and greasy to figure out.
With a test light on the coil +, it appears to "blink" from dim to brighter as the car is cranked, indicating to me that the ignition module is at least trying to toggle the coil. It just doesn't make a spark.
No spare coil was available to swap with, but coil is newish. Possible that it's healthy but just not getting enough current flow to generate a spark.
Ballast resistance was an ohm or two.
+ to - of coil was approximately 2 ohms.
+ to high voltage of coil was several K ohms.
Coil body was possibly not grounded securely, if that matters.
Any insight based on that?
