86 K20 Weak Spark

[palposity]

Hey Folks,

I need some advice. My K20 was running pretty good and all of a sudden would not start back up at the gas station after a fill up. I towed it back home with my diesel. The next morning it fired right up then died after a few seconds. I checked for spark and it seemed weak, but it was there. I put a meter on the hot wire going to the distributor and it was at 12V, but when cranking the engine it would drop to 6V or so. Is that normal? The truck will no longer start, but during cranking a cylinder or two will fire from time to time. I changed the ignition module inside the distributor, new spark plugs, I'm wondering if the coil inside the distributor cap could be drawing the current down, or would it have to be a short somewhere between the ignition switch and the distributor?

Thanks for your thoughts on the matter.