Symtoms were long cranking time, sometimes no start, when the engine was running it was backfiring under acceleration. With the engine off all ignition checks were normal. The external coil had been replaced before. I found the coil was not grounding good which caused a voltage drop under load. I cleaned the coil and mounting bracket good with a rotary wire brush. Now it starts instantly and idles much smoother, no more backfire.

 

Back to the basics! Good job! We all need to step back sometimes and look at the simple stuff first.

 

Good Information, thanks!