I just had the strangest think happen to my 1986 I6, and I would like to figure out why so wnen I am miles away from a warm bed I can fix it, again.
I rebuilt my I6 last year with new almost everything. It has theTFI GM module, coil, with the vacuum dizzy. I don't drive it daily, it my bike/camp gear rig. So I go to start it and it cranks but does not fire. It usually expodes to life. The only "out of ordanary" problem I had as of late is the safety switch that is connected to the clutch arm. The one that maks you push in the clutch before the motor cranks over. The switch trigger is getting worn so I had to really push the pedal to the metal, which kind of gave a strange pop sound. I slid the trigger back inplace.
With no tools on hand, I pulled a spark plug and placed a key in the wire boot and cranked the motor trying to find ground and a spark. No spark. Same with coil wire. Time to get some tools.
I thought I might have blown a fuse but I checked them all.
I had 10v to the coil and 12v coming out of the coil.
So then I am looking at the Dizzy cap. I pulled it off and the contact posts look flakey, but i seen worse, so I clean them all off with my pocket knife including the rotor cap contact.
I put things back in place and it fired right up. WTF?
Maybe it's just that time of year when rust never sleeps?
Am I missing anything?

 

Somebody needs a spell checker. I used the van today. Started right up every time. Went to the lumber yard, moved the van around, so I must have started it about 6-8 times with no trouble. DAMNIFIKNOW why it would not start last night. It was sitting in a dry garage too!

 

Check ignition module or just upgrade it. Some early to mid 80's ignition modules were exceptionally bad.