been trying to figure out why my blazer is running the way it is, read alot of threads. so I tried one thing I had read and have a question bout it. it was about pulling plug wires off one at a time. So I pull #1 off and start it. Ran exactly the same, put it back on and pulled #3 off (from the cap) started it, Ran pretty much the same but the terminal on the cap was sparking, it didnt spark when I pulled #1. That's as far as I got, should I continue or get a new cap and rotor and try again? BTW I set the timing Using #1 odviosly, and the light flashed but it did have sort of an irregular faint flash about every other blink in between blinks. and the cap and rotor don't look bad at all. what do ya think?

 

The cap should not spark at all if there is nowhere for the spark to jump to when the wires are off it. Is it jumping from the electrode into another plug wire?

If you unplug your fuel pump relay by the brake booster you can crank the engine over without it starting to get a good look at the spark, it also helps to do it in the dark.

Remove your cap and see what the electrodes look like in the cap and on the rotor tip and center. They should be shiney and have a little black dust looking stuff on them. If they are all burned then its time for a new one. You can also sand off that burned stuff and try it again, but a cap and rotor are cheap parts.

While you have the cap and rotor off, wiggle the distributor shaft, there should be ZERO play in the shaft side to side.... If there is any play, find a new distributor at the junk yard. If your distributor wiggles a little it makes the rotor not make a good contact with the cap pins as it rotates past them, resulting in poor or no spark going down the lines.

If you are getting a flash in between flashes then that could be from the spark jumping to another wire due to bad plug wires themselves. Unhook your pump relay so the engine wont start and it will slow down the timing process for you to see better.