by Jimmyt » Mon Dec 03, 2018 1:31 pm
Have you already determined which cylinder isn't running (title implies this)? If so, how?
My first test in a loss of cylinder issue is an inductive timing light to check spark signal. Mine has long enough leads that I can generally reach the ignition switch while holding the light. I just hold the light trigger and hit the starter switch and look at the light to check for a pulse. I would have started it and checked each plug wire for spark - if it would run. This will only tell you that the coil, wire, ignition module might be ok, won't tell you the plug is actually sparking properly. If you're showing spark on both cylinders, you need to pull the plugs and check them for proper spark visually. At this point, you'll probably need a helper or a remote start button.
The inline spark tester from harbor freight will give you a similar result, but you have to be closer to it to see - need another person possibly. Again, this will only show that you're getting a pulse - not necessarily a spark.
No spark signal usually indicates a module, coil, or wire issue, but I'd still put a good plug on it and check before I started up the line. Plugs are probably the cheapest and easiest things to just try.
The timing light and spark tester may show a pulse even when the voltage isn't high enough to spark a good plug, so this is only the first part of the puzzle. It will tell you if something's gone totally bad, and safely determine which cylinder it is. You can pull each plug wire while the engine is running to determine which cylinder it is. I have had a really bad experience with this technique and don't use it or recommend it.
You can have a plug fail (even get a bad one out of the box), so can't rule that out because they aren't old. Swap the position of your plugs and see if it changes which cylinder is dead. Good check if you're by yourself and don't want to buy new plugs to try something. If your problem changes cylinders, you'll know it's just the plug.
Good luck, and let us know how it goes.