Texasmark - ,I have the same problem, what are we looking for with the timing light?
On these triples it's real hard to tell when you dropped a cylinder CDM (Capacitor Discharge Module....aka the thing that develops high voltage from a little trigger from the stator coils under the flywheel, and connects it to the spark plug), or when one is loafing on you.
The timing light is the easiest way to test for presence or absence of spark on a cylinder. Battery types are the easiest as you have the red wires from the battery and 12v distribution point handy. I have caught bad CDMs 2 out of 2 occasions and one was temp sensitive....wouldn't work cold but when engine warmed up it worked.
Just put the sensor on or near the plug wire you are interested in and pull the trigger. Watch the flashes. You want a nice steady, repeating flash, at a constant rate with all producing the same flash. Another way is to buy or build a spark tester but the timing light is easiest, but on some problems you need to know how hot the spark is and the spark tester will do that. It's just a gap, forget the dimension, to ground and you put your spark plug wire on one side of the gap and engine block (battery -.....aka ground) on the other. If it jumps a good hot, blue flame, you are good to go. Thinking somewhere around 1/4" for the gap. Check the archives.
