Triumph Repair: GT6 distributor/cd ignition, crane ignition, crane system

Question
1971 Gt6. Ground up restoration with 1000 miles was running great.Delco distributor W/ Crane xr7000 cd ignition. Cylinders 1 and 4 get no spark as measured with inductive timing lite. Other cylinders fire great. This has been driving me nuts for a year. I have replaced wires plugs distributor caps and rotors.Is there a way to test the Crane ignition? Should I try to go back to points and condenser? I would apreciate any help.Thanks.
Mike

Answer
Hi Mike, I don't know the Crane system but I do know it can't pick which cylinders it wants to kill. Look at the system in the dist. Is it a LED (light) system or is it a magnetic pick-up? Either way look to see if the air gap is the same on 1 & 4 as it is on the other cylinders. If it is a light system see that the disk slits are free on the 1 & 4 part of the disk. Another thing to look at is your tach. The tach is looking at the primary section of the ignition system only. So two dead cylinders (electrically)have no signal from the igniter it will make the tach needle jump at low RPM.
If all that does not net you anything, you need to find a shop that has a scope. A scope will tell you exactly where the problem is. A scope is a visual display volt meter showing amplitude (voltage) and time and can display the secondary and primary section of any ignition system. Any good man with a scope can do this so you don't need to look for a Triumph tech.
Let me know.
Howard