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I very much needed help concerning a problem with the ignition system in my plane when I did a coil check. The plane is a Zodiac CH601XL. It has a Jabiru 3300 engine.
The problem is as follows:
• The engine runs fairly smoothly when the ignition switch is set to both (B). At this setting neither of the ignition coils is grounded. Note that grounding of a coil renders it inoperative.
• The engine runs smoothly when the ignition switch is set to right (R). At this setting the left (L) ignition coil is grounded, rendering it inoperative
• The engine dies when the ignition switch is set to L. At this setting the R coil is grounded, rendering it inoperative.
In the text that follows I refer to the ignition system as having two major subsystems. First, there is the ignition coil. Second there is a distribution system consisting of (a) a distributor cap, (b) a rotor, (c) spark plug wires, and (d) spark plugs.
Here is what I and three A&Ps with combined experience of about 60 years have done thus far:
• To determine what part of the L ignition subsystem is producing the problem, we did the following:
o Connected the high tension (HT) lead from the R coil to the L distributor. Since the engine runs normally on the R ignition subsystem we know that the R coil and R distribution system are functioning normally. So, if the engine runs normally with the R coil connected to the L distribution system, the L distribution system has to be good. With this setup the engine ran normally.
o Connected the HT lead from the L coil to the R distributor. Since the engine runs normally on the R ignition subsystem we know that the R coil is functioning normally as is the R distribution system. With this setup the engine died, suggesting that the L coil is faulty.
• I then ordered a new ignition coil from Arion Aircraft and installed it. The gap between the coil and the magnets on the flywheel was set at .010”, i.e., the recommended setting in the engine manual. I also connected the HT leads to their appropriate distributors, i.e., the HT lead from the L coil to the L distributor and the HT lead from the R coil to the R distributor. I then started the engine.
o The engine ran fairly smoothly when the ignition switch was set to both (B). At this setting neither of the ignition coils was grounded.
o The engine ran very smoothly when the ignition switch was set to right (R). At this setting the left L ignition coil was grounded rendering it inoperative.
o The engine died when the ignition switch was set to L. At this setting the R coil was grounded rendering it inoperative.
o On observing this result each of the A&Ps concluded (independently) that the problem must be the L coil, even though it was new and tested good when the resistance levels of the coil’s primary and secondary windings were measured.
Another possibility is that the ignition switch or the wiring from the switch to the coil is faulty. So, I did the following.
• Disconnected the P leads that run from the ignition switch to the ignition coils. By doing so, I eliminated the possibility that the switch was grounding either of the coils.
• This did not solve the problem.
I asked for help to solve the problem of the engine dying when the ignition switch is set to L.
Fortunately, the problem was solved as a result of a very useful recommendation of one of the members, Ralph Sanson. It resulted in the problem being solved. Please see below!
I would first ensure that left is actually left coil and right is right coil, this may not be the case. Possibly change the right coil and check.
I have done that. Did not solve the problem. Thanks!
Do you have an rpm drop when you go from both to R? You said it runs "fairly" smoothly on both, but "very" smoothly on R.
One thing I would check is the P leads that run from the ignition switch to the ignition coils. If the Left one was grounded by a crack or break in the insulation, you're only running on one coil (the Right one), and when you switch to Left, you intentionally ground the Right one, but wouldn't have any working because of the faulty "grounded" wire to the Left coil.
1. Did this just appear or has there been recent maintenance or a modification to the electrical system?
2. Can you sketch out and post up your ignition system diagram to include the switch and relays in the circuit?
Thanks! The problem cropped up about 5 months ago. It will take me some time to prepare the sketch.
Thanks! I will check out the leads.
check that the coil is not installed upside down
Many thanks Ralph. We have checked everything else multiple times with no positive outcome. Your recommendation is excellent. I will check the orientation of the coil when I can next go to the airport.
I switched the orientation of the left ignition coil so that the high tension lead pointed in the same direction as the flywheel and propeller. Then I started the engine and cycled the ignition switch through Both, Right, and Left. The engine ran at all of these settings.
Thank you Ralph for your excellent recommendation! I very much appreciate your help.
As soon as my A&P completes the condition inspection I hope to have the plane back in the air!
Congratulations, Gene. I always like to hear when a problem is solved.
I'm still learning and studying about my plane, and now, having followed your issue, when I go to the airport tomorrow, I'm going to take a close look at the coils. So far, I've only glanced at them, and never took a good look at them.
Thanks for your post Darrell. I'm very happy that the coil problem has been corrected.