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Old 03-03-2021, 02:28 PM
jnmeade jnmeade is online now
Join Date: Mar 2013
Location: Iowa
Posts: 181

Ah, so it is possible that when he says the engine starts he is only talking about on one CDI (EIM), not both initially.
My FD had old modules until recently. He could try starting it on the B module. If it works consistently, that simplifies trouble shooting. Or he could start on both and do a mag check to see which module is working.
The intermittent part is always a challenge.
The ice trick might work since the A module is on top (if they're stacked as on my two Rotax 912ULS).
When I had my ignition problem, I got help from Brett Lawton at Leading Edge Air Foils. He has a very systematic trouble shooting approach and is quite patient. Call Leading Edge and then dial extension 154.
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Old 03-03-2021, 03:30 PM
mbell mbell is offline
Join Date: Aug 2005
Posts: 141

It's hard to imagine that both modules are independently having the same problem, unless there is a common point. Any other thoughts? Mark[/quote]

If these are the old-style green-band modules, it's not uncommon that they would both have the same problem. It's a known weakness in the modules called a "cut-in" failure. They are supposed to cut-in at about 1,000 RPM, but instead they cut-in at about 2,000 RPM. So they run just fine if you can get the engine to start. The local (Northern California) Rotax guru says the capacitors get weak over time. The ice test will tell if this is an issue or not. Reviewing my notes from Rotax school, Lockwood says ice it for 20 minutes. In my case that worked every time, and the fix was a new module. Anyone interested in module repairs search the Rotax forum for the guy in Europe. Way cheaper, but not for me. I wanted new when it comes to ignition.
Mike Bell
RV4-->6-->6A, (built by Villanueva, Tolle, and Mosher)
AirCam finished and flying!
RV-14A under construction.
Cameron Park, CA (O61)
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Old 03-18-2021, 05:41 PM
n518jh n518jh is offline
Join Date: Jan 2015
Location: Sun City West, AZ
Posts: 46

Thanks for the various pieces of advice. BUT!!!
I installed a new ignition module from Leading Edge Air Foils. no joy!
That brings me to almost $2,000 out of pocket to find and fix my starting problem.
What I need is someone with diagnostic tools that can trace the 'juice' from the flywheel on through all the wires to the Spark Plugs. Does anyone know of such a person/tool set??? Does anyone want to buy a great RV12 with just a tiny problem??
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Old 03-18-2021, 06:07 PM
h&jeuropa h&jeuropa is offline
Join Date: Jun 2008
Location: Kalamazoo, MI
Posts: 290

Have you checked with Roger Lee in Tucson? He is a very experienced Rotax service person and frequent contributor to Rotax Owners website.

Jim Butcher
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Old 03-18-2021, 08:50 PM
n518jh n518jh is offline
Join Date: Jan 2015
Location: Sun City West, AZ
Posts: 46

Roger Lee has done some Rotax work for me, but when I called on this, he suggested he wasn't expert on the ignition circuits. I've taken the class he offers, about 2 years ago, but we didn't get into the details of how to trace for a bad circuit connection. Thanks for the suggestion. Mark
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Old 03-18-2021, 09:36 PM
jnmeade jnmeade is online now
Join Date: Mar 2013
Location: Iowa
Posts: 181

One new ignition module or two?
Does it continue to sometime start- and when it does it works properly on both sets of plugs - and sometimes not start, as before?

What Brett had me do initially was to take an old set of spark plugs and safety wire them to ground and plug the leads into them. Of course the engine can not start. Turn the starter over and verify there is spark on all plugs. Helps to have a dark hangar. I'm assuming if your problem is the same as the OP, either they will all fire or none will fire. But if only half fire, you can isolate it to one of the two ignition systems.

Make sure all the connectors are completely connected. The molex connectors should produce an audible click when seated.
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Old 03-18-2021, 11:10 PM
RFSchaller RFSchaller is offline
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 3,026

Have you ever tried an O-scope to look at the trigger coil pulses? Long shot, but it would be interesting to compare A and B trigger coil output.
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Old 04-05-2021, 09:15 PM
olegusan olegusan is offline
Join Date: Aug 2014
Location: Melbourne, Australia
Posts: 34

Had a similar problem with the engine not starting and not producing the spark at all on either of two ignition systems.

It turned out the the ignition unit grounding ring connector that is attached to the right intake manifold has become heavily oxidised.

Cleaning the ring connector and the place where it contacts the manifold fixed the problem nicely

See the image attached

.... or the link to the image
RV12 # 877
Melbourne, Australia
My DIY Avionics:
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Old 04-06-2021, 09:20 AM
Richard RG Richard RG is offline
Join Date: Jan 2021
Location: British Columbia, Canada
Posts: 21

Though I know close to zero about the 100 hp Rotax engine, did learn a little about it when I very nearly purchased a very nice Europa mono wheel with the Rotax up front. The deal breaker for me was when the engine initially wouldn't start, then when it eventually did start, ran very rough.
Upon removing the cowl noted the owner had tie wraps securing the automotive type spark plug leads to the lower spark plugs.
It turned out that the spark plug leads require a 'pull test' of some sort and could be a potential source of ignition problems on this engine, in part because it is a push on connection, rather than the old fashioned bolted up tight connection of the old fashioned airplane engines.
If I was dealing with ignition problems with this engine, would start with plugs (check resistance and condition) then check or replace spark plug leads, check coils and finally work your way back to the very expensive ignition modules.
If the ignition modules have failed, there is a supplier of overhauled modules in Sweden that sells for considerably less than buying from a Rotax dealer.
I fly behind an old fashioned Lycoming and must say I do like the old fashioned spark plug lead connections much better than those on the Rotax. Cheers
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Old 04-06-2021, 09:51 AM
Join Date: Nov 2007
Location: Jesup, Iowa
Posts: 1,673
Default More suggestions - -

The flywheel 'trigger' leads that come to the bottom of the ign modules are basically the same ( connectors ). The ign boxes are the same. If you carefully mark which is which to start with, you can disconnect, and switch to other component connectors to find out which circuit is the problem. Example - switch A circuit trigger feed to B ign box. Try to start on that system. If no ign, then switch to opposite ign box, and test again. Not giving total details, but you should get the idea. The connectors are the same. You can switch the components around to determine which item is the problem. Mark down what you did if this is confusing to you. Mark A and B circuits to start with so you can go back to original setup when you are done testing. Not sure I saw if you had green or yellow stripe ign boxes to start with ? ? ? ?
John Bender
Flying RV-12 - Serial #120036
Paid in May ( 5-2020 )
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