Rotax 912 "Mag" problems (older style ignition)

[@kimprout1961]

Thank you Jim for posting this video…I think I owe you a nice lunch! I was doing my usual run-up when all of a sudden the (L on switch) A module completely cut out then was ok a few switch turns later then cut out again. I did indeed find the break in the wire as you described and that saved me a ton of time tracing all the circuitry or assuming a bad module. I did check the ignition switch first but it checked out solidly. Thanks again for taking the time to post this video. 👍😁

[@LightAndSportyGuy]

Glad it was helpful! Also check the ground wires where the wires connect to the engine.

[@leehewitt9559]

Interesting and helpful video. Probably vibration over the years that’s caused the wire to break inside the insulation.

[@srnunan4783]

I’ve also had broken wires on the ignition modules etc but I’ve also had to replace two trigger coils at different times due to the old ones going open circuit, it may be that the broken wires caused the coils to fail.

[@madmarkstoys]

had the same problem always had a rough running 912 at idle I had a fractured wire right at the CDI box lucky I had enough wire left coming out of the CD box to solder and Shrink tape and isolate the wires from vibration I sync my carbs with the broken wire so make sure you resync your carbs after you fix a fractured wire

[@buburuzu77]

Thank you for sharing !! I will check my wires first !!

[@michaelvadney5803]

Hello Jim. I have a 912 ULS, a 2008 model year, that has a bad "mag" check. On one switch the engine's drop in rpms is only like 100rpm, but on the other switch its some where between 750 to 1000 rpm! I have been debugging this problem for 2-3 weeks now with no real progress. I even purchased and installed a new pickup set with harness. I have the newer, 6-pin version of ignition too. Here is what I tried: 1. Swapped the 6-pin plugs where they connect to the two ignitor/cdi boxes. The problems stayed on the same mag switch. 2. Next I swapped the two red magneto supply lines to the 6-pin plugs. Again, stayed on the same switch. 3. Replaced the pickup coil set. Yep, exact same problem and on the same switch remains. 4. I ran the two mag, ground wires directly to ground one at a time to see if it was some how the mag switches, but the same problem remains. My rationale is that if swapping the 6-pin plugs did nothing then it cannot be from the 6-pin connector all the way down to the sparkplugs. Otherwise the problem would have jumped to the other switch. The same idea for the two red stator supply wires to the 6-pin plugs too. I am at a loss of what to try next. Any guesses? Thanks!

[@LightAndSportyGuy]

Have you switched all the plugs between top and bottom? Seems like that's about all that is left...

[@michaelvadney5803]

Top and bottom plugs? I first swapped the 6 pin plugs between the stator, mag switch, and pickup coils where they connect to the A and B boxes yes

[@LightAndSportyGuy]

@@michaelvadney5803 Sorry, I wasn't clear. Have you taken the top spark plugs out and put them in the bottom holes - and bottom spark plugs in the top? Check to see if the problem follows the spark plugs.

[@madmarkstoys]

did you ever figure out your problem

[@michaelvadney5803]

Yes I did actually. It turned out that I did not need to replace the pickup coils assembly at all. When I purchased the engine used the A&P for some unknown reason unbolted the pickups at some point when he swapped in a new engine. When he reassembled the pickups on the engine block he omitted the standoff collar on one of the two pickups. So basically both pickups were using the same timing tabs. This also caused a high EGT issue on climb out. Good power, but it built too much heat. No clue why he happened to do that. If he didn't than I would have saved $1000 ducks and had a happier summer.

[@Kolbra2004]

If I ever have ignition problems, it's good to know. Thank you ...

[@LightAndSportyGuy]

Thank you for the comment.

[@portnuefflyer]

So, does the plane's battery, with it's amp hour capacity, not provide enough power to run the engine, at least for a little while? To put it another way, does a shorting wire in the stator assembly IMMEDIATELY make itself known? Is the CDI power, instant by instant, coming from the stator coil, OR, is it coming from the battery?

[@LightAndSportyGuy]

The battery is not connected to the ignition. All the power for the CDI comes from the coils under the flywheel.

[@portnuefflyer]

@@LightAndSportyGuy Ahh, I had it wrong! So yes any misfiring connections will make themselves known as they happen/when they happen, thanks.

[@LightAndSportyGuy]

@@portnuefflyer I should be clear, I am addressing the carbureted 912/914 ignition. I think the fuel injection / EMS systems may connect to the battery as an extra power source.

[@LeonardLayne]

Thank you. Great info👌

[@darrylwbraun]

Ok... I don't know if this is my problem but I'm sure glad I found this video. I have the same problem but it's not one mag over the other, it's both. I was leaning toward the Rotec TBI I've been trying to get running but maybe this is the problem. I did find a charging wire with bad insulation, that I fixed, but maybe it's broken somewhere else too. Thanks, I've got some more work to do now

[@LightAndSportyGuy]

Check the ground wires as well. The service manuals give the expected resistance readings for the coils in the ignition system.

[@darrylwbraun]

@@LightAndSportyGuy I have the heavy maintenance manual and it doesn't match my wiring. The colors are all wrong and I don't really know which pins to check across. I did clean all the ground wires and had a realization yesterday. The engine was still running very rough, till I pulled the mixture about 3/4 out. And, closer to idle I have to pull it all the way out. My problem seems to be a massively rich mixture, like running on full choke. This Rotec TBI, specifically the fuel regulator, is just not working right. I'm now rebuilding my carbs just for comparison. If it runs, I'll dump the TBI. If I can get the TBI working I'll see the carbs.

[@spurgear4]

Same issue with coil ground wires.

[@LightAndSportyGuy]

Thank you for that.

[@acensor]

We have the exact same symptoms on our 20 year old 912. Only difference is our symptoms surface only when the engine has been running about 18 minutes (and we assume it's a matter of temperature under the cowl.) Jim... It sure would be helpful if you'd show a video or photo of exactly where the suspect (internally broken) leads are. And how you fixed. Would you be willing to do that? Did you just splice on a good end?

[@LightAndSportyGuy]

2:01 The area circled in yellow is where the red wires plug in near the ignition coils on top of the engine - easy to get to. Wires were broken right where they go into the crimp and right where they come out of the shielded harness. Later I found a broken wire where there is a cluster of ground wires bolted to the right hand intake manifold just forward of the ignition module. I slit the shielding back a bit, spliced in some new wire with new ends and used heat shrink to hold the shielding back in place and protect the splices. Rotax recommends replacing the whole harness/ coil assembly. kzbin.info/www/bejne/hIrSaIujpKholbM the broken red wires are right under my left thumb in this video. Sorry I didn't include a picture of where the break was.

[@acensor]

@@LightAndSportyGuy Thanks much for your reply! Hey... I hope your video isn't implying I have to remove the engine and/or the cover of the flywheel to reach and check those wires or replace the harness?

[@LightAndSportyGuy]

@@acensor Checking the wires with a meter can be done at the connectors which are close to the ignition module - easy to get to. That is also where it appears to me they are most likely to fail - things are pretty well supported at the coil end. I didn't even need to use a meter - just a gentle pull on the wire showed that the insulation was stretching because the wires inside were broken. If you decide to replace the harness and coils (all one unit), you need to get access to around the outside of the flywheel - you may or may not have room to get in there with the engine in place.

[@eclipso104]

Did you ever fix your issue? Mine seems to do the same as yours sounds. It gets up to temp around 190 to 200f and then starts miss firing on one ignition system.

[@bennietipton2820]

Good information

[@LightAndSportyGuy]

Thank you for the comment.

[@jurisbruzuks4288]

To the attention of Rotax aircraft engine users! This engine worked for 210 hours and fell apart during the flight in the air. The reason was oil starvation of one crankshaft journal. A preliminary inspection showed that the problem was from the very beginning and the connecting rod at least received lubrication from the crankcase. But it wasn't enough and the connecting rod with the bushing, having received a large gap, collapsed. From beginning of operation with a warm engine, when the speed was reduced to a minimum, the temperature and oil pressure began to rise. By adding speed, everything returned to normal. The company ROTAX does not recognize their marriages!