Ignition System Troubleshooting - 912UL

I had a similar, no spark, problem after an engine removal and reinstall. I chased that that no spark, no start problem for weeks. It turned out to be two pins in the ignition connectors had gotten swapped during the engine reinstallation. I swapped them back and everything worked fine. 

Solution found. Thank you for the suggestions, which eventually led to discover my error. Please see the attached photo.

Hope this explanation might help someone else.

My original System was configured with a 4-place plug and when I did the upgrade, I upgraded to a 6-place plug along with a complete new set of male and female connectors.

I ordered the new plugs from Leading Edge and either selected the wrong female ends or was sent the wrong ones in error.

Look closely at these connectors and you’ll discover a slight variation in the latching design, and size. The wrong ones fit quite nicely, but don’t latch.

I used the female connector on the right, but a combination of size and inconsistent latch design caused the male connector to displace the female connectors, rather than mate with them.

The result was that the new trigger coil leads and the ignition leads did not mate. The soft start feature powered the CDI’s, but no trigger signal was present and thus no ignition.

Your use of language is truly entertaining;

"...a combination of size and inconsistent latch design caused the male connector to displace the female connectors, rather than mate with them."

It's a good thing that biological entities are considerably more accommodating? 

I'm still unable to get the engine started, but I did get a couple of detonations while cranking. One kicked the prop backwards and a subsequent attempt was a backfire accompanied by smoke out the exhaust. I'm pretty sure I have swapped something - most likely the trigger coil leads. This is puzzling, because I traced the old trigger coil leads to each pin in the 4/6 pin connector and duplicated the positions (the new trigger coils did not arrive as a complete harness with pre-installed plugs).

While digging into the HMM, I see the following schematic on 74-00-00 page 6. Can I get a confirmation that this drawing is wrong? The arrow shows a counter clockwise rotation. 

This seems so straightforward - two trigger coil channels (A&B), connected to two CDI's (A&B), and four coils which fire two sets of spark plugs (top & bottom). 

Trigger coil A1/2 serves the top spark plug of cylinder 1 and 2.

Trigger coil A3/4 serves the bottom spark plug of cylinder 3 and 4.

Trigger coil B1/2 serves the bottom spark plug of cylinder 1 and 2.

Trigger coil B3/4 serves the top spark plug of cylinder 3 and 4.

I have ignition, fuel, and compression - it has to be an ignition timing issue. The engine ran fine (once original difficult starting issue was resolved).

What am I missing?

Hi David,

I talked about the ignition with ROTAX for general understanding for a few days and i writed it down in my homepage hkk-edv.de. Maybe my basic informations can help: Trust the picture and the rev direction, next you cannot see at the picture the diffenent levels of coil and cams, This means that cam and coil which are on the same level (displaced in depth) interact. Next see also 74-20-00. Its also important that sparks are generate not only for the power stroke, in the same time you get a spark at the exaust stroke. So if you had a mistake in harness/connectors you can get sparks on several times, sometimes a spark is on time at one cylinder at a power stroke - this can confuse. You canged the connectors. are you sure that no mix-up ocours? Use a simple labeling on every cabel/wire. I think its possible by this to find the mistake. Good luck. 

Edit: Your first picture is great - I used it on my site, if you don't allow it I'll delete it immediately.