Ignition Module Mounting Issue

[AaronWhitaker]

I had a really close call yesterday. I had checked out the plane, done the run up, and everything was good. I lined up, took off, and the engine started missing and eventually quit. Fortunately, I was taking off from a long runway and still had plenty left.

After I got back down and got the cowl off, I found the problem right away. One of the steel straps that the ignition module mounts to had broken. It just so happened that this particular strap was also the strap the grounding wires were attached to. The wires were attached at the top where the strap attaches to the rubber vibration mount. When the strap broke, it came free of the engine and lost ground and the engine died.

This was one of those, "Why didn't I think of that?" moments. The mechanic at the FBO suggested I attach a ground wire and bypass the strap and connect directly to the engine block. That way if the strap breaks, the engine won't kill.

This wasn't the first time the strap had broken. For whatever reason, we didn't lose ground the first time. The second time it did. I talked to John McBean at the flyin last fall about it and he said that he hadn't heard about that happening although the FBO mechanic said that is the most common problem he has seen on the 912.

Anyway, this time I was very lucky. I am glad it didn't happen up in the mountains. Has anyone seen this problem before? If not, maybe take a look at your ignition module installation.

[DesertFox4]

Good job flying the airplane Aaron. Glad you had runway left. Thanks for the valuable info.

I've had a double ground on my model 4's ignition since birth, just in case. I moved my ignition modules back to the firewall part of the motor mount to isolate them from the constant engine vibrations.

[catz631]

Aaron,
You are a lucky guy indeed ! Thanks for posting this. The modules on my engine also broke a strap and I mfg a new one. Found it during the annual. My grounds are fastened at the engine block with a long cap screw. Now I see why.
I think Steve has the best idea using the firewall. It would require some mods to do it though.
Dick

[AaronWhitaker]

How would you move the ignition module? It would require longer plug wires but the wires look like they are potted permanently into the ignition module. Just from a quick look it doesn't appear than you can swap out the plug wires. Would I have to buy a whole new set up with longer wires?

-Aaron

[catz631]

Yeah, how did you do it Steve. Show us a picture !
Dick

[SkySteve]

Aaron,
They unscrew. Just turn them counter clockwise.

[DesertFox4]

Guys , take note that mine is a model 4 so differences in the mounts may be a factor in weather your ignition module pack may be relocated to the rear portion of the motor mount without buying longer spark plug wires. Not sure about newer models. I did this on my model 3 also.

Here is a link to Dan's build site for one way to do this. He just did it on his model 4 with a 912S. I don't have a current photo here at the house and will be a few days before I get out to my hangar.

Scroll down just a little and click on his May 29-31 post and you will see some brackets made to hold the ignition pack. He used the rubber mount that comes on the Rotax to fasten the rear of the pack to the welded in "web" reinforcement just forward of the oil tank.

http://www.azshowersolutions.com/Build1.html

[DanB]

I ran across these pics yesterday and thought they would also help w/ this thread. This shows Steve's coils and the bracket he made to cradel them. The wide piece of aluminum wraps under the coils and comes up the other side. There is then a bolt that goes through the front bolt hole and spans both sides of that cradel. Very stable. SteveIgn2.jpg
SteveIgn1.jpg

[kmach]

I am also interested in seeing a picture of the ignition mount mod, do you require special spark plug wires ? I know that they would need to be longer. a picture is worth a thousand words! Kevin

[kmach]

I am also interested in seeing a picture of the ignition mount mod, do you require special spark plug wires ? I know that they would need to be longer. a picture is worth a thousand words! Kevin

Please excuse my post , I didn't hit the more replies below option. The pictures show it well, it looks like a real good idea . Kevin