Starting 912s

[Boet]

No, but my own experience.

[Morph]

Well I had an interesting one on Saturday.

EPH gave the same frikken symptoms of cranking away but not starting. So back to stripping off the cowling and the bootcowl, to get to the battery. Under advise from my mate Ranger I beefed up the earthing wires to the motor. This time she cranked a lot faster but still no firing. Then Ranger and Mark (a Morning Star mate) checked whether I was getting fuel through, which was fine. Mark removed one of the plugs and found that there was no spark during cranking. Ranger then asked me to crank and touched the ignition boxes and she instantly fired. . I quickly killed the motor and we checked the wiring on both units, making sure all the plugs were secure. Another crank and no spark. Obviously it had to be something common to both boxes.

This time Ranger wriggled the ignition boxes and she started again. On closer inspection we found that the boxes are isolated from the engine by rubber mounts and rely on an earth to one of the brackets. The nut holding this bracket was loose After tightening this the engine fired instantly. After a test flight I proceeded to prostitute myself for free by taking everybody who was available for a flip. Weather was awesome, silky smooth and in no time (2 hours actually ) I had burned the 25 liters.

hmmmmm, now what is the weather looking like this week.

Thanks for the help guys, some things you simply cannot do on your own

[Trikenut]

So instead of uh,uh,uh,uh,uh,uh,uh,uh,uh,uh,uh rattle, rattle, vroom! Its was uh vroom!!!
Nice work guys!

[Massimo]

And 99.999% of the time its a simple stupid thing like that or like my flat battery. And we often jump in and look for all sorts of complicated stuff.

[Oupa-G]

Morph the problem is only one earth that then becomes a single point of failure each ignition unit should have it's own earth. In the Bosvark we concentrate on the avoidance of single points of failure. Just a little snippet. Will see you at the meeting on Wednesday.

Cheers Oupa-G

[Stephan van Tonder]

Eish that is just plain scary.

[Morph]

Morph the problem is only one earth that then becomes a single point of failure each ignition unit should have it's own earth. In the Bosvark we concentrate on the avoidance of single points of failure. Just a little snippet. Will see you at the meeting on Wednesday.

Cheers Oupa-G

Good point Oupa G. I will give them individual earths

[Mogas]

Glad you guys found the snag and thanks for posting the solution.

[Morph]

Look at this exploded view of the ignition system taken out of the manual. Here you can see a single earth connection to both ignition systems as well. Based on my experience I would recommend this be changed.

I had a look at a 914 yesterday and it uses two different grounding points on the manifold. I only have one.

[Boet]

Thanks for sharing this learning experience with us. I have 2 x 912 engines standing here, and yes, same prop. This will be changed. another day, another valuable lesson learned. Sorry I can`t make tonite`s meeting. Enjoy the company!!

[Cali]

Man isn't it great when a HUGE problem that has you pulling your hear out, is solved with no or little cost and a lot of experience gained.
Have fun flying boys.

[Morph]

On another thread discussing high EGT's on the 912 it was found that one of the earth wires had come loose, resulting in one ignition system not working. This caused the high EGT condition.

[Splinter]

On another thread discussing high EGT's on the 912 it was found that one of the earth wires had come loose, resulting in one ignition system not working. This caused the high EGT condition.

Thanks Morph that is correct! We found the same problem on the topic "912UL EGT`s Running HOT". Please read the topic and keep the symptoms and possible solutions in mind.

RED

[Massimo]

Damn 2 earths, that makes alot of sense. Thanks guys.