80 HP 912UL will not start

by David Wallis in 912 / 914 Technical Questions 10 years ago

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Re: 80 HP 912UL will not start

by William Campbell » 10 years ago

William Campbell

15 25 43

With all this being said my sources say how can both modules be bad? When heating the top module with little or no heat going to the bottom one why does it run ok once it starts and I flip each mag to see if one ignition is inoperative and they both check ok. This engine did set in a cold damp hanger before I bought it so maybe the elements got to them. I, like you are going to change both of them out. I would think the ones on my engine now have dried out since the engine has been been run on some 100F days for hours on end and we do not have any humidity here in Fresno, Ca during the summer.

As an aside, awhile back some suggested I put some Ice on the top module and the engine did start as well. That only worked one or two times and I could not buy into it as the temporary fix to the module. Again how can they both be bad unless the bottom one does not start working until the engine has started and RPM's permit a higher voltage to be generated by the flywheel and coil on the back of the engine. Just a thought.

Again thanks for sharing your experiences with me. I will let you know how this all shakes out in the end. Have you looked at the Bullyhawk soft starts at www,bullyhawk.com?

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Re: 80 HP 912UL will not start

by Roger Lee » 10 years ago

Roger Lee

125 5.12k 4.53k

I have seen both modules fail several times. I wouldn't nickle and dime purchasing modules. Just get them and go fly or you will be beating you head against the wall and be down for a long time. You don't know what caused the modules to go bad and may have affected both (i.e. heat). One may have been bad until the second failed. Don't buy and install one new style soft start module and use it with one that isn't a soft start.

Just for an FYI;
Just had a mechanic friend in New Mexico with two engines with bad modules.t. Pulled a used set off an engine that had a bad lifter that had sat for 6 months. Another set of bad modules. Bought a set to put on and issues solved.

I hate to say it like this, but sometimes it's easier to just suck it up and get back in the air. Things happen and until forums became really popular you never knew what was going on in another state much less the world with everyone's planes. Now the world is smaller with instant communications and forums like this so now you hear about everything. Some times it may sound like a lot of issues, but with the shear volume out there and the poor maint. on some enginse you can and will hear of issues far more than you would have 15-20 years ago.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

Thank you said by: William Campbell

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Re: 80 HP 912UL will not start

by David Wallis » 10 years ago

David Wallis

2 13 0

Again, I can not take credit for discovering this problem and temporary solution. I googled it. I am not a engine mechanic or electronics tech. I do have a mechanical background though.

That said, what I have learned elsewhere is that the lower module goes bad and the engine will start on the upper one. Then when they run for a very short time the lower will come back to life. When you get the engine up to operating temperature the mag check is good. I have no clue why that occurs. The Electronics inside the module might have come from a new production run or different supplier.

I fly a ELSA Weight Shift Trike and the modules have lots of cooling air compared to a engine buried inside a hot airplane cowling. But they failed anyway so I can't blame heat so much. I usually try to cool down my engine a bit before I shut it off.

I started my engine yesterday without the hot air and it ran just fine. Shortly thereafter I did a low rpm mag check and both mags were firing. I have absolutely no doubt if I let the engine set for a week or two it will not start. If you run the engine every few days it will stay good until they ultimately both completely fail.

I have no idea what the warranty is, but 7 years would be a stretch. Nothing's forever. And I suppose the current half off price is nice to get although they should have lasted much longer, in my opinion.

Thank you said by: William Campbell

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Re: 80 HP 912UL will not start

by itemprop='name' » 10 years ago

0 0 0

Hi dave

One of my pet hates is those modules , in Australia there has been a lot people had failures with those modules . They seem to have a few failure types the hard starting i(weak spark ) we have found mostly due to caps in inside loosing there ability to hold a charge. But normally once the engine is up to speed there don,t show to be a problem but you have to throw the $800 unit any way for a one dollar item . A few units have gone dead totally throw a chip failure again a $3 item, there is a few guys over here which used to design circuit boards for a living have pulled them apart .They have worked out the circuits a have found a few design faults and to be honest the rotax modules are not the best put together rough in side and they have things like heat sinks that go to no wear just to the middle if the epoxy block so don't transfer heat. It's around about a 30 dollar main module board inside one of the guys here prices board design for a job and has costed it out . I,m not sure how rotax can make a aircraft motor with out any aircraft grade wire in there motors . So you where lucky to get the time you did out of them . Heat and cranking motor with out all pugs grounded are the to main causes to module problems we have found . Both causes could be easy designed around but hey 800 dollars each is good money to keep making them not last . For about a 40 dollar item .

Good luck.

Dan

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Re: 80 HP 912UL will not start

by paul harrington » 10 years ago

paul harrington

3 9 0

It is strange that you all are having problems with the modules. It seems that many parts were subcontracted out at some time in the early 2000's and a hell of a lot of problems have occurred. My 912s (certified) was produced in 1996 and the modules have never given a seconds problem. I see most AD's on the engine concern parts produced after 2000. Now, because my engine is over 12 years old I can only fly 'On Condition'. The engine has only accumulated 780 hrs and apart from a preventative cylinder head overhaul and a carby rebuild, has run well since new. It has also had very few AD's that required attention. Rotax must hate me, they haven't been able to screw much money out of this model and local farmers here are running Rotaxs' of this age to well over 4000 hrs. You'd think that some of the later models were built in China.

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80 HP 912UL will not start

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