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Rotax 912 Ignition Problems.


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Time to start a new thread on this one.

 

Rotax 912S won't start. .No spark at all. A real mystery for two independent systems.....

 

I realize that it can be difficult to see a spark on some engines, but a couple of very experienced mechanics peering carefully inside a darkened hangar, looking for a spark across the plug gap. Also know that the other HT lead from each coil must be connected at the same time.

 

The mystery: It would seem strange that both sides of that ignition system could fail at the same time.

 

The clues: But thinking about it, they probably didn't fail at the same time. I had a Soft Start Module on the one side, so used to start with only that side switched on. A couple of months ago noted that it sometimes wouldn't start on that side alone, but fired instantly when switching on the other side. Thought it might be the effect of the SSM so disconnected it. Didn't really need the SSM any more, because I'd since installed an Odyssey battery right behind the firewall, with heavy leads direct to the starter motor, so the cranking speed was so fast that it overcame any tendency to kick-back. (I've been joking that it's just about fast enough to fly on the battery alone....) But those mis-starts might have indicated that the ignition system on that side was losing it's ability to generate a spark, even at that cranking speed. I've always done mag checks at 3000 rpm, so nothing showed up then. Without the SSM I was once again starting with both switches on, which would cover up the weak side, until the second side also started to lose it's effectiveness. And it was gradual, there's been several times in the last weeks that it was difficult to start, but finally did and then ran well with good mag checks at 3000, so the problem was blamed on flooding.... I now realize that a good procedure would be to occasionally start on one side at a time to test each side for such a starting failure.....

 

Disconnected and tested kill switch wires.

 

Resistance measurements of coils, pickups and charging coils, as per Heavy Maintenance Manual, are all correct.

 

Pickup gaps checked correct.

 

Ignition modules checked OK by B Flood.

 

Next will check the wiring inside the shielding between the stator and the modules... Have since heard of another intermitent fault that involved damaged wires in there.... It's just such a hassle to tear it all apart....

 

Only component common to both sides is the flywheel/stator.

 

Recently had a similiar problem on an 80hp on a Pegasus trike. Unfortunatly it did turn out to be dead stator for some reason. Wal called it a 'lazy' stator. It was so lazy it was dead !!. Also found one ign pickup completely dead. A lot of people will suspect the IGN moduals/boxes, but I haven't had too much drama with them over the years. Good luck.............................................. ...............................Maj..

 

Maj - That sounds very much like it fits the clues. How do you test that without replacing it???

 

JG

 

 

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f you remove the flywheel and stator, you may find the cables in similar condition underneath  to what you found further up. If you pick away the potting where the cables terminate at the stator

Dan To help you with this I went to the hangar this morning and I did some measurements on my test rig for the voltages coming from the CDI coils in the stator. The measurements are engine RPM th

This is the sort of damage I found after stripping back the conduit which had no visible damage. Very similar symptoms....Working just fine the wouldn't start one day. No spark. Changed modules..

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Guest Maj Millard

JG, Just a matter of running out of everything else really, so that it is the only thing left. The operation of the rotor/stator relys on good ol magnetism. There's only one thing that will upset magnatism and that's high heat. Two things can ruin the IGN moduals. Hooking up you battery incorrectly (even for a second) or turning over the engine with the plug leads off, and with the switches ON or disconnected. The boxes produce a lot of jolts, and if it can't dissapate by grounding out through the plugs, it goes back into the boxes and zapps them.

 

Don't like Oddessy batterys myself, there way too expensive and no better than a good lead-acid. I am starting to see just as many dead ones around the hamgars, now as other types. I have always run Yuasa and generally get a good four years out of them. The charging set up on Oddessys is strange and Rotax charging coils/regulators may not want to talk to Oddessys for charging purposes. Could be my imagination, but I seem to see a few IGN problems lately with people using Oddessys. Just my thoughts............................................Maj..024_cool.gif.7a88a3168ebd868f5549631161e2b369.gif

 

 

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I'm no genius on Rotax, but my first thought was that if both modules had failed to spark, then it had to be something common to both. The likelyhood of both failing at the same time is too remote to consider.

 

Therefore the first place I would check is the grounding cct to the kill switch/s. But on further reading you seem to have covered that. I would even have checked the switch/s themselves. If they have mechanically failed internally they may ground out. And may do it intermittently as well.

 

That was my thoughts. Not very technical, but then these problems are sometimes really simple.

 

The next place I would check was the charging coils, but you seem to be doing that now. It would now be up to the people that really understand these things.

 

Probably not very helpful, but there you go.

 

Best of luck with it. Will be good to read about the outcome.

 

Ding.

 

 

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A few more straws to grab at

 

Some Ads, sounds like grounding.

 

To increase the TBo Hours on some engines says something about replacing the stator etc >> ie known problems

 

Civil Aviation Safety Authority - Piston engines

 

otax Piston Engines

 

AD/ROTAX/2 Ignition Electronic Module 3/95 TX

 

Applicability: All 912 A series engines with serial numbers 4,076.062 to 4,076.220 inclusive.

 

Requirement: Inspect, and if necessary, repair the grounding cable assembly on electronics module

 

Part Number 965 356, in accordance with Bombardier Rotax Mandatory Technical

 

Bulletin 912-06 dated 21 November 1994.

 

Note: Austro Control (Austria) AD 80 dated 28 November 1994 refers.

 

Compliance: 1. Prior to further flight after 12 January 1995, but no later than 31 January 1995.

 

2. Prior to installation of an electronic module on an engine.

 

Background: Bombardier Rotax have reported that production machinery problems have resulted in

 

the electronics module grounding cable lug being incorrectly fitted, this could result

 

in engine misfiring or stoppage. This Directive requires the cable lug to be inspected

 

for correct installation.

 

 

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I'd check the magnetism of the stator - flywheel. I've had one of them fail on a stationary motor once.

 

Just had another thought, have you checked the battery power? as in the starter motor current draw, sometimes the starter can pinch all the power from the coil, thus a weak or if any spark. The Rotax 503 does that sometimes, if the battery is a bit low, it won't start even though it's turning over quite fast. You just give the prop a flick or get some more power for the battery, and it will start - basically to spark!

 

Just a thought.

 

 

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The ongoing story.....

 

Sent the ignition modules to B Flood, checked OK on their test bench.

 

Got them back and installed one of them on another engine - NO SPARK there either......

 

I've now heard of another engine that had no spark on both sides, modules tested OK by B Flood, but engine still wouldn't start until modules were replaced by new ones.....

 

So I've just ordered a new module from a friend in USA who used to service Rotaxes and has it in surplus stock. ONLY A$850.........

 

 

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  • 2 weeks later...

Have you looked at...

 

I had an ignition problem on my 912 that had me puzzled for a while. The wires coming out of the alternator are covered with a fairly robust shield. This shield ends with a plastic cover that makes a neat but tight exit for the wires that power the ignition modules. Over time the wires had flexed at this point and broken the copper wire inside the PVC cover. The break could not be seen from the outside, and when testing for continuity, the act of pressing the multimeter probes onto the ends of the wires re-made the circuit, so that I could not see the fault.

 

A neat trick for connecting onto a wire for testing without having to cut it, is to push a pin or a needle through the insulation to make contact with the copper wire on the inside. I used this technique to test the wires right where they came out of the alternator, and this confirmed that that the wires inside the alternator were not the problem - a big relief, I can tell you!

 

Remember, the power to the ignition modules comes directly from the ignition winding on the alternator, and has nothing to do with the battery or rectifier. The on/off switch connects in here as well, and if this faulty, it could be the problem too.

 

Jack. :):)

 

 

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Good point, I've now heard of another that had a similar problem in the wiring in that shield.

 

But now that I've tried one of the suspect modules on another aircraft and find no spark there as well, I think it's pretty much focused on the module itself now. Just waiting for a new replacement to arrive.

 

JG

 

 

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Yesterday received a new module.

 

Installed on 'A' side.

 

Saw no spark at first while cranking......

 

Then more cranking and a good strong spark, but also now a spark on the B side with the original module which didn't spark before....

 

Engine now started immediately on A alone, or B alone, and mag checks good at all revs from 1400 to 3000rpm.

 

Replaced the original module on A side to check it again. Wouldn't start.

 

Started on B side, and wouldn't run on A side at less than 2500rpm, mag checks good above that speed.

 

After about one minute of running, 'A' side decided to run well right down to 1400rpm...

 

Now starting easily on A side old module alone....

 

These clues don't help narrow the mystery, but make it even more confusing.....

 

???????????????? Puzzling......

 

Going out to the airfield soon to see what surprises today will bring....

 

JG

 

 

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Guest Escadrille

Hey JG,

 

Heres hoping that ole Rotax keeps running when you need it most!

 

I know how it really gets you attention when they don't!!

 

Good luck and Best wishes...

 

Hope to catch you in a little while with reports on the VGs I installed on the Jabiru,

 

Andy

 

 

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JG3,

 

Matei would be checking wiring real closely, not saying you havent already, but that just doesnt add up, after getting it warm the old module now works, usually electrical parts work the other way good cold, bad, warm or hot. I feel your frustration thou :)

 

 

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This morning it wouldn't start on the old A module, but did start on the old B.

 

Once running it wouldn't run on the A side at lower revs again, but after less than minute of running then it would run on A right down to idle, and restart again only on A..... Not running near long enough for temperature of the module to change....

 

Thinking now that the significant clue to follow may be that the new module didn't show a spark at first cranking, so maybe it's not this old module that keeps changing it's mind, but something in the wiring after all. Maybe the running engine makes a contact re-establish...

 

But that doesn't really explain why it would run above 2500pm but not below, and then a few moments later run fine right down to idle.....

 

Probably two intermittent problems happening, independent of each other, which makes logic really confusing....

 

Sure wish I could find something broken and just replace it....

 

JG

 

 

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Is there an excessive RPM drop when testing

 

ignition systems independently?

 

YES

 

Ä

 

1. Check carburetors first. Activate choke. If there is a change, sus-

 

pect the carburetors.

 

2. Clean grounding terminals

 

3. Check pick-up coil gaps

 

4. Swap the position of the red charging coil wires to the electronic

 

modules. If the problem remains on the same mag, the charging

 

system is OK. If it shifts, the stator coil, its wiring or its grounding

 

are faulty.

 

5. Swap positions of the pick-up coil connectors. If the problem shifts

 

there is a faulty pick-up.

 

6. Install new spark plugs, inspect spark plug caps and measure their

 

resistance and the secondary coil’s resistance.

 

7. Swap ignition module A with module B, measure their primary coil

 

resistance (on new style modules the ground goes through the

 

connector). If the problem moves, there is a faulty ignition module.

 

Ignition system

 

http://www.rotaxservice.com/documents/troubleshoot4ST.pdf

 

 

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With the new module on A side, it starts every time - so far.....

 

So I guess the old module is marginal and intermittent at low revs.

 

The old B module starts now, but didn't before, so maybe not quite as marginal, but needs to be replaced as well....

 

At least neither one ever even hesitated at flight revs.

 

Now the question - why???

 

I don't think it was ever cranked with leads off and nowhere for the spark to go, but maybe.... That's just the sort of thing that could do the damage....

 

Sure be good to get flying again!

 

JG

 

 

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>At least neither one ever even hesitated at flight revs<

 

Guess-to-mate

 

Have you tried electrical spray cleaner on the terminals, ? contamination, the connections could look clean but have a film over them nudge the spade connectors a little tighter.

 

Module a AND b have one connection in-common , so for that to be the case, Original A would have to short depriving B of power. Why would a short go away at rpm?

 

I vote for the cabling, How much is the stainless covered loom$

 

I believe before it was not covered, and was upgraded to improve reliability, may also force more stress where it is not covered

 

Lets hope you have solved it anyway

 

Good luck

 

Have you tried Matronics they have a rotax forum not sure how popular it is.

 

 

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That's some serious confusion alright JG! I can just imagine your frustration!!

 

I hope it works for you now.

 

Just for interest sake, a customer had an engine that would run for about 30min's and then stop, wait for about 15min and it'll start again, and away you go for another 30min!!

 

He couldn't figure it, thought it must have been some sort of practical joke! Anyway we found it to be his coil, when it got to a certain temp, it would cut off! Or coil clearance would close sufficiently to make it stop working. (wasn't an aircraft engine btw - Honda I think)

 

Electronics for ya!! (where is our diesels!)

 

 

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Guest Maj Millard

Hi John, It's sounding a bit like a coil problem to me also. Have you tried substituting them at all ..............................................................................................Maj..024_cool.gif.7a88a3168ebd868f5549631161e2b369.gif

 

 

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With the new module on A side, it starts every time - so far.....

 

 

 

So I guess the old module is marginal and intermittent at low revs.

 

 

 

The old B module starts now, but didn't before, so maybe not quite as marginal, but needs to be replaced as well....

 

 

 

At least neither one ever even hesitated at flight revs.

 

 

 

Now the question - why???

 

I don't think it was ever cranked with leads off and nowhere for the spark to go, but maybe.... That's just the sort of thing that could do the damage....

 

 

So it does appear to be the module after all.

 

Yesterday I was doing lots of flight testing of reflexed flaperon settings, so many shut-downs and start-ups. Always started on the one module, and never a miss....

 

I'm guessing now that at an oil and plug change I must have cranked the engine with one or more plug leads dangling. That can cause tremendously high voltage spikes that have nowhere to go, and surge back and damage the primary side of things. I know that we must always put a plug back in the connector and lay the base of the plug on the engine block so that the spark can go safely to earth. But there are 'seniors moments', always have been come to thing of it, never was all that smart........

 

JG

 

 

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Guest Maj Millard

Yes John, leaving the plug leads off and cranking will cause damage to the Ign moduals. It's a known no-no. If you have separate IGN switches you can crank with the switches off, but some have the IGN combined within the key switch, so then the plugs/leads have to be grounded as you say.I just did a quick trip down to the Hunter Valley from Townsville, and return, in the Lightwing, and I have to say the 912 ULS performed faultlessly all the way.....................................................................Maj...024_cool.gif.7a88a3168ebd868f5549631161e2b369.gif

 

 

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  • 2 months later...

G'day JG3 and other contributers:

 

I have read this thread with great interest. I have a vaguely similar problem with my Skyfox CA-22 912 UL in that, after a rest of 15 months, I cannot get the 912 started. After considerable messing about, problem seems to be that the spark from both IGN modules is very weak. This particular problem has plagued me for several years - very difficult starting that has got slowly worse with time. Today I turned the engine over with no compression in any cylinder, but each HT lead going to a properly connected plug externally and producing a very weak spark. All four HT coil secondary windings measure similarly on a DC meter- about 8 K ohms DC, as best I recall - could be more or less, but all about the same and no obvious leakage to ground on ohms X 1K. Not sure of the turning rpm, but more than sufficient from past experience - will measure it in a few days. I note the manual re the "Interference Suppression Box" containing the two IGN circuits says (Sect. 6.18.5 in my 1992 version) "Apply Lithium grease to all cable connections to prevent leakage currents". Like others, I have occasionally been guilty of turning the engine over without every spark plug properly connected. However, if this was the problem, I would expect to have a problem on Circuit A 1T and 2T (usually pull 1T or 2T plug to check spark), rather than the whole shooting match. Maybe excess leakage fits the bill better? Have other owners pulled the leads off and used a Lithium grease to inhibit leakage? What's the latest on your problems, JG3?

 

Also, I don't understand the "dead" or "lazy" stator description - a stator has the 10 coils mounted, but is not magnetized itself - is that not so, or do I have it wrong? I thought the magneto ring had the magnetized bits?

 

 

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This first link Failed Ignition Circuit on Rotax 912SP

 

BMAA Forum

 

http://contrails.free.fr/fichiers2/d03243.pdf

 

Bully Hawk Aero Performance, Rotax Performance and Upgrade Kits

 

The Soft Start Module (SSM) alters the timing on one ignition circuit. It has been found to be highly beneficial on 912ULS engines fitted with a slipper clutch.

 

The real cause of these problems is inadequate batteries and long starter cables resulting in slow cranking speeds. The Soft Start Module helps overcome the problems caused by these short falls.

 

 

 

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I finally replaced the A module with a new one. The old module on the A side would run once the engine was started on the B side, but wouldn't run below 2500rpm on just the old A module. Earlier on I couldn't get a starting spark on either the A or B module, but the B module now does start the engine. So I placed the Soft Start module on the B side, and always start on that side now in order to keep an eye on that module. I just did a 48hr cross-country trip with no problems. So the mystery is unresolved...... I sure checked thoroughly for bad earths and leakage, but couldn't find any problems.

 

I note that the standard modules supplied by Rotax now have a soft start feature built in.

 

JG

 

 

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Would be interesting to put module one back on and have jumper leads on see if the extra power can spin the motor fast which should produce more power for the ignition .

 

I also ran two Earth cables from the battery to the Aluminum in two separate spots and the battery terminal one on the top of the post and one in the cutout of the post as I never trusted the idea of dissimilar metal not having some resistance/ corrosion I take it you have the battery behind the Pilot not the original spot in the tail, A guy in Boonah has it in front of the Passengers feet behind the pedals.

 

 

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