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Both ignitions fail?

I have about 55 hours on my -12 and due to moving and a medical problem had not used it for about 4 months. It was not happy on starting but did get there after about 10 minutes of trying. I taxied to the runup area, about 3,000' and as I braked to a stop the engine died. It would not restart and I towed it back to the hangar. Checked the fuel flow all the way to each carb and it is fine but both ignitions are dead, no spark on either side. I do not see anything in the schematic or the wiring diagram for a single point of failure. The engine was supplied in 2012 and does have the soft start. So far I have not found the cause of the failure. Nice that it died at the beginning of the runway and NOT at the far end. :)
 
Thanks John,
Plane was "resting" inside a metal hangar, quite low humidity but it was cold at times. The puzzle is both ignitions? Every else, Skyview, avionics & transponder all OK but there was a fuse on the autopilot that had died and did not light up.
Henry
 
First thing I would check - -

Take the mag ground wires apart at the connections under cowl and use a VOM to check if the mag grounds are working. Mag switch ON should test open circuit. OFF, strong continuity.
 
Take the mag ground wires apart at the connections under cowl and use a VOM to check if the mag grounds are working. Mag switch ON should test open circuit. OFF, strong continuity.

And then check the gascolator and float bowls for water.

And then try some fresh fuel.
 
What seems really weird is that it started and then apparently both ignitions failed within a few minutes. I hope you post what you find.
 
I did have the auto pilot fuse open with NO light on the fuse so I replaced all the fuses and also checked their continuity, all around 0.2 ohms. Fresh fuel has been mentioned but I did check fuel flow at the carb inlet and it is hard to believe that BOTH carbs would fail at the same time.
I will check the igniter circuits as suggested and report the progress, or lack of.
Tomorrow is supposed to be cold and windy, it may not be worked on before Wednesday.
Henry
 
Henry,

I've been thinking about your problem (I love puzzles!) please dont be upset with me asking this, but are you ABSOLUTELY SURE you are getting no spark? How did you come to that conclusion? I ask because the probability of those two systems both failing is very minute.

The hard start and subsequent engine stoppage on reducing throttle to stop at runup area point very strongly to a fuel problem rather than ignition. You did not say what type of fuel you are using. If you're using mogas there is a possibilty that after 4 months of sitting it has deteriorated and the carbs are getting gummed up internally. Just because there is flow to the carbs does not mean they are clear inside. This is one of the downsides to using mogas.

Suggest you confirm that there is really no spark as your next step.

John
 
Since you have checked the fuel flow, it seems that you are not sure that both ignition systems have failed. The chances of both ignition systems failing at the same time are about the same as the chances of winning the lottery. There is not much in common with the two ignitions, maybe a common ground point on the engine? The only other thing in common is the spinning flywheel with permanent magnets.
The engine quitting after taxiing 3000 feet is consistent with a fuel problem. The engine runs until the fuel in carburetor bowls is exhausted. Could there be ice in the fuel system, maybe in the carburetors?
 
There is not much in common with the two ignitions, maybe a common ground point on the engine?

Actually, even that is redundant with a separate bolt used for each ground connection.

The very hard starting after 4 months of storage, coupled with sudden stoppage is what tricked me into a quick conclusion of a fuel problem.

I agree that a dual failure of the ign systems is highly unlikely.
 
Are you sure both ignitions were firing when you started and taxied? It's possible one had failed before the engine started and the other failed later. Until you do the ignition check at run up you can't know that both or just one are firing.
 
I totally agree that it should be easier to win the lottery than have both ignitions fail at about the same time. that's why I posted the problem here, in case I had forgotten something simple. I checked the front left plug and it was clean and a little damp. I put the plug back in the cylinder but connected a spare pair of plugs to the leads of the front pair of cylinders and grounded the plug bodies. Crank the engine over and no spark at either cylinder.
Today it is not only cold but it is snowing! Will report back tomorrow on the ignition switch leads at the switches. It would be easier to check at the "weather pack"? plugs on the modules themselves but they are hard to take apart.
Henry
 
Interesting

I have no aircraft engine experience but I learned a long time ago to begin the search for the fault with the most obvious 'sign or symptom' and work from there towards the solution. Looks like you have no spark so start at the plugs and work towards the spark generator, etc., etc., etc.

I'd also replace all of the fuel from your aircraft if it is old. Good skill to you.
 
The only way to disable the ignition wires is to short them to ground. A broken wire that is not touching ground will not stop the engine. The chance of both ignition switches failing in the closed position while the engine is running is infinitesimal. The definition of infinitesimal is the distance that an aircraft carrier sinks in the water when a fly lands on its deck. :D
 
I’ll throw some wood on the fire… the Rotax 912 has capacitive discharge ignition. The ignition is powered not by the battery but by a separate set of coils within the alternator windings at the flywheel. That said, the engine must spin ~ 500 RPM to generate enough voltage to self-power the ignition. Speeds below ~ 500 RPM will not produce a enough voltage to operate the CD ignition.

My suggestion for troubleshooting is to remove at least one plug from each cylinder to allow faster cranking speed of the engine. Then connect a known good plug to one of the high-tension leads and ground the plug to the cylinder head. Engine should crank at higher speed and spark should be produced by CD ignition. You should use a brand new plug for this test. Slight wetting of the plug will allow a path to ground and no visible spark.
 
Jim,

I used to believe that the ROTAX required a high RPM to power the CDI, but then I saw a YouTube video of a guy who hand propped a 912. Now I'm not so sure.

Rich
 
I just searched and found the YouTube that shows a guy hand propping a 912. I guess its possible to flip the prop fast enough to generate the required voltage for the CD ignition. Actually makes sense when you back drive the 2.43:1 gearbox the prop only needs to turn 200 RPM to get 500 RPM at the engine.

Still not recommended?
 
I just searched and found the YouTube that shows a guy hand propping a 912. I guess its possible to flip the prop fast enough to generate the required voltage for the CD ignition. Actually makes sense when you back drive the 2.43:1 gearbox the prop only needs to turn 200 RPM to get 500 RPM at the engine.

Still not recommended?

I believe that is the 85HP 912 which doesn't have the high compression ratio that the 100HP has.
 
So far no progress. The health problem that kept me out of the air for 4 months has struck again and I have not been able to get to the hangar. Hopefully some time this coming week I will check both of the ignition switches. I will post whatever I find even if is gives me a red face. :)
Pure speculation, from not being able to do anything else. If one ignition had failed, hence the hard starting, and the other failed near the end of the runway it COULD account for the symptoms. Same cause? maybe.
Henry
 
Was able to make a quick check today on the two white wires at the ignition modules. Each wire reads about 0.2 ohms to ground regardless of the respective switch position, i.e. ON or OFF. Not surprising that there is no spark! According to the schematic these two wires change color at an Amp connector prior to going to the switch module. I will track them down tomorrow.
Henry
 
Those two white ignition wires are coaxial cables that are spliced on the engine side of the firewall. That splice is a good place to start troubleshooting. Earlier models used 1/4" spade connectors. Later models use a 3 pin Amp connector. Separate the connector and check that there is no continuity between the coax center conductor and ground on each half of the connector. And make sure the coax shield is not close to touching the center conductor at the connector. The shield is not spliced at that location.
 
Unhook both ends of those cables Joe is talking about. Then check for shorts between center conductor and shield. If they are shorted examine entire length carefully to see if they have been pinched at some point.
 
About 6 months ago I was called to get a CT with a 912 running.It sat for months without being started and would run and die within 10 seconds or so.
Initially thoughts were that it had a fuel problem.Put fresh gas in,disassembled carbs,no problems found.Then it wouldn't fire at all because of no spark:checked grounds,kill switch,etc.No spark from either system.Sent both boxes to Lockwood for testing and was informed both were bad.Two new boxes,and its been running fine.Must have been that lottery thing.The owner could have used a lottery win to pay the bill for 2 boxes.
 
Thanks for the information on two modules failing almost at once. There are similar reports on the Rotax forum. There they also claim that the starter may be at fault for not delivering enough cranking speed and/or the modules needed to warm up. Not the case here as the engine was running and the oil temp. was at 110 degrees. Today I rechecked the two white wires with the panel cover removed and dsub disconnected from the switch module and all was OK. reconnected the switch dsub and all was still OK but no spark. One odd thing, when the engine died a week back the auto pilot fuse had blown. Today when cranking the auto pilot fuse blew again. It did light up this time though. Could these two events be connected in some way? I will trouble shoot further but it is looking like I am in for something over $2,000.00 for two new modules with less than 60 hours on the engine. The engine came from Vans in early 2012.
Any additional thoughts?
Thanks
Henry
 
Weak battery??? Might be a longshot but could be a possibility. Maybe check that the battery is charged.
 
It really doesn't take that much cranking speed to make a spark with a 912,or a 582 for that matter.I have hand propped both numerous times with a low battery.And the ignition systems are electrically totally separate from the 12 volt side of things,other than being wound on the same stator assembly.
 
Could these two events be connected in some way?

Yes.

When the buss voltage drops below nominal, the current to operate a device goes up (basic ohms law)

The voltage drop you are causing while cranking could cause a fuse to blow.

Have you put on a battery charger and fully charged the battery after all of this cranking began?

Did you do so before starting the engine after it had sat unused for 4 months?

In my opinion ordering new ign. modules based on a couple of claimed instances of dual failures mentioned on an internet forum would not be a good idea. Spending even a couple hundred $ to have a Rotax trained tech look at it and fully troubleshoot the problem to a confirmed cause could save you many hundreds more.
 
Yes.

When the buss voltage drops below nominal, the current to operate a device goes up (basic ohms law)

The voltage drop you are causing while cranking could cause a fuse to blow.

Have you put on a battery charger and fully charged the battery after all of this cranking began?

Did you do so before starting the engine after it had sat unused for 4 months?

In my opinion ordering new ign. modules based on a couple of claimed instances of dual failures mentioned on an internet forum would not be a good idea. Spending even a couple hundred $ to have a Rotax trained tech look at it and fully troubleshoot the problem to a confirmed cause could save you many hundreds more.

I had a battery that was showing 12.5 volts and dropping to 6 during cranking. It developed that problem the odysseys get using a trickle charger.

A new battery solved everything.

You might also want to check for the cabin heater cable possibly shorting the starter. Also, maybe the ground on the starter modules that we install as part of the engine section?

BTW, you can buy that battery at any Batteries Plus location, a lot of motorcycle dealers/repair shops.
 
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I vaguely remember a thread on broken mounting brackets for the ignition modules and the impact this has on losing the module ground as opposed to the P-lead ground. Are your module mounting brackets intact?
 
I vaguely remember a thread on broken mounting brackets for the ignition modules and the impact this has on losing the module ground as opposed to the P-lead ground. Are your module mounting brackets intact?

I don't think there is a module ground as far as I can remember. The module housing is in plastic and is insulated by the rubber dampers on which the bracket is secured. There is a separate ground wire which is not affected by the mounting bracket failure.
 
I had a battery that was showing 12.5 volts and dropping to 6 during cranking. It developed that problem the odysseys get using a trickle charger.

A new battery solved everything.

You might also want to check for the cabin heater cable possibly shorting the starter. Also, maybe the ground on the starter modules that we install as part of the engine section?

BTW, you can buy that battery at any Batteries Plus location, a lot of motorcycle dealers/repair shops.

I have friends with a Rotax engine.

They have found the same problem/solution as mention here.

A weak battery. It will turn/crank and you think that it should but the strength of the battery MUST be up to snuff.

Easy thing to try.

James
 
The test worked, will try a message.

The medical situation has cooled down so back to the RV-12.
Although the engine seemed to spin over just fine with the old battery I did a load test on it. At 50 amps it was down to 9 volts. As a poster noted, at low voltage the servos would draw higher current, that solves the fuses blowing situation. A new PC 680 battery ( from 4 wheel Parts it was $96 compared to $156 from Battery Mart! and $117 from AS&S) seems to have solved the starting problem. Less than two revs. and it fires right up with no problems.
I have started and stopped the engine at least 10 times so far, again with no problems.
I still find it hard to believe that the 912 can be hand propped but not start when the engine turns over quite well, also no sign of a spark with the old battery. The old battery was only three years old with less than 60+ flight hours on it. I did use a trickle charger a few times but I now find that was not a good idea.
Thanks for all the help, a couple of posters got it right!
Henry
 
at the beginning of this thread it was stated that the ''engine died''. which means it went from running to won't run. if it does that on the ground what is to prevent the same situation in the air? batteries do go bad in the air.
 
With most BOX type ignitiions systems, be it newer lawnmower, marine, car.....the ecm needs to see a threshold voltage > 9 ish volts to operate, a lot of times you may have the RPM but the cranking voltage drops below this critical voltage and the sparkey part wont work.
 
at the beginning of this thread it was stated that the ''engine died''. which means it went from running to won't run. if it does that on the ground what is to prevent the same situation in the air? batteries do go bad in the air.

if the battery was in bad shape, ( alternator weak and failing ) and if there was any load on the aircraft, lights, fuel pump, Dynon, when the RPM came to idle and the voltage dropped, engine go Kaput.
 
The capacitive discharge CD ignitions on the 912 have a separate coil to generate their own operating voltage. This is completely independent of the main 12 VDC battery. As far as engine ignition is concerned the main battery is only needed to spin the engine fast enough for the CD units to self-generate their own voltages. Once the engine is running the main battery is out of the equation and could even be removed (or go dead) and not effect either ignition. As long as the engine is spinning fast enough ? you have spark.
 
A new PC 680 battery ( from 4 wheel Parts it was $96 compared to $156 from Battery Mart! and $117 from AS&S)

This part got my attention, and probably some others here as well - we can always use a cheaper source for our parts - do you have a link for this place?

EDIT - found it, with only my mediocre (at best) Google-Fu skills. Looks like the right one, and the price is the best I've seen so far.

http://www.4wheelparts.com/Electrical/Extreme-Powersport-Battery.aspx?t_c=72&t_s=12&t_pt=4219&t_pn=ODYPC680
 
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