Rotax 912 Ignition Problems.

[M61A1]

By "vey low" I mean less than 1 ohm. Also, it changed when wriggling the cables.

[IBob]

Dan, if you are dealing with a (partial) short or a poor ground joint, you may get all sorts of readings under different conditions.

For instance, in measuring resistance, your meter is pushing a very small amount of current at a low DC voltage through what you are measuring. Your resistance readings of the stator do look okay when measured this way, but that does not guarantee correct operation (or similar readings) in a dynamic AC situation.
 

The stator output is AC, so your meter needs to be set for AC. It will not be damaged by the AC voltage you get.

I would measure what voltage AC is coming from the stator to the ignition module/s, and I would do that with the module/s connected: this way you are seeing what the stator is doing when normally connected and under load, which is the true dynamic situation.

 

I don't know what voltage you should see: hopefully Mark, who has had a lot to do with these ignition systems, can give you some indication of that.

 

 

 

[Blueadventures]

24 minutes ago, IBob said:

Dan, if you are dealing with a (partial) short or a poor ground joint, you may get all sorts of readings under different conditions.

For instance, in measuring resistance, your meter is pushing a very small amount of current at a low DC voltage through what you are measuring. Your resistance readings of the stator do look okay when measured this way, but that does not guarantee correct operation (or similar readings) in a dynamic AC situation.
 

The stator output is AC, so your meter needs to be set for AC. It will not be damaged by the AC voltage you get.

I would measure what voltage AC is coming from the stator to the ignition module/s, and I would do that with the module/s connected: this way you are seeing what the stator is doing when normally connected and under load, which is the true dynamic situation.

 

I don't know what voltage you should see: hopefully Mark, who has had a lot to do with these ignition systems, can give you some indication of that.

 

 

 

I believe 1000rpm is 12V AC  and 2000rpm is 40V ac etc

Edited November 21, 2020 by Blueadventures

[IBob]

Blueadventures, we are needing some indication of the stator output voltages to the ignition modules at pre-start engine turnover speed.

[Blueadventures]

Understand just posting some info from my trouble shooting guide; looking forward to hearing the cause.

 

The red wires mentioned below are from the stator and 7 V is ok cranking voltage.

 

Also people have tried using a hair dryer or heat gun to warm modules and also some say placing ice (in plastic bag) on modules for 30 minutes as well ; all worth a try.

 

I carry a trouble shooting guide on board in case myself or another's rotax plays up on a trip.  Can't remember everything and its a help. 

 

Set multi-meter to AC volts, connect a probe to one red wire and other probe to ground.
For start-up RPM: ~300rpm-7v AC (all values approx)
If you have the engine running,
500rpm-12v.
1000rpm-20v,
2000rpm-40v,
3000rpm-60v,
4000rpm-80v,
5000rpm-100v.
Repeat on the other red wire.

Edited November 21, 2020 by Blueadventures

[skippydiesel]

Just a thought:

 

It seems to me that there being a sudden (no earlier/ progressive symptoms) loss of both ignition systems (fortunately on the ground), this suggests a;

common (as in one or shared) power supply or ground failure

mechanical (as in broken wire or connection malfunction)

cause most likely to be  a result of vibration/movement. (was the taxi ground rough?)

location - where wires are likely to be under compression, stretching or fretting

 

To have a sudden failure , of both ignitions, seems to be similar to the deliberate shutting down/switching of of the engine - not at all like the progressive decline, or even failure of an ignition modules performance.

 

I  apologise that this is largely a repetition of erlier advice/observation, however it is my experience that human nature seems drawn to the complex answers/solutions, when the simple one is almost starring them in the face.

[dan tonner]

Thank you all again for your further input - I am preparing a list of tests to do on my next trip to the hangar.   When I've resolved the issue I will post the solution and the final path that led to it.

M61A1  -   one amp; wiggle the wires....got it.          (What did M61A1 evolve from?)

 

Bob  -  am I correct to assume I would connect the AC voltmeter in series between one charging coil wire and its module in order to get a "dynamic" reading while cranking on battery?

(I note Blueadventures appears to do these checks with the meter between the coil lead and ground whether cranking or during an engine run on one mag while the other is being tested.....unless there's another way to make it turn at 5000 RPM...🙂) 

 

Skippydiesel:  I am still hoping that "simple" solution might involve removing a dead rat from my exhaust.

 

All the best to each and all;

CanadaDan

[IBob]

Hi Dan, no the meter does not want to be in series with the circuit. The circuit needs to be connected up as normal, and you are 'sampling' the VAC reading at the one point on the circuit with one probe of the meter. The other probe goes to ground.

 

You may be able to get the meter + probe into the connector that connects the stator and the ignition module in order to do this. If not, you will have to attach a short temporary wire somehow at that point so that you can attach your probe, while still having the stator connected to the ignition module in the usual way.

 

With the meter connected in this manner, crank the engine, and you will get  VAC reading of what voltage the stator is passing to the ignition module/s for startup.

 

I'm hopeful Mark may be able to give us a value to compare this to.

 

And it may well be that Mark has more to add to this: he has the experience.

[Blueadventures]

2 minutes ago, IBob said:

Hi Dan, no the meter does not want to be in series with the circuit. The circuit needs to be connected up as normal, and you are 'sampling' the VAC reading at the one point on the circuit with one probe of the meter. The other probe goes to ground.

 

You may be able to get the meter + probe into the connector that connects the stator and the ignition module in order to do this. If not, you will have to attach a short temporary wire somehow at that point so that you can attach your probe, while still having the stator connected to the ignition module in the usual way.

 

With the meter connected in this manner, crank the engine, and you will get  VAC reading of what voltage the stator is passing to the ignition module/s for startup.

 

I'm hopeful Mark may be able to give us a value to compare this to.

 

And it may well be that Mark has more to add to this: he has the experience.

For while running checks attach a suitable sharp pin to the multi-meter probes and insert carefully under the grommets on  the pin in the connectors (so you don't damage anything, also don't insert through the grommet, its there for water and dust proofness.  later I'll take an image of my spark tester, home made many years ago and has an adjustable gap so you can see the spark and its intensity, got to jump the gap; if you want an idea to make one.

[IBob]

3 hours ago, Blueadventures said:

Understand just posting some info from my trouble shooting guide; looking forward to hearing the cause.

 

The red wires mentioned below are from the stator and 7 V is ok cranking voltage.

 

Also people have tried using a hair dryer or heat gun to warm modules and also some say placing ice (in plastic bag) on modules for 30 minutes as well ; all worth a try.

 

I carry a trouble shooting guide on board in case myself or another's rotax plays up on a trip.  Can't remember everything and its a help. 

 

Set multi-meter to AC volts, connect a probe to one red wire and other probe to ground.
For start-up RPM: ~300rpm-7v AC (all values approx)
If you have the engine running,
500rpm-12v.
1000rpm-20v,
2000rpm-40v,
3000rpm-60v,
4000rpm-80v,
5000rpm-100v.
Repeat on the other red wire.

Sorry, Blueadventures, I missed your earlier post.

Just to be quite clear: are the quoted voltages (For start-up RPM: ~300rpm-7v AC ) for the part/s of the stator that feeds to the ignition module/s?

[Blueadventures]

24 minutes ago, IBob said:

Sorry, Blueadventures, I missed your earlier post.

Just to be quite clear: are the quoted voltages (For start-up RPM: ~300rpm-7v AC ) for the part/s of the stator that feeds to the ignition module/s?

No worries,  Yes the reds (there are 2) that go into the 6 pin connector assembly from the stator.   Not any of the reds at the rec / regulator. 

 

These will be shown in chapter 74 of the Rotax heavy maintenance manual.   I am guessing he has a 912 ULS maybe model 2.

 

This check will verify correct voltage be produced.

 

I have not had an issue with Rotax 912's like this so keen to hear his remedy.   (I have a summary of checks to fault find and some spares to hopefully always get going in a safe manner when the situations arise.  This great site of Ians allows for assistance and learning about aviation things by those willing to join the site and share and participate.

Edited November 22, 2020 by Blueadventures

[skippydiesel]

2 hours ago, dan tonner said:

T....................................................

 

Skippydiesel:  I am still hoping that "simple" solution might involve removing a dead rat from my exhaust.

 

All the best to each and all;

CanadaDan

Unfortunately dead rate or exhaust blockages from anything douth not, a failure to spark, make.

[dan tonner]

Blueadventures.....

 

....My engine is a 1997 912 UL - The connection at each module involves 9 wires as follows:

1. one 4-pin plastic connector (feeds from the 2 trigger coils that feed that module),

2. a bullet-style connector for the module's mag switch,

3. a bullet-style connector for the charging wire from the stator,

3. two bullet-style connectors which feed signals from that module to its pair of sparkplug coils,

4. a black wire ground for the module which is tipped with a ring connector.

 

NOTES:

1.   My sparkplug coils ground directly onto the 1 / 3 intake manifold on the engine - on newer versions, these ground wires feed back into the modules.

2.   My serial number is 4401811 - this engine was included in group A of the Service Bulletin  912-026 (December 1999) dealing with stators whose leads which were subject to insulation failure.  I have just learned how to examine the wiring to determine whether or not the stator on this engine was replaced as mandated in the bulletin.  The change was to have been done "at the latest" buy April of 2000.

3. There doen't seem to be a completely accurate diagram of my ignition setup in the latest version of the Heavy Maintenance Manual. 

• Fig. 74-18 on page 25 of 74-00-00 purports  to be the "old style" UL version but shows the sparkplug coil ground wires  feeding back into the module. The module/ sparkplug coil / sparkplug  assignment is like mine.
• Fig. 74- 21 on page 31 of 74-00-00 illustrates the "older style" 914 UL/F version.  Although the sparkplug coil grounds are shown converging to a single engine groundpoint, the module / sparkplug coil / sparkplug assignment is specific to the 914's and not the 912's.

 

 

 

 

 

 

[waraton]

On a slightly different matter, where can I get the 6 pin connector assembly for the regulator???? 

[IBob]

PS Dan: you asked  while back what would happen if there was some shorting between the two stator wires that go to the two ignition modules.

What they are supplying is AC (frequency obviously depending on RPM).

IF the two stator coils connected to those two wires respectively are positioned so that their AC outputs are out of phase: then the two AC waveforms would tend to cancel each other out, with little or no power going to the ignition modules.

 

[Blueadventures]

1 hour ago, dan tonner said:

Blueadventures.....

 

....My engine is a 1997 912 UL - The connection at each module involves 9 wires as follows:

1. one 4-pin plastic connector (feeds from the 2 trigger coils that feed that module),

2. a bullet-style connector for the module's mag switch,

3. a bullet-style connector for the charging wire from the stator,

3. two bullet-style connectors which feed signals from that module to its pair of sparkplug coils,

4. a black wire ground for the module which is tipped with a ring connector.

 

NOTES:

1.   My sparkplug coils ground directly onto the 1 / 3 intake manifold on the engine - on newer versions, these ground wires feed back into the modules.

2.   My serial number is 4401811 - this engine was included in group A of the Service Bulletin  912-026 (December 1999) dealing with stators whose leads which were subject to insulation failure.  I have just learned how to examine the wiring to determine whether or not the stator on this engine was replaced as mandated in the bulletin.  The change was to have been done "at the latest" buy April of 2000.

3. There doen't seem to be a completely accurate diagram of my ignition setup in the latest version of the Heavy Maintenance Manual. 

• Fig. 74-18 on page 25 of 74-00-00 purports  to be the "old style" UL version but shows the sparkplug coil ground wires  feeding back into the module. The module/ sparkplug coil / sparkplug  assignment is like mine.
• Fig. 74- 21 on page 31 of 74-00-00 illustrates the "older style" 914 UL/F version.  Although the sparkplug coil grounds are shown converging to a single engine groundpoint, the module / sparkplug coil / sparkplug assignment is specific to the 914's and not the 912's.

 

 

 

 

 

 

Dan I'll have to look up tonight.  In the meantime look for the the two charging wires coming from the stator in the diagram they are red (ro) and will go to the connector for the coil units.  This will be the wires to measure at.

[Blueadventures]

1 hour ago, waraton said:

On a slightly different matter, where can I get the 6 pin connector assembly for the regulator???? 

Bert Flood will sell and about $280 plus postage.

[M61A1]

4 hours ago, dan tonner said:

M61A1  -   one amp; wiggle the wires....got it.

That's 1 ohm (resistance) one other check also would be to put the meter on one of the cables at a time and the the other meter probe on the engine.

That will tell you if they are shorted to the cases.

[Kyle Communications]

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 then the AC volts you will measure with a Digital multimeter and the AC volts peak to peak you would measure on a CRO which of course is the real voltage as the multimeter will only read the RMS and be somewhat lower due to the wave shape of the pulse

Maybe 300RPM is what your starter will swing the engine over at so you should see some voltage on the Red wires coming from the generator

Make sure you have the red wires disconnected from the CDI this will be fine to test the voltages by just winding the starter over without any danger of the engine firing. Most likely the voltage will be slightly different when connected to the CDI as therewill be a loading effect....I used a Fluke multimeter and a Siglent 200mhz CRO

 

 

 

RPM          METER      CRO

300           5.4V           20V

520           9.2V           40V

800           14V             60V

1000          18.5V          80V

2000          34.5V         150V

3000          50V            200V

4000          66V            300V

 

 

[Kyle Communications]

Sorry Mike I didnt see your previous post on the voltages. 

[M61A1]

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....still no spark.

Edited November 22, 2020 by M61A1

[Yenn]

Do you have a wiring diagram for the engine?

I have a one page diagram in my 2000 edition of CPS catalogue, which seems to corelate to what you say you have. If necessary I could copy and paste it here I think.

It looks to me that you should have4 earth wires coming from the modules to combine into 1 wire to earth. A failure in the single piece of wire would result n all ignitions being dead. I have no experience of Rotax maintenance, but will have a look at all the posts here to see if I can spot another failure point.

It certainly appears to be electrical rather than fuel related.

[onetrack]

Waraton - you might like to check out the thread below. You can buy all types of connectors (plugs and spades and bayonet connectors) from Alanco or Ashdown-Ingram.

 

That means you basically have to build your connector yourself.

 

https://www.sportpilottalk.com/viewtopic.php?t=4682

[Blueadventures]

47 minutes ago, Kyle Communications said:

Sorry Mike I didnt see your previous post on the voltages. 

All good, mate.  No worries good to hear you were at the hangar.  Thanks for your info.  Cheers Mike

[Yenn]

Further reading of your posts does not let anything jump out at me. You say you tested the mag switches and they were good. Was this test done from the single pole connectors to ground or just across the switches?

Have you checked the continuity from the 4 single connectors between the modules and earth? I would expect if that is your problem that all 4 would be open circuit, if one was OK you should get some spark.

It would take both circuits in the magneto generator to fail together to produce the symptoms you have. I assume earlier tests of the ignition did not result in one failing.

Sorry I can't point to an obvious failure point, but I am not a Rotax expert. I hope I have given you some help.