Ignition Gremlin

[Av8r3400]

As I alluded in the "Milestone (http://www.teamkitfox.com/Forums/showthread.php?t=6601)" thread, I have been chasing an ignition problem in the Mangy Fox ever since the first start. Because of this, the flight testing has been put on hold.

Here is a description of the problem:

On doing the run-up to 4000 rpm, testing one ignition (A) will drop about 50 rpm. Perfect.

Testing the other ignition (B) gives ~500 rpm drop and the EGTs (located on cylinders 3 & 4) quickly climb through 1500º! Not so perfect.

I have done all the usual stuff.

Cleaned all grounds
Checked firing order
Cut the tips off the plug wires and inspected boots
New Plugs Gapped to .027"
Removed modules and checked wiring
Removed, cleaned, rebuilt, synchronized carburetors
Then I did it all again...


I spent time today speaking with tech support with CPS, LEAF and Lockwood. The guys at Lockwood cam up with the theory (and they have seen this before) that one of the modules is malfunctioning and could be firing one side 180º off. This would cause the problem I'm seeing.

Each module fires a coil every 180º of crank rotation and each coil fires a pair of plugs (1 & 2 top, 3 & 4 bottom, etc.). If the module is malfunctioning and firing both coils at the same point, then one pair of plugs will ignite the fuel on the way out the exhaust valve, causing the EGTs to skyrocket.

[Av8r3400]

I sent the modules off to Lockwood today to have them tested. (Lockwood is the only place in the US with the testing machine for them)

I have mixed feelings on this. If the module is bad, it will cost me $1200 for new one. If the modules are good then I've got absolutely no clue what's wrong. (But I'll still have money in my account) That's either a win-win or a lose-lose, I'm not sure...



I've heard that kidneys are selling for about $1500 these days. :confused:

[HighWing]

"Checked firing Order". Not sure what this means. Would this check have detected the 120 degree off Lockwood is suspecting? The first thing that came to my mind is the possibility that the 1 - 3 or the 2 - 4 lower plug wires might have been switched. Do you have the yellow tags on the ignition wires?

[WWhunter]

Not sure if this makes much differnce, but I thought the plug gap was supposed to be set around 0.021". I need to go check my Zipper plugs I guess.

I just seem to recall there was a 'tighter' gap with one of the piston sets. I do recall the 95 HP Extra-Performance pistons suggested a smaller gap than factory.

[Av8r3400]

When I say check the firing order, I mean the routing of the plug wires to the proper coil. That also means checking that the coils were wired properly to the correct ignition module wires and the plugs were hooked to the proper coils. Thus eliminating the possibility of 1/3 and 2/4 wire mix ups.

Rotax calls for .028" gap on plugs.

[WWhunter]

Yes sir, it was the plugs on the 912 XtraPerformance pistons I originally had in the motor that needed a smaller gap.
www.craftworks.biz/pistonsite/6318.htm

[Av8r3400]

It's a Good news - Bad news situation today.

Good news is that the modules checked out fine down at Lockwood. :)

Bad news is now I have no idea what the problem is… :confused:

[gregsgt]

The EGT climb doesn't make sense to me. Dropping a mag should make the mixture more rich and EGT's climb when the mixture gets lean...

I think it sounds like a wiring problem in the ignition somewhere. Maybe a bad switch or something.

[Slyfox]

this is my thoughts. when you get your modules back, switch sides, see if it changes to the other side, if not, electrical wiring

[Dave S]

Larry,

Don't know if this would help any; but, on single ignition engines timing can drastically affect RPM. If everything else is equal (thottle the same) advanced timing will result in a higher RPM......retarded timing will result in a lower RPM...retarded timing taken to the extreme (short of killing the engine) can also result in a big RPM reduction with the charge burning partially on the way out of the engine which would possibly raise the EGT.

When you mentioned 50 and 500.....the 50 almost seems like less of a drop than a person would normally get on Rotax. If considering timing....is there any chance that the side which drops off 500 and raises the EGT is running on a severely retarded timing setting?

I don't have a clue how timing is controlled on a Rotax. Don't recall if you have the soft start (which I believe retards the timing to prevent kickback) and I don't have any idea if there is any possibility of the soft start affecting the running mode.

Again, not saying that I know anything about what the problem is; but, thought I wanted to share this possibility in case it might play into the issue.

Wish you luck in solving this.

Dave S

[Av8r3400]

These are all good ideas and I thank you for all of them!

I should be getting my modules back tomorrow and further testing will commence as time allows.

(Dam day job getting in the way of my flying fun time... :mad: )

[Av8r3400]

The ignition problem has been found.

After hours of testing and cross checking, re-testing and re-cross checking, the modules were finally found to be the culprit. Even though I had sent them both down to Lockwood for "testing" and they told me they were good. I found out later, that Lockwood can only test for function, not for "proper" function.

I believe there is a ground fault in both of the modules which cross feeds back and forth, but only when one of the two modules is shut off. I tried replacing each of the modules one at a time and the problem persisted until both were replaced. When they are both "on" they seem to function properly (but I didn't trust them).

What to do? Well, both modules need to be replaced. Yes, that hurt$. A lot. The modules on my engine are referred to as 4x1 modules, because they have a 4-pole plug and several single wires. These (of course) are the most expensive modules available because they are the oldest design (mid 90s). The latest model module is over $300 cheaper, but they come with 2 6-pole (6x2) plugs. So the guys at Lockwood were nice enough to include a parts list for all of the little "bits" to convert to the 6x2 module, which also includes the factory soft start feature. Now, even with all of the little bits, the conversion is still several hundred dollars less expensive than going with the original modules AND they are available off the shelf where the others would have to be ordered from Europe. (Where apparently there is some little guy, locked in a closet, who makes these things one at a time…)

So, today I took the (very) painful step in ordering these parts from LEAF. I will post more details when I have the parts in hand and do the conversion.

[Dick B in KY]

Larry, I feel your pain. Had to replace both modules on my 912ULS a couple years ago. Could not get them in the US, so had to get from Rotax Canada, about 1400.00. Good luck.

Dick B

[avidflyer]

Dick B. You mentioned Rotax Canada in your post, and I was wondering about prices on rotax parts from them. The Canadian dollar is now about .75 compared to the American dollar. I wouldn't think the parts in Canada all went up by 25% when The value of the US dollar went this high. The Euro is way down compared to the US dollar, close to 25% in the last 5 years (1.40 -1 then and now about 1.1-1) That alone should have caused the prices we are paying for Rotax parts to go down, being as how they come from Austria. I suppose Rotax is just gouging US customers for that much more now. Jim Chuk

[DesertFox4]

Hoping that this gets you back in the air. Others may need to go through this conversion process if their older modules go the way yours went. Good luck.

[Av8r3400]

The job is done! We are back in business with the engine running excellent!!


The conversion went fairly easily with the help of the wiring diagram in the heavy maintenance manual.

Here is the list of part numbers I used to convert my engine from the "old" style 4x1-pin modules to the new 6x6-pin modules.

2 - 965-444 6x6 CDI Modules
1 - 853-125 Connector Bracket
2 - 265-265 Connector Housing
2 - 265-269 Connector Housing
12 - 265-210 Connector Pins
12 - 265-275 Connector Sockets
24 - 260-130 Cable Grommets

The connector pins and sockets are the "guts" to the weatherproof plugs. They absolutely require the proper crimper tool to attach the wire. See the photo of the crimper jaws below. This isn't a regular crimper it makes a "B" shaped double crimp to the wire and the other circular jaw closes the pin around the weather proof grommet.

The other photo is of the finished installation. As you can see, many of the wires needed to be extended. The ground and power wires going to the coils needed to be extended. This was required mostly because of where I have the modules located on the engine mount rather than the OEM location on the engine itself. The "connector bracket" listed above is a metal bracket that holds the plugs steady all but eliminating the possibility of the wiggling wire breakage problem we all have heard of or experienced.

You can also see that I am a huge fan of labeling everything. All of the coils and their leads are labeled to show what they are and where they need to go. This was partially due to the testing and diagnosis exercises I was doing, but it also proved very necessary during the conversion wiring. You'll wind up with a ton of spaghetti and this can easily get messed up and hooked up wrong.

[Dave S]

Hi Larry,

Glad this worked out for you. A good reference for others in the future.

A couple observations about the good procedures you have used in your wiring.

1) Marking....this is a big deal...each of us needs to remember that one so when we need to dig into a circuit down the road....we can know what is what. One of my constant companions in the hangar is a sharpie.....good for marking what goes where, dating replacement parts and recording frequently used things like torque, spark plug gap,etc right on the engine where it is easily found.

2) Securements....I see that you have tied down & bundles wires so they don't flop around - good for everyone to remember. One of the EAA Tech Counselors in our chapter put it this way....."Design your wired securements like a good bra....the idea is to lift, separate and immobilize";)

Dave S

[WWhunter]

Did you have to essentially build a new wiring harness also?
I had issues with mine when I first bought the plane and even though I fixed several 'breaks' in the wiring, I have never felt 100% confident in its durability. When repairing the breaks, I was quite surprised at the bad quality of the wire.

My thoughts lately have been to reconstruct a new harness out of better quality wiring.

[Av8r3400]

I really didn't build an entire new harness. I did extend the low voltage coil wires both hot and ground to properly connect them using the bracket. I did also need to extend the red power wires off the stator and the switched ground wires, again to reach where I wanted to mount the plugs.

The new modules have much more flexible and higher quality wires.

[Jorket]

Is this ignition problem typical? I'm facing very similar issue...

[Av8r3400]

From what I was told by every Rotax tech and expert I spoke to, this is extremely rare. Modules are usually like light bulbs, either they work or they don't.

Describe the problem you are having. I've become a reluctant ignition expert in my own right…

[Paul Z]

Have you checked trigger coil gaps? They can make it idle poorly.
The trigger coils activate the spark plugs. I believe the spark plug gap should be .022 to .035. According to both Ronnie Smith & Eric Tucker Maintenance & Heavy Maintence Trainers it is better to set the Spark club gap at the low end, or .022. The trigger coil gaps depend on the style of trigger coil you have. If you have the "old Style" the gap should be .016 to .022, for the trigger coils with clamps the Gap should .012 to .016. According to Bryan Toepfer (CPS), Ronnie Smith & Eric Tucker, they should always be checked before putting an engine back in because they can move.

[Dusty]

Trigger coil gaps?
How are these adjusted? There appears to be no movement available,do the brackets need to be bent:eek:
I have been having some problems, 6 partial failures resulting in 2 forced landings. We can't reproduce these failures on the ground.
Testing found one broken wire.Out of desperation I have replaced the stator,pickups and modules with low time items that are known to be good.
The modules are now mounted on the cabin side of the firewall,the red stator wires and pickup wires are long enough to reach comfortably(and almost in the centreline of the dynafocal mount,so movement shouldn't be such a problem)
The wiring to the coils will be extended,hopefully an uneventful test flight will happen in the next few days.
As a side note my IVO had one blade 11grams lighter than the other two.
This definitely wouldn't help the wiring and may have been upsetting the carbs
But the problem was showing up on climb out on the 2nd or 3rd circuit.
Am I missing something?

[Av8r3400]

Dusty, what is the engine doing during the failure?

Does it quit completely or run rough or what?

Which wire was Broken?

[Dusty]

The engine appears to drop two cylinders randomly,sometimes for a second or two, sometimes longer, it can do it multiple times in succession or once then be good for a while(I havn't had a chance to look at the egt when this is happening)
The broken wire was on a pickup/trigger.
The stater had a repaired wire,we had a possible intermittent reading on this but even with wiggling/tugging it was inconclusive.
Starting is excellent but idle isn't as smooth as other 912's on our field.
The carbs have been overhauled and rechecked.

[Av8r3400]

Since the ignitions are split, I would question how it could drop two cylinders completely. Look over the grounding leads going to the coils very, very carefully. Mine were grounded in pairs which could lead to two coils not firing at the same time, making the possibility of dropping two complete cylinders. However, I don't think the engine will continue to run with two cylinders not firing at all.

I added redundant grounding because I found all of my grounds went to the same point on the ignition system. That worried me in that if that one wire broke, the motor would shut down. The coils were grounded in pairs to that point. Now that single ground buss has redundant wires grounding it to the airframe.

Has your stator been replaced since that service bulletin came out?

[Paul Z]

Trigger coil gaps?
How are these adjusted? There appears to be no movement available

It is covered in the Heavy Maintenance Manual but not very well, there are two screws with each trigger coil. It is sort of like adjusting points on an old car. Get the feeler gage (preferably brass feelers) and slide it between the trigger coil & the flywheel, loosen the scores on the trigger coils and adjust it until you can feel resistance on the feeler gage. Repeat the process for all 4 trigger coils. According to Brian at CPS he has found trigger coils out of adjustment relative to the gape on new engines out of the crate.

[Paul Z]

Since the ignitions are split, I would question how it could drop two cylinders completely.

Each Trigger coil controls 2 cylinders. Go look in the Heavy Maintenance Manual Chapter 74-00-00 page 20. It shows the 4 trigger coils B 3/4, A1/2 A3/4, & B1/2. The Trigger Coils A1/2 & A2/3 control the top plugs, B1/2 & B 3/4 control the bottom, see Chapter 74-00-00 page 19. I would Ohm out the ground & trigger coils to see if I could isolate the fault.

[Dusty]

The stator was changed a few years back.
I will get a recheck on the earth wiring,we did add a separate earth.
The pickup/triggers were the early type,these have been binned.
I'm not much good on electrics,I hope to have this sorted soon
Thanks for the help

[Paul Z]

Have you checked the gap on the trigger coils?

[Dusty]

I havn't checked the trigger coil gap,they have been replaced with the later type.
We didn't realise at the time they were adjustable:eek:
The engine hasn't been run since then.
My engine also has the paired earth wires on the coils,this will be changed.

[mr bill]

The old style coils were not adjustable, but the new ones are.

[Paul Z]

According to the Heavy Maintenance Mannual both the old and the new are adjustable. 74-00-00 page 50 shows the potted style, while page 51 shows the newer style. I have never seen or worked on the old ones, but I'd at least check the gap.

[Av8r3400]

If you look on page 47 of chapter 74 in the Heavy Maintenance manual you will see that the "old" style are not slotted or really adjustable.


The old style pickups should be .016-.020" (.4-.5mm), the new should be .012-.016" (.3-.4mm).

[ref Chapter 74, page 62 Heavy Maint. Manual (http://flyrotax.com/portaldata/5/dokus/d06155.pdf)]

[Paul Z]

Good luck.

[Dusty]

Thanks for the link for the maintenance manual,very helpful as our local rotax expert was not available to do this rework for the next week.
The wiring diagram for the 6 pin module/4pin pickup is the one I need.
I intend to get back to the hanger later this week to finish,check and ground run.
My triggers are the type with a guide collar and no significant adjustment, but I will still check the gap.

[Dusty]

Update
I moved the modules (a pair of borrowed and good ones)to the cabin .
The coils are in their original location,so an extension lead was made to connect these to the modules.Right from startup was a definite improvement.
6 hrs flying apart from a couple of minor stumbles on takeoff all good.
I still don't know the source of the original problems but definitely a broken pickup wire. I had paired earths on the coils maybe another problem?
The next step after some minor tweaking and checking is to fit my original modules one at a time to see if these are good.:)

[Dusty]

Another 5 hrs and all good,the brief stumbles were still there which we are putting down to carb ice (autumn here mild temps high humidity)this may have been aggravating the broken wire misfire,but this has been sorted now, I will start a separate thread to cover the fix for this.

[DesertFox4]

Dusty, do you have the newest fuel pump on your 912 yet? When the old style acts up it behaves like you have described or drops out completely.

Here is a pic of the new style except this has the very expensive fitted hoses.
The new pump with just barbed hose fittings is about $100.00 from L.E.A.F.

10896

[Dusty]

Yup
That's the pump I have,rock steady 4.5 ibs pressure,even tried a piersberg? Have tried an electric boost and even a regulator.The fuel filters and lines have been changed and flows checked.
Hopefully we have eliminated fuel as a suspect.

[Dusty]

Update
Problem found! My 912 was running better apart from a few stumbles on takeoff.
Witnesses on the ground were at odds as to whether it was a lean miss or flooding but definatly not developing power on two cylinders.
The floats and float levels had been replaced and checked multiple times,so I decided to replace the float needles (again) the fuel hoses and banjo fittings were removed and everything blown with compressed air.
On testing fuel ran out the r/h carb filter,the carb was stripped again,blown out and visually checked ,nothing visable.
A bit of wire was wiggled in the fuel intake side of the needle assembly and blown again.
An object was observed flying out the port! whatever it was, it wasnt getting blown out untill it got broken up.
Reasembled and test flown, consistant idle,smoother running no more stumbles!
I now have had around ten hours of trouble free flying.
I was dealing with at least two seperate issues which have been resolved and can now really start to enjoy relaxing flight
The moral of the story,NEVER ASSUME .
The carb had been stripped blown out multiple times with the debris still in place,perhaps a magnifying glass should have been used,or as been suggested, pressurise the fuel system and the fuel flow flow visually checked from the needle seat, an obstruction may shown up as an irregular flow pattern.
I hope this lesson may someday save someone else a lot of grief.

[DesertFox4]

Glad you persisted to discover the cause and the remedy.
I had a similar issue after both carbs were cleaned and rebuilt. I couldn't even sync them the right one was so bad.
Removed it, disassembled it and found a small piece in of debris lodged in one of the tiny journals. Reassembled, synced and it has run flawlessly for two years since.

[Dusty]

The story continues
My 912 was now running perfectly;) I had the plugs on my early modules changed to 6-4-1 ?
I was flying on borrowed modules which needed to be returned.
My original module A was fitted and around 15 hours all good.
The fun started when I replaced module B,mag drop was 50-100 rpm more than on A.
Test flight saw possible roughness on full power and when on cruise a random kick in the airframe ( literally like someone kicking the airframe).
The borrowed B module was refitted,all good again.
Question 1,do modules fail like this?(starting on this module alone was good and the wires appear good)
Question 2, I have been told there is aftermarket modules available that are around half the price of the originals that also have a live feed for starting and in case of a stater failure.Can anyone confirm this and were do I get them?

[HighWing]

Not sure this will be helpful, but years ago I rebuilt my carburetors and the engine started running rough especially at idle. This was especially noticable after a flight while idling at taxi with fuel spilling from the carburetors. I can't remember where the suggestion came from, but I switched back to the original float needles and smooth. I learned that Rotax makes several versions of the float needles to accommodate the different engines. The difference being different hardness in the rubber tip of the needle. Apparently the one supplied with the rebuild kit was the wrong one for my engine and it allowed fuel to leak during the normal engine vibration resulting in flooding.

[Av8r3400]

The proper tips for our planes are the red (soft) ones.

[Dusty]

I originally had the orange tip needles, our local rotax supplier only has the black tips,I use clear vent lines that usually stain with overflow there doesn't seem to be a problem The engine was running perfectly until I swapped to my original module. With the borrowed module back on all is good again
I am sure it is a randome module fault so would be happier with two new ones.

[Av8r3400]

Dusty,

I wish you good luck in the replacement of the modules. I hope it works as well as it did for me.

You mentioned earlier if there was an "aftermarket" option for these modules. I did extensive searching for this unicorn also and came up with nothing. Further thought on the matter lead me to feel that the money for the modules, even as expensive as they are, is cheap insurance for the overall safety of the operation of the plane. When all was said and done, I still feel it was money well spent.

I would ask you to consider looking back at post #12 (http://www.teamkitfox.com/Forums/showpost.php?p=56289&postcount=17), telling why, when I did the conversion, I went to the latest model module, the 6x6. The newer module is more readily available and far less expensive.

[Dusty]

I agree that changing modules is cheap insurance,they are cheap compared to a damaged aircraft or a helicopter recovery,everything has a finite life,my modules are 20+years and 1200hours old,these things get a bad rap but have done ok!
I wonder if the rumer mill has confused the "unicorn"replacement modules with one of the aftermarket ignition systems available that have a similar function?

[Paul Z]

I have a set of 6X6 used modules for sale. I replaced them after my recent fiasco with Kickback eating my spray clutch. It turned out I had a Carburator problem on the pilot sided. I had both Carbs rebuilt & replace the Sprag clutch. When I pulled the engine I opted to go to the Soft Start Modules even though they were functioning properly, because I did not want to go through the pain of replacing the Sprag clutch again. If you are interested I would willing to sell them to you at a very reasonable price.

[WWhunter]

Paul,
If he doesn't want them, I may be interested.
Keith

[Dusty]

Hi Paul
Pm sent

[Dusty]

Email sent!

[fastfred]

How often should plug wires be replaced?

How long do the modals last normally ? Mine just started to drop 200 rpm on the left and it triggers the error on my new tach.