Problem with Secondary ignition…
Posted: Thu Feb 15, 2024 6:34 pm
by sonex1020x
Hi all ! George in Utah here flying legacy Sonex 1020 and Aerovee #356 normally aspirated. At runup the other day, noticed a larger RPM drop and rough running on the secondary igniton. Figured a fouled plug, so made an uneventful takeoff and flew for 45 minutes. Did not do an airborne mag check. After landing, decided another runup was in order and when switched to secondary, Very rough and could barely keep running. EGT on cyl #2 was falling off the scale on the secondary, obviously not firing. I’m not very savvy about electronics, so I’ll tell you what I did to diagnose the problem as best I can.
- Looked for anything obvious, wiring , loose connections, etc. and found all looked as normal.
- Replaced #2 sparkplug with a new one. The “old” one ( 5 hrs time) looked fine but sooty.
- Pulled ALL the ignition wires and checked resistance : #1 -10K ohm at 24" , #2 - 13K ohm at 32" , #3- 13K ohm at 30 " , #4 - 14K ohm at 27". These values seem okay ? Didn’t seem these values would explain #2 cylinder not firing.
- Trigger cap magnet still magnetized? Yes.
- Resistance check of both coils ( the co-pilot side one dedicated to #4 and #2, the pilot’s side is #3 and #1)
1 - Primary, terminal to terminal at 3.3 ohm on both coils.
2 - Secondary, a meter’s probe in each ignition wire hole = 13.4 K ohm on co-pilot side ( cyls. #4 and #2), and no reading at all on the pilot’s
side coil(cyls #3 and #1). This was the OPPOSITE of what I was expecting (assuming 13.4Kohm is good and 0k ohm is bad). I was
expecting a bad #2,#4 coil ! - Turned on Master and secondary switch and checked for 12v at top terminals. Yes, and coils warmed up quickly.
- Decided to measure resistance at ignition wire holes again just for grins. No change on co-pilot side, still 13.4K ohms, but now on pilots side
read 27.3K ohms! VERY confused now ! Another check after about 5 minutes or so and still 13.4K ohm on co-pilot side, but now back to
ZERO on pilots side. What am I missing here?
I am not sure how to check the triggers, so didn’t go on any further. It seems I DO have a bad coil ( chime in here if you agree or not), but it is not the one that would explain cyl #2 not firing. And, does only one half of a coil go bad ? I’m at a loss and could use your help in diagnosing the problem. Can I afford to just buy new coils, triggers, wires and trigger cap? Sure, but would rather not. I hate to think of these parts as just consumables needing to be replaced every so often. BTW, my Aerove has over 320 relatively trouble free hours on it.
Thanks for your help in advance. George.
Re: Problem with Secondary ignition…
Posted: Thu Feb 15, 2024 7:02 pm
by Bryan Cotton
The secondary should have less turns, and probably less resistance. So the 0 ohm may be ok. I’ve not measured mine.
How are your coils grounded? Just through the firewall mount or do you have a dedicated ground? If through the firewall maybe that ground connection has degraded with age. You could run a dedicated ground to the coil mounts and see.
Screenshot_20240215-170124-056.png (618.21 KiB) Viewed 4655 times
You can see my dedicated ground wires.
Re: Problem with Secondary ignition…
Posted: Thu Feb 15, 2024 7:05 pm
by Bryan Cotton
If just the #2 temp falls off I’d suspect a coil as opposed to a trigger. You could swap coils to see if it follows the coil. Or swap the #4 and #2 plug wires at the coil.
Re: Problem with Secondary ignition…
Posted: Thu Feb 15, 2024 8:00 pm
by WesRagle
Hey Guys/Bryan,
Bryan Cotton wrote:The secondary should have less turns, and probably less resistance.
That’s backwards isn’t it? Isn’t the “coil” is a step up xformer with many more turns on the Secondary?
I’ll be at the hangar tomorrow and will measure my 3 Ohm Dyna Coil if this hasn’t been resolved.
Wes
Re: Problem with Secondary ignition…
Posted: Thu Feb 15, 2024 11:21 pm
by Bryan Cotton
WesRagle wrote:Hey Guys/Bryan,
That’s backwards isn’t it? Isn’t the “coil” is a step up xformer with many more turns on the Secondary?
I’ll be at the hangar tomorrow and will measure my 3 Ohm Dyna Coil if this hasn’t been resolved.
Wes
Whoops you are right, I goofed.
Re: Problem with Secondary ignition…
Posted: Fri Feb 16, 2024 1:10 am
by daleandee
sonex1020x wrote:At runup the other day, noticed a larger RPM drop and rough running on the secondary igniton. Figured a fouled plug, so made an uneventful takeoff and flew for 45 minutes.
It was hard for me to read past this line. Not trying to be difficult but this seems to me to not be a great idea.
Certainly you are the PIC and I respect that, but flying a plane with a known ignition issue is not something I recommend …
Best,
Dale
3.0 Corvair/Tailwheel
Re: Problem with Secondary ignition…
Posted: Fri Feb 16, 2024 5:04 am
by Murray Parr
sonex1020x wrote:3) Pulled ALL the ignition wires and checked resistance : #1 -10K ohm at 24" , #2 - 13K ohm at 32" , #3- 13K ohm at 30 " , #4 - 14K ohm at 27". These values seem okay ? Didn’t seem these values would explain #2 cylinder not firing.
George.
If my memory serves me correctly from my old school mechanic days you should expect 4000 to 8000 OHMS per foot of ignition lead.
Re: Problem with Secondary ignition…
Posted: Fri Feb 16, 2024 10:28 am
by sonex1020x
Thanks Dale, but looking for helpful information, not lectures. George.
Re: Problem with Secondary ignition…
Posted: Fri Feb 16, 2024 2:04 pm
by daleandee
sonex1020x wrote:Thanks Dale, but looking for helpful information, not lectures. George.
George,
You are PIC and have the right to fly a broken airplane. It wasn’t meant to be a lecture but a warning that others will hopefully adhere to.
If you want my personal helpful information … install a Corvair conversion! 8~)
Dale
3.0 Corvair/TailWwheel
Re: Problem with Secondary ignition…
Posted: Fri Feb 16, 2024 4:03 pm
by WesRagle
Hi Guys/George,
I measured the resistance of a known good 3 Ohm DynaCoil. The primary measured 3.0 Ohms and the secondary as measured tower to tower measured 12.6 KOhms. Measuring from a tower to the core laminates measured OPEN.
EDIT: I contacted tech support at Dyantek and they said that the above measurements are the suggested trouble shooting procedure for their coils. The 3 Ohm and 12.6 KOhms are as expected.
Wes
Re: Problem with Secondary ignition…
Posted: Sat Feb 17, 2024 12:28 pm
by sonex1020x
Dale,
I resent your implication that i might be a careless pilot willing to fly a" broken airplane". You know NOTHING of my airplane, my experience or flight conditions that day. You should know that all takeoffs are optional, and carry varying risk that you can choose to accept or not. In my 56 years of flying, I have rejected or aborted my share of takeoffs for different reasons. I have never had an incident, accident, or even scratched an aircraft (outside of the hangar ,anyway 
) in those years. You may elect to not takeoff with a certain crosswind component, where i might feel it is safe. This does not make me an inherently reckless pilot. I posted many questions that i had regarding my ignition problem, none of which were “do you think I should takeoff with those conditions?”. Unsolicited and derogative advice is never appreciated. Secondly, you mock all of us Aerovee owners with your “Install a Corvair” ! If you want to continue to espouse your amazing conservative safety values and ideas, there are other places on this forum in which to do that. George.
Re: Problem with Secondary ignition…
Posted: Sat Feb 17, 2024 12:36 pm
by sonex1020x
To all you others who shared valuable information, Thank you ! FYI I ordered two new coils and a set of plug wires today, so hopefully that resolves my issue. And, did you know that Sonex considers a “set” of plug wires to be only two? No information on their Web Store to indicate a “set” is only two wires, not 4. If you go to any auto parts store to get a set of plug wires say, for a Chevy V-8, you will get 8 wires ! Go figure ! Thanks again, and I will re-post with results hopefully soon. George.
Re: Problem with Secondary ignition…
Posted: Sat Feb 17, 2024 12:43 pm
by daleandee
sonex1020x wrote:Dale,
I resent your implication that i might be a careless pilot willing to fly a" broken airplane". You know NOTHING of my airplane, my experience or flight conditions that day. You should know that all takeoffs are optional, and carry varying risk that you can choose to accept or not. In my 56 years of flying, I have rejected or aborted my share of takeoffs for different reasons. I have never had an incident, accident, or even scratched an aircraft (outside of the hangar ,anyway) in those years. You may elect to not takeoff with a certain crosswind component, where i might feel it is safe. This does not make me an inherently reckless pilot. I posted many questions that i had regarding my ignition problem, none of which were “do you think I should takeoff with those conditions?”. Unsolicited and derogative advice is never appreciated. Secondly, you mock all of us Aerovee owners with your “Install a Corvair” ! If you want to continue to espouse your amazing conservative safety values and ideas, there are other places on this forum in which to do that. George.
George,
I certainly didn’t mean to strike a nerve with you. But differing degrees of crosswind experience and willingly flying a plane with a known ignition issue do not comport.
BTW … my “install a Corvair” remark was totally in jest as should be noted by the smiley face …
Best,
Dale
3.0 Corvair/Tailwheel
Re: Problem with Secondary ignition…
Posted: Sat Feb 17, 2024 2:29 pm
by tps8903
sonex1020x wrote:To all you others who shared valuable information, Thank you ! FYI I ordered two new coils and a set of plug wires today, so hopefully that resolves my issue. And, did you know that Sonex considers a “set” of plug wires to be only two? No information on their Web Store to indicate a “set” is only two wires, not 4. If you go to any auto parts store to get a set of plug wires say, for a Chevy V-8, you will get 8 wires ! Go figure ! Thanks again, and I will re-post with results hopefully soon. George.
Hi George.
Not sure if it was mentioned already. A resistance test on coils isn’t always accurate. I tested coils that appeared fine but after replacement it was obvious that one of them was bad.
I got bit by the spark plug wire ordering issue as well.
Re: Problem with Secondary ignition…
Posted: Sat Feb 17, 2024 5:43 pm
by sonex1020x
Thanks Chris. I tried reasoning with Sonex and simply said they should note on their web store that a “set” of wires is only two. They said it is how their supplier sells them to Sonex. I replied, I’m not buying from your supplier, I’m buying from you. George.
Re: Problem with Secondary ignition…
Posted: Sun Feb 25, 2024 6:51 pm
by sonex1020x
Hi all ! George with an update. I purchased two new coils and new secondary ignition wires in hopes of solving the #2 cylinder not firing on the secondary ignition. No joy. Problem still exists. Barely will run on secondary only, and the #2 egt starts falling off. It runs just fine on the Primary ignition with all 4 egts reading as they should. Do you know if a bad trigger can result in just one cylinder not firing? And, what’s the best way to test the triggers? And, it looks like they can be replaced with the engine still mounted, but may have to take off the starter? Any ideas? I did email Sonex and will see what they say. I hate just replacing parts until the problem is solved, but may have to do that. I did check the magnet on the trigger cap and it seems strong. I looked on the Sonex web store and it appears they sell the set of two,prewired triggers that need to be mounted on the plate that is attached with six allen screws. Anybody done this replacement? Thx, George.
Re: Problem with Secondary ignition…
Posted: Sun Feb 25, 2024 8:00 pm
by Area 51%
One trigger fires one coil. One coil fires two cylinders.
If the second cylinder on any particular coil is not misfiring, the trigger would not be the culprit.
My next move would be to swap plug wires from the “bad” cylinder to it’s counterpart on the coil in question.
If the problem doesn’t move, it’s something non-electrical. .
Re: Problem with Secondary ignition…
Posted: Mon Feb 26, 2024 10:26 am
by sonex1020x
Well, that makes sense to me as well, but, if it’s not electrical but mechanical, why does #2 cylinder fire normally on the Primary ignition. Next time i’m out I will swap the plug wire from the number 2 location on the right coil, with the #4 plug wire on the same coil and see what happens. But the coils are new, so not really sure what that tells me? Confused in Utah !! George.
Re: Problem with Secondary ignition…
Posted: Mon Feb 26, 2024 10:44 am
by Area 51%
By mechanical I mean a problem with a wire shorting or a plug.
If you use anti-seize on the plugs, it’s not uncommon to accidently get some on the plug or wire. Either can cause the spark to jump in an unintended location.
Many moons ago in auto shop, we used to remove a wire from the distributor of someone we disliked and draw a line from the terminal to the body of the distributor with a pencil. “Pencil lead”, being mostly carbon, gave the spark a handy little shortcut to ground and was maddening to diagnose.
Lessons learned.
Re: Problem with Secondary ignition…
Posted: Mon Feb 26, 2024 11:15 am
by BobDz
Area 51% wrote:
Many moons ago in auto shop, we used to remove a wire from the distributor of someone we disliked and draw a line from the terminal to the body of the distributor with a pencil. “Pencil lead”, being mostly carbon, gave the spark a handy little shortcut to ground and was maddening to diagnose.Lessons learned.
I did the same thing! Many many moons ago.
Re: Problem with Secondary ignition…
Posted: Mon Feb 26, 2024 1:42 pm
by sonex1020x
Ignition wires are new and routed correctly. All plugs new(less than 5 hrs time on them) and #2 lower plug replaced with brand new when problem arose. I guess next step is to undo my entire FWF wiring harness and individually inspect all wires pertaining to the secondary ignition. Still can’t for the life of me see how only one cylinder is affected. George.
Re: Problem with Secondary ignition…
Posted: Mon Feb 26, 2024 3:19 pm
by Bryan Cotton
Bryan Cotton wrote:How are your coils grounded? Just through the firewall mount or do you have a dedicated ground? If through the firewall maybe that ground connection has degraded with age. You could run a dedicated ground to the coil mounts and see.
Screenshot_20240215-170124-056.png
You can see my dedicated ground wires.
George what does your grounding look like?
Re: Problem with Secondary ignition…
Posted: Mon Feb 26, 2024 7:31 pm
by sonex1020x
Hi Bryan. Coils are grounded to firewall and to the neg. batt post. Triggers are grounded to a “forest of tabs” block with everything else. Still just perplexed as how only one cylinder can be affected.George.
Re: Problem with Secondary ignition…
Posted: Tue Feb 27, 2024 9:47 am
by Tnhelm
I had a problem with one cylinder not firing on one plug after startup. I thought it was a bad coil. However, before changing the coil, I began checking the other cylinders with a spark tester and discovered I had a second weak spark on another plug. Turns out that when assembling the plug wires I had misinterpreted the instructions and not properly installed the plug wire end clips, (failed to fold center lead back over the outer portion of the wire to make contact with the clip). Considering you have changed the wires already, this is not likely the case. In my case, the only reason the engine was running fine (over 40 hrs) was because the spark was jumping the gap in the wire socket to the wire as evidenced by black residue in the coil socket.
Tnhelm
OneX 0137
Re: Problem with Secondary ignition…
Posted: Tue Feb 27, 2024 1:55 pm
by sonex1020x
I will definitely check the new plug wires I assembled, but it seems odd it’s still the #2 cylinder not firing. Will also swap the wires on the right hand coil and see if now #4 EGT falls off. George.
Re: Problem with Secondary ignition…
Posted: Tue Feb 27, 2024 2:07 pm
by BobDz
George
This is out there, but a post on another forum madame think of it. In high school we used to take a pencil and put a mark down a spark plug wire, and then watch our fellow classmates pull out their hair trying to figure out why it was misfiring. Not saying you have a pencil line, but is there any exterior contamination that could be causing a short? Run the engine in the dark and see if there is any arcing.
Re: Problem with Secondary ignition…
Posted: Sat Mar 02, 2024 12:19 pm
by sonex1020x
Hi all. Update. After installing 2 new coils, new ignition wires, plugs, and verifying all that done correctly, no joy. She still runs just fine on the primary ignition, but very rough on just the secondary, with the #2 cylinder’s EGT falling off. All the other 3 EGT’s are normal. Sonex recommended testing the triggers by using a voltmeter, pos probe on the orange wire at the coil, neg probe on good ground. With trigger cap magnet aligned with the trigger, I should get batt voltage. rotated another 180 degrees, should get around 1.5 volts. This of course with the secondary ignition on. I tried this and got batt voltage no matter how the prop was positioned, clear through 360 degrees. Never saw a lower voltage reading. This was consistent with both trigger assemblies. I have no idea what the results of this test is telling me. Any ideas ? Clearly my coils,wire and plugs were fine and weren’t the culprit . I hate to spend another $242 for triggers if they are not bad. George.
Re: Problem with Secondary ignition…
Posted: Sat Mar 02, 2024 1:00 pm
by Bryan Cotton
Like you, I’m somewhat skeptical that a trigger can cause one half of a coil to fail. I would assume you gap per the aerovee manual to 0.032" for the primary ignition. It might be interesting to try a closer gap on the #2 plug and see what happens. Also have you checked compression? As pressure gets lower there is less resistance for a spark to jump, which is why some airplanes have pressurized mags if they are going to altitude. Maybe the #4 cylinder is weak and the current is all going in that direction from the coil, but with the smaller gap on the primary plugs this has not manifested itself there yet. That would be an easy experiment to try if you had some old plugs laying around, which I bet we all do!
Edit: one way to rule out triggers would be to swap them.
Re: Problem with Secondary ignition…
Posted: Sat Mar 02, 2024 5:40 pm
by WesRagle
Hi George,
I’ve heard rumors that the new Sonex secondary ignition module shuts down after some period of inactivity to keep from burning up coils. Does anybody know if that is true?
Anyway, let me try to explain the way the secondary worked back in the day on my AeroVee. It might at least provide some food for thought. Since I owned an AeroVee Sonex LLC has changed coils and obsoleted the old trigger module. Things might be a little different now. But here’s how mine worked.
While the secondary ignition switch is on, there is 12 volts on one side of the primary winding. The other side of the primary went to the ignition module. The ignition module side was basically GROUNDED while the trigger magnet was NOT aligned with the sensor in the trigger module. When the trigger magnet WAS aligned with the sensor in the trigger module the ignition module side was OPEN.
So, for most of the time the ignition module side of the coil was grounded and the coil was charging, then, when the magnet passed the (hall effect) sensor in the ignition module, the ignition side of the primary opened up. Much like a set of points opening up.
Here is a pic Chris Madsen posted a long time ago that illustrates whats going on. The pic shows the current passing through the primary of the coil. The current jumps to zero when the magnet passes the sensor. This causes a large induced voltage in the coil secondary winding and the plugs (should) fire.
Here is a pic of the voltage on the ignition module side of the coil primary when the ignition module opens the circuit.
If you compare the two pics, when the current in Chris’s pic goes to zero you can see the large voltage spike on the voltage pic. That spike starts the spark event. Then there is a flat spot on the voltage pic. That’s while current is actually “jumping” the plug gaps.
Next comes the ringing on the voltage pic. That when there is no longer enough voltage on the coil secondary to arc the plug so the current in the coil secondary suddenly stops. That sudden stoppage reflects back on the primary much like what happened on the secondary when the current in the primary suddenly stopped.
Anyway, what comes next, after the ringing, the ignition module side settles in at 12 V. At that point the circuit is still open and no current is flowing in the coil primary so all you see is the 12 V power on the other end of the primary winding. That continues until the magnet clears sensor. At the very end of the voltage trace you can see the magnet clear the sensor and the module side of the primary is again grounded and the process repeats.
For dual plug coils to fire both plugs at the same time there is only one secondary winding. So, the plugs are in series with the secondary winding. In theory the secondary winding is “sucking” current from one plug and “pushing” it to the other plug. Not always the case though. If the coil arcs internally or if there is enough inner-winding capacitance (or some such techno babble) there may be enough current/charge available to fire only one plug.
Enough of that. So what to do.
Assuming you have done whatever you deem appropriate to ensure that you can fiddle with the prop while the secondary ignition is on without the engine firing, I would start by seeing if you can fire the plugs by exercising the ignition module by hand. You can do that hooking a volt meter to the ignition module side of the coil primary and moving the prop so as to make the trigger magnet pass in front of the sensor. You should see 12 volts (after a healthy spike) while the magnet is passing the sensor and zero volts while the magnet is clear of the sensor. If that works, then you have a good idea that the ignition module and trigger magnet are OK. This assumes the new ignition module works the same as the old ignition module.
Wes
Re: Problem with Secondary ignition…
Posted: Sun Mar 03, 2024 9:54 pm
by sonex1020x
Hi Wes. That’s alot of information,most of which goes over my head… Just a re-cap of what I’ve tested and the results, before I just go ahead and order new triggers for $242 ! Removed all 4 bottom pugs, and grounded them, one at a time, to observe for spark. Secondary ignition on, rotated prop and saw spark on #1 and #3 cyls. No spark observed on #2 or #4 . Remember, both coils new. Tested triggers per Sonex by aligning trigger magnet with module and measuring voltage (again, secondary on ) at orange wire/coil junction. I got batt voltage. Rotated prop to 180 deg and looked for about 1.5 volts per Sonex. but still got batt voltage. I got the same reading no matter where the prop was positioned. Never saw a lower voltage. This was consistent with both trigger’s orange wires. Just looking to know if this test proves anything. Thx. George.