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Interesting P-mag issue...

steve91t

Well Known Member
This one is a thinker...I'll try to keep it short while giving as much information as possible.

So a few months ago the weather was perfect for flying my dad's RV 7 to and from work. I was flying it every few days. It's an RV7 with an IO360 with P-mags and about 400 hours TT (I think). Mags had never been overhauled until recently. More on that later.

So, to make this post a little less boring, I'll include some pictures. Here is the plane freshly washed in Roanoke, VA minutes before heading home.



Flying home...beautiful flight.



It's running pretty **** good if you ask me. The true airspeed is a little lower than you might think, but that's because of the composite 3 bladed prop.



Now for the fun part. I park the plane at Lake Norman airport just north of Charlotte, NC for the night. The next morning I hop in and fire it up. I do my mag check and when I turn the left P-lead off, it bangs and pops in the worst way I've ever heard. Sounded terrible. EGT's went through the roof when I turned it off for any length of time. When I turned the right off, the RPM smoothed out and increased.

Fortunately there were some very nice mechanics on the field. After a full day of trouble shooting, they found that the right P lead was out of timing. They retimed it and all was well. I picked the plane up a few days later, flew it a short flight back to our home base and put it in the hanger. We sent the P mags out to be checked and they really didn't find anything wrong. Their suggestion was to have the left one rebuilt ($85) and the right one rebuilt along with a new circuit board just to rule out this happening again ($450).


We got them back and decided to install them today. We've never done this before but it seemed simple enough. We followed the instructions. Installed the mags, connected the proper plug wires, connected the plug. We set TDC by pulling a plug on #1, gently inserting a screwdriver to feel the piston movement, and rotating the prop till it stopped. We also found the TDC mark on the flywheel lined up with the seem in the case. We timed the mags by blowing into the tube. Got the green lights like we should.

We cranked up the engine and all seemed well, until we turned one mag off. 90 RPM drop on the left, 170 on the left with about a 150 degree increase in EGT. It also sounded bad with one mag off. We retimed the mags 3 times to make sure we had it right. No real change. The odd thing is that with both mags on, it sounds great. Smooth, no popping, nothing. It sounded like a perfectly happy engine.


So, to summarize....

Engine ran great
Overnight, right P-mag lost timing, but once timed, ran great again.
Mags rebuilt, nothing found wrong. Company has no idea what happened.
Now both mags have an unacceptable drop during mag check after rebuild.

We are confident that we set TDC correctly. But the tech guy even said if we were a couple of degrees off that we wouldn't even be able to notice it, implying that even if we missed it just barely, it would still be fine. But we didn't, we had the marks lined up.

We are at a loss. Why would they both have such a big drop? Before the rebuild, they would maybe lose 10-20 RPM. Almost no drop at all.

The tech guy insists that we have something else going on, like a fuel problem. I call BS on this because NOTHING changed. All we did was remove the mags and then reinstall the rebuilt ones. We didn't even remove plug wires. I am very confident that we have a timing issue, but I don't know why.

I'm sorry for such a long post. It's tough to keep it short and provide as much information as possible. If you guys have any insight as to what might be wrong, we are all ears. The good thing about this experience is that we are learning a lot about the airplane and how the systems work. The other good thing about getting stranded that one day in Lake Norman Airport is I got to see this...





Anyone redneckinize this old barn? Remember the barn scene in "Days of Thunder"? :) :) :)
 
What kind of plugs are you running? And it runs rough on the upper plugs or lower plugs?
 
NGK plugs, changed during the troubleshooting process (.5 hr flight on them). Right mag is lowers, left is uppers. Runs rough on one or the other, but when both mags on, seems fine. Of course we never got it higher than about 1400 RPM.
 
What about plug wires, if the mags work (should be just overhauled), plugs are brand new only logical problem would be maybe one of the wires is bad.
 
One bad wire would cause a big drop with both mags? No way.

How would a plug wire go bad on its own? You see the screen shot of the engine gauges the day before the mag lost its timing. There was nothing wrong.

It's got to be either something with the mags or something with setting TDC.
 
Random ideas...

Well for some ideas I'd suggest you put an ohm meter on every plug wire. I believe they give you the resistance per foot in the manual, but they should be all pretty close to each other. You said you put in new plugs, also make sure they are solid tops, the screw on ones can missfire if they come loose, had that problem myself.
Second, test the manifold pressure plumbing. If one is getting vacuum and the other isn't that would account for some difference. You can put an automotive timing light on #1 cylinder and see where it is firing, then check the other system on the same cylinder....they should be the same. Check it again with the vacuum disconnected and plugged back to the engine.
Bottom line is this: with 8 good wires and plugs, both systems firing at the same time, it has to be elsewhere. We should be able to assume the engine is mechanically sound since it runs fine on both.
Another thought is you should be able to see a bad plug or wire from a EGT rise that's different from the others when you kill on side or the other.
Final suggestion is swap the PMAGs from side to side and see if your troubles move also.
 
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Ohm?

Have you ohm'ed the plug wires?
The allowed ohm pr foot is described in the P-mag manual.

Maybe one wire has gotten a loose connection in a booth during the P-mag swap? Or maybe a wire is broken?

It's easy to yank the wires alittle because of the tight space when off- or on mounting the P-mags.


Brad at E-mag is VERY helpful and they truly are standing behind their product, so I'm sure he'll help you in any way he can.
 
Thanks for the suggestions. But I don't think it's the wires. Think about it, how would all 8 wires all go bad at the same time. Like I said, both mags run like **** on their own. That's not a single plug wire issue.

I forgot to mention that the EGT rise while running on one mag was across the board.

As for the manifold plumbing, that's an easy one. They are T'd into the same source. All we did is unplug the line from the mags. We simply plugged them back in when installing.


I'm not trying to be difficult in any way, but think about it. Nothing changed other than the mags. We aren't dropping a cylinder on a mag check, that's easy to identify. That would be what happens with a bad wire.

It's acting like the timing is retarded when doing a mag check. BOTH mags respond the same way.

This is not a situation where we have a big drop with one only.

Thanks again guys.
Steve
 
A logical nest step would be to replace one P-mag at a time, just to see if the problem is with one or both P-mags.

Maybe one at your airport has a P-mag you can borrow?

Or maybe Brad can send you one to try out for a couple of days?
He's a great guy so it can't hurt to ask...?
 
did you make sure that none of the spark plug wires are swapped on one mag?
it may run on 2 cylinders only on one side, with the other 2 cylinders firing at the wrong stroke.
 
Pull Thru Test

The P-Mag manual walks you thru a pull thru test. Essentially remove all the plugs and connect them back up to the wires and ground them to the engine, bottom ones are tough, top ones you can lay on metal on top of the engine.

Pull the prop thru and see where how they fire and see if they fire in the same spot, both plugs in a cylinder should fire at the same time.

I had the same issue you did a couple months ago, mine turned out to be the circuit board it has been fine since replacing the board. My mags where a couple years old from when I bought them but only had 65 hours on them since I only started flying back in December.

When I experienced the bang during the mag check, I did the pull thru test and determined the bad mag was firing well late of the other mag. Sent the mags in for a look see and they could find nothing wrong with them. Brad gave me the option of getting a new circuit board that I could install if the mag did the same thing again. I installed the mag timed and went for a flight and all was good till the next flight then loud bang during mag check when trying to run on the bad mag. I put in the new circuit board and smooth running so far, 40 hour on the new circuit board. My thought was some connection on the board was loose and would allow for a good timing and then one flight then during flight something causes the timing to dump you don't notice it because the good mag is running well.

How often do you do the internal power test, I have wondered if that might make something go bad. Mine ran fine for 60+ hours and of course it goes bad with I am on the road. Yours is odd in that even with the new circuit board you are having issues. No heat issues with my set up, non of my sticker turned color.

Good Luck
Mike
 
You say the EGTs are going up together on one mag. That says to me that the operating mag is retatarded. Late firing and the fire is still burning well when the ex. valve opens.
Try timing them again from the start.
 
NO........

EGT rise on one mag is EXACTLY NORMAL.

In any mag check the EGTs should all rise together, not necessarily identically but roughly so.

The reason for his is a slower burn completion, later Theta PP, lower ICP and less expansion of the gases.

PV=NRT.
 
Not sure about the rough running on one Pmag but it is fairly common to see reports of large drops between two Pmags. Lots of reports of this on here. Not sure if anyone has ever figured out why.

When you say it runs rough, please elaborate.
 
I wouldn't completely ignore mixture. A really lean mixture is hard to ignite, rough running, leading to popping in the exhaust by the wasted spark. Both ignitions firing can overcome this. How does the airplane perform, and what are the climb EGTs at full rich? Do you have around 300 degrees between full rich and peak lean?

John Siebold
 
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Agree w/Oz...the EGTs should go up.

What curve are you on?

Do you have a orifice / filter in your manifold pressure line that T's into the PMags? I didn't initially...and it caused issues as the cylinder pressure pulses varied the PMags timing at higher power settings. You might try disconnecting the MP line and doing the run-up...this would eliminate the MP / timing curve variable.

Are you leaning out prior to accomplishing the run-up?

I'd start at the plugs (sounds like you've done this) and work backwards toward the PMags. After you test...what are the lights doing when you pull the prop toward TDC? Are they turning green almost in unison?
 
Check out Lycoming Service Instruction No. 1437 just to be sure everything is good there. I use the TDC mark on the front of the ring gear and actually retard the timing about one tooth to prevent kickback during starting. Also, make sure your plug wires have some separation between them. I've been running PMags for about 400 hours and I only get about a 50-70 rpm drop between them. Let us know what you figure out.
 
Thanks again guys.

Please make sure you read my responses as I've covered most of your questions.


Once again, absolutely NOTHING changed. We pulled the mags off and sent them in to be rebuilt and then reinstalled them. So if the plug wire routing and MP line were ok before, it should be fine now. We used to get only a 20 RPM drop on one mag. There is nothing wrong with wires or the MP line.

Also, we retimed it 3 times. Not only were we using the mark on the flywheel to line up with the case seam, we pulled a plug on #1, pulled it through until we felt compression, and then gently used a screwdriver to feel for the top of the travel. This was to make sure that the ring gear was installed properly.

We aren't dropping a cylinder or two during a mag check. As I've said, all 4 cylinders are firing and all 4 EGTs increase. Now, some of you say that's normal. I've never ran in on one mag for long enough to see that increase.


When I say ran rough, the exhaust note sounded off. The engine sounded labored. It actually got louder and honestly sounded as if the timing was off.


Now, what's his face over at P Mag told us to try setting the timing a couple of degrees retarded to prevent kick back. We did and it ran worse. When we set it at TDC, it ran better, but still getting that off sound and 175 rpm drop on either mag.

Is it possible that the rebuild didn't go well and they screwed something up? One mag, the right, has a brand new circuit board and that one has the largest drop of the two.

Honestly, I feel that we almost need to set the timing at a few degrees advanced to get these mags to fire properly. Alsmost like setting setting TDC causes them to retard while engine is running.


To answer another question, the MAP line comes from a box mounted on the firewall. I didn't take the time to see exactly what it is. Also, both green lights illuminated at the exact same time.

Doing the mag check rich, lean, 1400 RPM, or 1000 RPM produce the same result. It's a timing issue.
 
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Steve...

I've had the P-Mags decide to "re-time" themsevles once.

So firstly retime them (as you have done) - then once you get the "banging" syndrome, confirm they are still timed:
Power to P-Mags On , Ignition (P-Leads) off, rotate Prop until green light - ensure both green lights same time and at #1 TDC marks. This ensures the P-Mags are staying timed.

To confirm mixture / injectors, run engine up to ~1200, full rich, both P-Mags on. Write down 4 x EGT. Pull mixture back a bit, hopefully get RPM rise and write down 4 x EGT again. Repeat until runs roughly. You want to be able to pull mixture lever back quite a long way, and see ~even EGT rise across all 4.

There is no need to use the screwdriver in #1 - it does not matter (unlike a Mag) which rotation it is on.

I would also disconnect the MP lines to both P-Mags and see how you get on for the Mag checks. There will be no advance then, just like Mags. Adds another point of interest for the experts on here re engines.
 
His name is Brad

Steve;

There is a troubleshooting guide on the EMag web site. I'd suggest (so would Brad) that you go through every step rather than declare it a timing issue. It indeed may be a timing issue, but there is more information that you can gather.

There is data in ohming the wires and doing the pull through test. The data may be that they are not the issue, but for now you don't have that data.
 
Just an observation

Steve,
Just an observation here. (I have dual P-Mags so I am following this thread)

My observation is you have convinced yourself that you know what the problem is, but all your diagnosis tells you it is fine. You seem to be ignoring others recommendations (the ones you asked for) by validating "nothing has changed" and "it WAS working fine". Everything works fine, right up to the moment it breaks!

I am not trying to be sarcastic, but would suggest you take a moment and back away from the problem and read the suggestions. Then systematically step through them from plugs to PMags till you find the problem. I know it is frustrating, but your frustration is just going to blur the solution.

IMHO,

Dan
 
In flight mag check...

A couple of thoughts... a ground run mag check is a course measure to ensure that you don't have an obvious ignition issue. 1,400 or 1,000 RPM is low for a ground run... I do mine at 1,700-1,800

A better practical test of your ignition system is an extended inflight mag check. It is good to test and familiarize yourself with how the engine operates on a single mag and will provide more meaningful information.

Also, since you have one ignition firing the top and the other on the bottom you should expect some difference in performance between the two... Best evaluated if flight at cruise power. I have mine set traditionally with half top and half bottom for each PMag.
 
The suggestion of plug wires getting swapped on the Pmag seems the simplest response that would have this effect. Personally, whether I'm wrenching on motorcycles, race cars, weedeater or airplane my first assumption if a replaced part is running wrong is assembly error. While it has certainly happened where the part was faulty...the most common issue is I swapped something simple. Usually that occurs in the "cruise mode" stuff where I'm not thinking about it much and just putting stuff back on. Check that every plug wire is where you want it and double check the wiring connections are good in the screw down block. Then, run through the website troubleshooting step by step. If that doesn't work....punt (call Emag) and send them back or swap with known good ones.
 
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I did it.

The suggestion of plug wires getting swapped on the Pmag seems the simplest response that would have this effect. Personally, whether I'm wrenching on motorcycles, race cars, weedeater or airplane my first assumption if a replaced part is running wrong is assembly error. While it has certainly happened where the part was faulty...the most common issue is I swapped something simple. Usually that occurs in the "cruise mode" stuff where I'm not thinking about it much and just putting stuff back on. Check that every plug wire is where you want it and double check the wiring connections are good in the screw down block. Then, run through the website troubleshooting step by step. If that doesn't work....punt (call Emag) and send them back or swap with known good ones.

After I had my PMags checked, I installed two wires wrong and it acted a lot like this. Retarding the timing a couple of degrees should not even be noticeable. I think the wires are crossed or you are not timing it where you think you are. The marks on the front of the fly wheel are easier to use. I would cross reference them. Remember it should be on the TDC mark not the mag timing mark. BTW, is the mark on the back of the flywheel TDC or a mag timing mark? If there are both, make sure you are using the TDC one. You do not time PMags like traditional mags. Please let us know what you find.
 
Steve,
Just an observation here. (I have dual P-Mags so I am following this thread)

My observation is you have convinced yourself that you know what the problem is, but all your diagnosis tells you it is fine. You seem to be ignoring others recommendations (the ones you asked for) by validating "nothing has changed" and "it WAS working fine". Everything works fine, right up to the moment it breaks!

I am not trying to be sarcastic, but would suggest you take a moment and back away from the problem and read the suggestions. Then systematically step through them from plugs to PMags till you find the problem. I know it is frustrating, but your frustration is just going to blur the solution.

IMHO,

Dan

Right, but some common sense can tell us where to look. Also, something that I can't really describe very well is the way the engine was running. A crossed or bad plug wire is obvious. EGT, CHT, sound...that alone absolutely rules out a bad wire or plug, right? Sometimes sitting back and thinking is better than just testing stuff that we know is working.

A couple of thoughts... a ground run mag check is a course measure to ensure that you don't have an obvious ignition issue. 1,400 or 1,000 RPM is low for a ground run... I do mine at 1,700-1,800

A better practical test of your ignition system is an extended inflight mag check. It is good to test and familiarize yourself with how the engine operates on a single mag and will provide more meaningful information.

Also, since you have one ignition firing the top and the other on the bottom you should expect some difference in performance between the two... Best evaluated if flight at cruise power. I have mine set traditionally with half top and half bottom for each PMag.

I usually also do my check at higher RPM, but we've also done it lower and never got much of a change. I believe my dad did wind it up once while doing a check, above 1500 and there was no change. I agree we could find out a lot more if we flew it.....I ain't flying it until we figure out a little more. Plus, timing issues can destroy engines. Really no reason to fly it right now when we have the problem on the ground.

The suggestion of plug wires getting swapped on the Pmag seems the simplest response that would have this effect. Personally, whether I'm wrenching on motorcycles, race cars, weedeater or airplane my first assumption if a replaced part is running wrong is assembly error. While it has certainly happened where the part was faulty...the most common issue is I swapped something simple. Usually that occurs in the "cruise mode" stuff where I'm not thinking about it much and just putting stuff back on. Check that every plug wire is where you want it and double check the wiring connections are good in the screw down block. Then, run through the website troubleshooting step by step. If that doesn't work....punt (call Emag) and send them back or swap with known good ones.

I've done it as well...more often than I care to admit. But we spent about 4 hours installing these mags yesterday. We both checked everything several times before the initial start. Then many times after we realized something was wrong. If the plug wires were crossed, we would loose half the engine.

After I had my PMags checked, I installed two wires wrong and it acted a lot like this. Retarding the timing a couple of degrees should not even be noticeable. I think the wires are crossed or you are not timing it where you think you are. The marks on the front of the fly wheel are easier to use. I would cross reference them. Remember it should be on the TDC mark not the mag timing mark. BTW, is the mark on the back of the flywheel TDC or a mag timing mark? If there are both, make sure you are using the TDC one. You do not time PMags like traditional mags. Please let us know what you find.


So the reason I found true TDC on #1 was to verify the timing marks on the flywheel instead of just assuming they were correct. The TDC mark on the back of the flywheel lined of perfectly with the seam of the case along with a black sharpie mark over one of the holes of the starter. We also saw the mag timing mark and did not use that one.
 
My dad contacted E-mag and Eric agrees that we are indeed timing the mags correctly. As you guys suggested, Eric wants us to pull the prop through to make sure the green light illuminates at TDC. That and run the engine with the MP line disconnected and see how the effects the run up. If we are still having issues, he wants us to send them back to him and have him check the programing. He said sometimes battery chargers can cause problems if the mags are on while it's turned on. We did charge the battery, but didn't have the master or mags on while it was plugged in. But again, he said something could be wrong with the programs.

When the engine is run without the MP line hooked up, do we have to cap it off on the engine or mag side? Also, because it isn't advancing, it should run really bad, right? Spark too retarded? Possibly the MP line upstream of where I was blowing is housing a spider or something? Doing a mag check with this line disconnected will rule this out.

I know I'm shooting down a lot of your ideas, and I don't want to seem like I'm not appreciative. But if you guys heard this engine running, you would understand that it isn't a plug wire issue.

Let me ask you guys this, what indications would you get if we messed up the plug wires? On one mag, two cylinders would not fire, if not all 4. Right? That's why I'm telling you guys that it's something other than plug wires.

One thing that I've learned is when you change a part and then there's a problem, it's probably whatever you were messing with, not something else that magically failed during the work.

Now, my dad is going down there probably tomorrow to try some of the things we talked about.


Since these mags are so easy to pull off, after my add does the tests tomorrow, he'll pull the mags and send them back to have them checked. Now, if they come back and found no problems, and it still has an issue durning a mag check, we will have no choice but start from the plugs and work our way back.
 
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I just want to say again, thank you guys for all of your help. It's great to see so many people here to help. I hope I get to return the favor someday. I'll let you know what we find.
 
When the engine is run without the MP line hooked up, do we have to cap it off on the engine or mag side? Also, because it isn't advancing, it should run really bad, right? Spark too retarded? Possibly the MP line upstream of where I was blowing is housing a spider or something? Doing a mag check with this line disconnected will rule this out..

If you run it with the MP line disconnected (local atmospheric pressure), the Pmag will think it is at a high MP and therefore won't advance the timing at all. In this case it will run just like a regular Mag firing at about 20° BTDC. This alone will not cause the engine to run rough.

If you connect a laptop to the Pmags and use the EICAD software, you can use the tools available to help in your troubleshooting.

EICAD%20Display%20Guide%20i.jpg
 
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MP line

Just pull the MP line. I believe you said you have a 'T' from the MP cylinder line to the P-Mags. Just disconnect that line. The engine should not run rough at all. Disconnecting the MP line will prevent the P-Mags from advancing the timing, essentially turning them into regular mags firing at 25 deg BTDC.

As for the plug wires, I am sure you are convinced they are not they problem and you are probably correct, but to save you headache here and satisfy guys trying to help you. You could ohm check them, and verify they are connected correctly once more and post those results. ie "We ohm checked all 8 plug wires and ensured they were reinstalled properly.....problem still persists"

One question and this is a shot in the dark, did you change orientation of the P-Mags when you re-installed them? The orientation does not matter, but if lets say you rotated the P-Mag 180 degs and then reinstalled the plug wires according to the old orientation just by looking at the back of the P-Mag vice its original orientation, you could have the wires appearing they are on correct, but in fact are on opposite cylinders.
 
Just pull the MP line. I believe you said you have a 'T' from the MP cylinder line to the P-Mags. Just disconnect that line. The engine should not run rough at all. Disconnecting the MP line will prevent the P-Mags from advancing the timing, essentially turning them into regular mags firing at 25 deg BTDC.

As for the plug wires, I am sure you are convinced they are not they problem and you are probably correct, but to save you headache here and satisfy guys trying to help you. You could ohm check them, and verify they are connected correctly once more and post those results. ie "We ohm checked all 8 plug wires and ensured they were reinstalled properly.....problem still persists"

One question and this is a shot in the dark, did you change orientation of the P-Mags when you re-installed them? The orientation does not matter, but if lets say you rotated the P-Mag 180 degs and then reinstalled the plug wires according to the old orientation just by looking at the back of the P-Mag vice its original orientation, you could have the wires appearing they are on correct, but in fact are on opposite cylinders.

We traced the wires from the plug back to the mag to make sure that wire went to the proper spot (either top of bottom of the mag, per the instructions).
 
Like you Steve, we bought second hand P-Mags when we were building and they were wired up right mag fired the top plugs and the left the bottom (I think that's how they were). First engine start and mag check showed the left mag dropped 10-20 rpm more than the right mag. Ok, thought this was just different flame travel between the top and bottom plugs, but being a bit suspicious with second hand as to why the original owner sold them, I decided to purchase a new mag and a compete set of new leads from Brad at Emagair. Being in Australia I thought it was a good idea to have a spare anyway.
I never fitted the mag or leads as apart from the 10-20 rpm more mag drop they were performing perfectly for two years, then a mag check showed no rpm drop on the right mag and 70 rpm drop on the left (normally it was 20 rpm drop on the right and 30-40 on the left).
Ok, time to fit the new mag, timed it and fitted the new leads to the new mag only. Started up and did a mag check, Holly ****!!! It ran sick as **** on the left mag!!! Pulled the new leads and refitted the old ones. The old leads were tied up as a loom and slipped straight on the mag with out having to work out where they fitted.
Another mag check and it was back to it's old self of 10-20 rpm more drop on the left mag. It ran nice for about ten hours, then it started dropping more rpm on the left mag. Pulled the leads and ohm checked them, two leads were way out (****, why didn't I check them before???). Ohm tested the new leads, perfect!!
Not being able to get the head in behind the motor to read the lead numbering on the mag the first time I fitted them, I used a mirror to read them. Thinking I may have somehow got it wrong by a "mirror image" affect the first time I fitted them, So this time I used the the old mag to locate the leads on the new one (why didn't I think of that before. I also I replaced all the leads on both mags and wired them up two to the top and two to the bottom. She now runs perfectly and has for 30 odd hours with both mags dropping 30 rpm each.

Bob
 
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Wire connectors

Steve,

Check the power and signal wires and connectors very well. I had a similar issues and was completely flummoxed until I checked wires, snugged the screws and cleaned and reseated the connectors.

I put in new plugs, made new wires....nothing worked until we took a look at the connector. I don't understand why, but it was the issue.

Same as you, the engine sounded "wrong" (technical term).

No idea if this is worth anything - but wanted to throw it out there.
 
Steve,

Check the power and signal wires and connectors very well. I had a similar issues and was completely flummoxed until I checked wires, snugged the screws and cleaned and reseated the connectors.

I put in new plugs, made new wires....nothing worked until we took a look at the connector. I don't understand why, but it was the issue.

Same as you, the engine sounded "wrong" (technical term).

No idea if this is worth anything - but wanted to throw it out there.

Thank you, we will definitely check the connections.
 
Connectors...

I will echo what Pete said... I had a bad mag check and found that my right pmag was way out of time. On inspection the power wire in the screw down 'computer type' plug was no longer firmly attached and the hold down screw had backed off. I reattached, and retightened all of the connectors, retimed the pmag and all was good again.
 
I will echo what Pete said... I had a bad mag check and found that my right pmag was way out of time. On inspection the power wire in the screw down 'computer type' plug was no longer firmly attached and the hold down screw had backed off. I reattached, and retightened all of the connectors, retimed the pmag and all was good again.

This connection is the main reason I won't consider pmags till it is improved.

If I recall right, a "way out of time" mag can damage the motor.... Am I wrong here?
 
While not common on aircraft, that type of connector is very common in the industrial automation world. I have seen literally thousands of them in my career on all kinds of machines and equipment. Both in non moving static as well as high vibration applications.

I would not judge the Pmag based on that connector alone. Yes they can have bad connections but show me an affordable connector that never fails or that never needs maintenance....

When I first put in my Pmag, I kept a close eye on this connector every time I had the cowl off I would check the tightness of the wire hold-down screws and the connector hold down screws. Never found one loose so I now only do it occasionally.

If I were EMagAir, I would put an inexpensive 9 pin Dshell connector on there and lose the stigma associated with those phoenix connectors even if they are not a real problem.
 
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So there are two small flat head screws that hold the connector to the mag, but there is another connection? There are wire hold down screws?
 
Wire retention screws on top...

I am referring to the six wire retention screws that clamp down on the individual wires, not the two screws that safety the connector block to the housing... On top of the connector in the image.
 
adel clamp

Right, but that's it, right?

There is a small adel clamp that anchors the wires to take the stress off of the connector. It is attached with one of the coil pack retention screws. Also, I don't know if it is good or bad but I used ferrules on the wires going into the connector. I haven't had any problems. Remember, my advice is worth what you paid for it.
 
Yep, I crimped on some small diameter brass tube (ferrule) as well. Did not like the suggestions to solder or simply smash the wire ends under the terminal screws.
 
The wires were clamped to one of the bolts to the mag to take the tension/vibrations off the connector. But what's a ferrule?
 
I forget how the builder of Steve's plane wired his P-mag ignition switch (I lived in Huntersville at the time Randy built it.) but cannot recall if he put in dual toggle switches or not. (I think he did.)

Prior to firmware version 40, there was a bug that would allow the P-mags to reset the timing, if the plane was started on one P-mag while the other was powered up but grounded.

With toggle switches, this can happen fairly easily. Version 40 fixed this and moved the timing for starting to four degrees past TDC rather than at TDC.
 
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