Emi troubleshooting.

[Will.iam]

I have isolated the static noise on both my radios to the left Magneto i have a surefly on the right and when i run on only the surefly the noise is gone from both radios. ATC says my transmissions are clear on both radios so this is only effecting receiving. Last oil change i swapped all sparkplugs that were on the surefly with the ones on the magneto and the noise is still only with the magneto side. Is there a way short of taking the magneto for an IRAN to see what is causing the noise? This noise has appeared in the last 2 months. I had my magneto IRAN in oct 2021 on my first annual as it was at it’s 500 hour point. It performed flawlessly in the 11 months i had the plane before i IRAN it only because it was at its time for a check. Now less than 230 hours on it and it seems to be the source unless there is something else i can test or check as i do not want to do another IRAN this early and it would be even a bigger bummer if the IRAN did not fix it. I installed new maggie harnesses on both the mag and the surefly in that first annual so i would not think it would be the electrical components but yet with a mag check in flight the noise stopped so it’s definitely one of the three or something else I’m overlooking that maybe the mooney hive might know to check?

[Fly Boomer]

33 minutes ago, Will.iam said:

Now less than 230 hours on it and it seems to be the source

Who did the IRAN?

[EricJ]

If you're doing testing on the ground, try disconnecting the left mag p-lead at the mag and see if that clears it up.   The usual caveats to be careful around the prop while it is disconnected since the mag will be hot.   Or just triple check all the shield grounds on the p-lead at the mag, firewall, and switch.    You're checking to make sure the p-lead isn't a transmit antenna for mag noise when it is running.

Otherwise, if there's a tach sensor or anything else connected to the mag, check those as well.

 

[PT20J]

You could check the p-lead shield. If it is only grounded at the mag and was not reconnected when the mag was reinstalled then it may be floating when it should be grounded. 

[MikeOH]

This really sounds like a shield issue.  I think the money bet (what I'd check first) is the P-lead shield ground just like PT20J suggested.  Check for fraying and if the method of connection to ground is solid (e.g. a crimp ring terminal).  Sounds like it worked for awhile after the IRAN so it seems to me something has 'come loose.'

[Ragsf15e]

Differential diagnosis (after doing the p lead stuff above) is to swap out the left side harness.  It could definitely be the harness…

[Will.iam]

Interesting things to try about the shielding of the p-lead will check that first. And that triggered a maintenance action that was done on this last annual in that i have a digital tach and ever since the surefly was installed the tach  could not read the rpm’s from the surefly. I. E. I would have the tach working on both and when i did a mag check it would verify the drop in rpm’s on the mag but would zero on the surefly. Dugosh said it needed a special resistor wire from horizon to read the surefly and he didn’t have it at the time. So this last annual i got the resistor wire and the tach can now read the surefly too so i wonder if that was installed without a shield and the emi noise is coming from that wire? But I’m not getting emi when the surefly is the side that is running, only when the mag side is running. Could the mag noise somehow be traveling over and down the surefly resistor wire to the tach? It would match about when i started getting noise in the radios. When i get back from this trip i will look at the p-lead shield for any obvious loose or disconnected shielding. 

[Will.iam]

I would like to thank everyone for their comments for solutions to this problem. I found the problem but it was not what i was expecting and realizing the situation made me sick to my stomach what could have happened. This is a public safety announcement to anybody that has maggie sparkplug wiring harness. There are 3 screws that secure the cap of the wirings to the base of the magneto or surefly if you have one installed. The cap on my magneto side had all three screws vibrate loose and fall out in the course of 2 years. I guess the final screw let go just a few months ago and the cap being the leads have springs at the end, pushed apart thus allowing all the EMI noise to come out. I was shocked that the mag was still able to still get a spark across all six leads with the cap only siting loosely on the mag. The only reason the cap did not fall off completely is the fact that the sparkplug wires where pressing against the firewall keeping the cap in place, a testament to the tight quarters in the engine compartment. I installed 3 new screws and did a test flight today and surprise surprise the noise is reduced back to what i remembered as normal. In fact ironically the mag side is now just a little quieter than the surefly side. Looking at my p-leads they look like they are unshielded? I. E. Just the wire no wire mesh around it. Should i get that added? Not sure if that will help further or not. On further magnification i think the p-lead is shielded on the mag side as that looks like braided lining, but the surefly side looks different in just a white insulation type wire they definitely do not look the same?

first pic is the way i found the cap on the mag  second picture is of the p-lead to the mag as i was still searching for screws to fit the cap  third pic is of the p-lead to the surefly note the different color style of insulation between the two p-leads.

[EricJ]

Those may still be shielded p-leads, as many people use shielded wires with a tefzel jacket, i.e., there's still white tefzel on the outside, then the shield, then insulator, then the center conductor.     You could trace both ends, particularly to the firewall, and see if the shield is grounded on one (or both) end.

[HoJo87]

On 7/28/2024 at 1:11 PM, Will.iam said:

I would like to thank everyone for their comments for solutions to this problem. I found the problem but it was not what i was expecting and realizing the situation made me sick to my stomach what could have happened. This is a public safety announcement to anybody that has maggie sparkplug wiring harness. There are 3 screws that secure the cap of the wirings to the base of the magneto or surefly if you have one installed. The cap on my magneto side had all three screws vibrate loose and fall out in the course of 2 years. I guess the final screw let go just a few months ago and the cap being the leads have springs at the end, pushed apart thus allowing all the EMI noise to come out. I was shocked that the mag was still able to still get a spark across all six leads with the cap only siting loosely on the mag. The only reason the cap did not fall off completely is the fact that the sparkplug wires where pressing against the firewall keeping the cap in place, a testament to the tight quarters in the engine compartment. I installed 3 new screws and did a test flight today and surprise surprise the noise is reduced back to what i remembered as normal. In fact ironically the mag side is now just a little quieter than the surefly side. Looking at my p-leads they look like they are unshielded? I. E. Just the wire no wire mesh around it. Should i get that added? Not sure if that will help further or not. On further magnification i think the p-lead is shielded on the mag side as that looks like braided lining, but the surefly side looks different in just a white insulation type wire they definitely do not look the same?

first pic is the way i found the cap on the mag  second picture is of the p-lead to the mag as i was still searching for screws to fit the cap  third pic is of the p-lead to the surefly note the different color style of insulation between the two p-leads.

 

Hello William! Christine from Maggie Ignition Systems here! 

 

We pride ourselves on customer satisfaction and safety and would like to further discuss with issue with you ASAP in depth. Please call me at 310-648-1593 so that I and the shop foreman can discuss with you.

[Will.iam]

1 hour ago, HoJo87 said:

 

Hello William! Christine from Maggie Ignition Systems here! 

 

We pride ourselves on customer satisfaction and safety and would like to further discuss with issue with you ASAP in depth. Please call me at 310-648-1593 so that I and the shop foreman can discuss with you.

I talked to christine at maggie and to be clear the screws are installed by your A&P not at maggie which makes since as they do not know if the harness is going on a surefly or magneto. This is the first case they have heard of screws coming loose on the cap. Maybe my engine is producing more vibration than normal or the screws on the magneto were not tighten properly as my screws on the surefly are still tight. I still think maggie harness is a great product and it has worked flawlessly including when this cap came loose from the magneto the magneto still was working and if it was not for the increase noise in the radio i would not even known there was a problem. 

[A64Pilot]

When you replace the screws, I’m a fan of blue Loctite here, do not use red.