Joe Larussa Posted January 27, 2022 Report Posted January 27, 2022 Went to do a run up before departing yesterday. Right mag 60 drop, left mag running rough. Noticed while taxing out cylinder 4 30 degrees colder than the rest. Taxi to mechanic to figure this out. We check plugs on number four, no visible issues. Do continuity test and bottom plug fails. We clean top plug and replace bottom plug with new. No change. Decide to pull all plugs. Mechanic notices wire end to bottom number two is cold. Cleaned all plugs and reinstall and a little better. We swap bottom plugs to top and now back to normal. Flew for a few hours and all back to normal. I don’t understand. thoughts? 1 Quote
ArtVandelay Posted January 27, 2022 Report Posted January 27, 2022 How old is the ignition harness? They do deteriorate, with automobiles it usually shows up first when weather is wet, high humidity. 1 Quote
Yetti Posted January 27, 2022 Report Posted January 27, 2022 Check ignition leads with ignition lead checker. I thought that was mine, but just a fouled plug. Which was caused by no leaning and lots of ground running. Grumpy IA said "fly the plane more" Quote
carusoam Posted January 27, 2022 Report Posted January 27, 2022 Check name on spark plugs… if they say Champion…. Measure their resistance… Old manufacturing challenge that may still be showing up. -a- 1 1 Quote
Joe Larussa Posted January 31, 2022 Author Report Posted January 31, 2022 On 1/27/2022 at 11:38 AM, ArtVandelay said: How old is the ignition harness? They do deteriorate, with automobiles it usually shows up first when weather is wet, high humidity. About five years old Quote
Joe Larussa Posted February 6, 2022 Author Report Posted February 6, 2022 So this problem seems to be intermittent. On run up this morning, running rough on left side again. After checking twice decided not to fly. When I got back to the hangar I ran it up two more times and now it's back to normal. Couldn't afford to get stuck somewhere today so I scraped the flight. Wires are 520 hours old, mag overhauled 224 hours ago, spark plugs replaced with REM 38D's 136 hours ago. More suggestions appreciated. Quote
A64Pilot Posted February 6, 2022 Report Posted February 6, 2022 (edited) Most likely either the harness or the Mag. Do you have a engine monitor? If so keep running it on the mag that’s rough for awhile. the missing cylinder should run colder. If you don’t have a monitor, then do it with the cowling off and an IR thermometer will often find the “dead” cylinder. If it won’t isolate to one cylinder, then it’s more likely the Mag. I wouldn’t fly until I got it fixed, whatever it is, it’s not likely to get better in the air. Ignition in particular often gets worse with the engine at higher RPM and under load, higher cylinder pressure is harder to fire a plug Edited February 6, 2022 by A64Pilot 1 Quote
Joe Larussa Posted February 6, 2022 Author Report Posted February 6, 2022 40 minutes ago, A64Pilot said: Most likely either the harness or the Mag. Do you have a engine monitor? If so keep running it on the mag that’s rough for awhile. the missing cylinder should run colder. If you don’t have a monitor, then do it with the cowling off and an IR thermometer will often find the “dead” cylinder. If it won’t isolate to one cylinder, then it’s more likely the Mag. I wouldn’t fly until I got it fixed, whatever it is, it’s not likely to get better in the air. Ignition in particular often gets worse with the engine at higher RPM and under load, higher cylinder pressure is harder to fire a plug I do have a JPI 830 and have noticed cylinder 4 is running on average 25 degrees cooler than the rest. Never did that before. Changed both plugs in that cylinder with no change. Quote
Joe Larussa Posted February 7, 2022 Author Report Posted February 7, 2022 Well I did my first data download off my Jpi 830. Interesting info. Cylinder 4 running colder as well as large egt drop. 300 degree difference. Sent off the Savvy for analysis. 1 Quote
carusoam Posted February 7, 2022 Report Posted February 7, 2022 4 hours ago, Joe Larussa said: Well I did my first data download off my Jpi 830. Interesting info. Cylinder 4 running colder as well as large egt drop. 300 degree difference. Sent off the Savvy for analysis. lets see if we can get to the next level… upload the data to savvy, hit the share button, post the link here… If a cylinder skips a beat… it will be in the data… Make sure you have the fastest data gathering speed set up… it is in the 1-2 seconds per data point…. This will easily identify what cylinder… if it occurs during the run up, even better… PP thoughts only… -a- Quote
N9656G Posted February 7, 2022 Report Posted February 7, 2022 Question, After engine start are you leaning almost to engine shutdown? I find by doing this from startup/engine run-up it helps keep my plugs clean to the runup. You also may need you AP to adjust your mixture. Running to rich could cause this. In my CARB IO-530 in my old commahche 250 it would ALWAYS foul unless I leaned agressively after engine start. Now in my IO-360 fuel injected Lycoming in my M20J, it does not seem to be as much as an issue. When the rough engine happened during runup, did you attempt to run the engine up and lean aggressively to burn off plugs? Or just take back to hanger? Sounds like by the time you got back to hanger, the plugs burnt off all the gunk and you had a clean run-up after. Just my 2 cents worth 1 Quote
Joe Larussa Posted February 7, 2022 Author Report Posted February 7, 2022 https://apps.savvyaviation.com/my-flights/37091/4c4007f6-0d35-47cd-a363-176db4ac5403 Not sure if this is correct on sharing link. Might show all flights or just yesterdays. 2-6-22 will be the run up then shut down. Thanks in advance! 1 Quote
carusoam Posted February 8, 2022 Report Posted February 8, 2022 Joe, Great data share! Have a look at this… All of the flights showed up in that collection… But, I have copied the specific graph here… One EGT stands out more than the others… All four are trying to be very similar to each other… Except EGT4 is really behaving differently… Until about 00:16 then things look like they come back together…. EGT3 is a bit slow for the first two minutes, but it catches up with the two that are behaving nicely…. When EGT4 goes high… that is a sign that fuel is probably burning after the valve, flames getting past an unclosed valve… Oddly, I don’t see an R vs. L difference… as much as possibly a morning sickness type sticky valve…. A sticky valve might be keeping it from closing tightly, leading to no ignition happening during a few cycles… If there was a bad plug… it would really show up when running on the single mags… If there was a blocked fuel injector… it would fix itself, then come back on another day…. Let us know what Savvy says… Keep in mind, these are PP thoughts only… the Savvy guys are worth their weight in gold! Now you know you probably have something to look for in that cylinder… We can always compare other flights to see how long it takes for things to smooth out…. Best regards, -a- Quote
Joe Larussa Posted February 13, 2022 Author Report Posted February 13, 2022 (edited) For whatever it’s worth fixing the P-lead on the right mag seemed to fix the problem. Go figure Edited February 13, 2022 by Joe Larussa 3 Quote
carusoam Posted February 16, 2022 Report Posted February 16, 2022 Great follow-up Joe! Best regards, -a- Quote
Joe Larussa Posted February 22, 2022 Author Report Posted February 22, 2022 Well you just can’t make this up, but here goes. I thought the problem was fixed. Not so much. See if you can follow the bouncing ball. Approximately three years ago I had a mag failure leaving Monterey. Had the mag pulled and flew it home. Fun part was a ride home in a G3. Had mag overhauled and flew back with a A&P to reinstall. He had a hell of a time getting it to run correctly. Can’t recall why. Finally got it sorted and flew home. Fast forward to a few weeks ago when I started having rough engine on left mag. We found shielding on right side was grounding to main wire on P-lead. Couldn’t figure why that would make left mag run rough. Fixed leads and all normal for one flight. Next flight, left mag check not running rough but 150 RPM drop. Back to the drawing board. We decided to pull the mag and found the following. Mag cap was not indexed correctly and mag installed upside down. So all these years checking right was left and left was right. Capacitor on right side was toast and right points a little toasty. Purchased a overhaul exchange from Kelly Aerospace with two new capacitors and all is back to normal. 5 Quote
A64Pilot Posted February 22, 2022 Report Posted February 22, 2022 So the P leads were reversed? Yeah, that could cause troubleshooting problems Quote
Joe Larussa Posted February 22, 2022 Author Report Posted February 22, 2022 5 hours ago, A64Pilot said: So the P leads were reversed? Yeah, that could cause troubleshooting problems Yep! Quote
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