Bolter Posted October 10, 2019 Report Posted October 10, 2019 (edited) Today my engine was running a little rough. It would vibrate (felt like when I get into the no-run zone on the tach) for a few seconds, then clear up for 10 seconds or so, then return. After some basic steps to see if it would go away, I turned around and went home. My suspicion was a partially clogged injector on #3, which was leaning much earlier than usual. I got home, and removed #3 only, and blew out a little bit of softish material. Reassembled and could not recreate the problem. My only concern at this point, is that I was results-biased in my test flight. Does the funny recurring vibe match with a partially blocked injector? Some notes/observations in greater detail: Not sure when it started, but once I felt it, it was always there except as noted vibration would not change regardless of RPM (between 2300 and max) The JPI did not show any EGT or CHT that oscillated in any way mixture did not change condition, going from very ROP to LOP Boost pump did not change condition Normally I can run LOP smoothly easily, but it was extra rough when going LOP, and #3 cylinder EGT would drop out much sooner than the others Vibes existing in climb, just like in cruise Unsure of the problem, I climbed high (16500 to get ample glide distance) and the vibe problem stopped, fuel flow around 6.5 GPM at peak ADDED: I also made ROP and (slight) LOP mag checks in the air, and all plugs were firing. Taking note that at very low power things got better, I kept power levels low with throttle until landing. Vibes never came back. I went to runup area before parking, and found that if I ran higher RPM, closer to 2500, I could trigger the vibration, though it did not occur at regular runup conditions. I could not recreate vibrations afterwards, following the same procedure. thanks for your 2 cents, -dan Edited October 11, 2019 by Dan at S43 added item 9.
takair Posted October 10, 2019 Report Posted October 10, 2019 If you found material that you could actually feel and see in the injector, it very likely had some affect on your engine performance. Was the material in the actual “jet”/insert? It just doesn’t take much in there to make your engine run really poor. Not sure why the intermittent nature, but seems like it could do that too.
Bolter Posted October 10, 2019 Author Report Posted October 10, 2019 14 minutes ago, takair said: If you found material that you could actually feel and see in the injector, it very likely had some affect on your engine performance. Was the material in the actual “jet”/insert? It just doesn’t take much in there to make your engine run really poor. Not sure why the intermittent nature, but seems like it could do that too. Yes, the material piece came from the insert (smallest opening of the injector assembly). -dan
gsxrpilot Posted October 10, 2019 Report Posted October 10, 2019 I think you fixed it. It would make sense to me that it could be intermittent and only happen at certain power settings. At different fuel flows, there is more or less excess fuel anyway which could mask the issue. Good job troubleshooting and finding the issue.
carusoam Posted October 10, 2019 Report Posted October 10, 2019 Dan, How do you feel about downloading JPI data? By reviewing the data we can see where the challenge may have started... how bad it may have gotten... and if it is now cleared up... Got any pics of the dirt you washed out? Sometimes it may be recognizable by somebody around here... There are a couple of rubber bits in our fuel system that may show up downstream.... Some rubber hose inner lining seams to be one of the things... See how technically strong the MS community can be... PP thoughts only, not a mechanic. Best regards, -a-
Bolter Posted October 10, 2019 Author Report Posted October 10, 2019 (edited) 12 minutes ago, gsxrpilot said: I think you fixed it. It would make sense to me that it could be intermittent and only happen at certain power settings. At different fuel flows, there is more or less excess fuel anyway which could mask the issue. Good job troubleshooting and finding the issue. Thanks, Paul. I also guessed that low power meant lower fuel flows, and reduced the impact of a flow restriction creating the cyl-cyl variation. And can I get an Amen for engine analyzers! Edited October 10, 2019 by Dan at S43 added a thought 1
Bolter Posted October 10, 2019 Author Report Posted October 10, 2019 Just now, carusoam said: Dan, How do you feel about downloading JPI data? By reviewing the data we can see where the challenge may have started... how bad it may have gotten... and if it is now cleared up... Got any pics of the dirt you washed out? Sometimes it may be recognizable by somebody around here... There are a couple of rubber bits in our fuel system that may show up downstream.... Some rubber hose inner lining seams to be one of the things... See how technically strong the MS community can be... PP thoughts only, not a mechanic. Best regards, -a- I would love to share the JPI data, but mine does not record, and I have not gotten around to sending it back for repair. Only real time display works. I wanted to take a picture of the dirt, but lost it while getting the phone out :-( My thought was tank sealant, but it is hard to say. It was not metal or carbon. Just a fleck, like the size of the carbon you can get in the oil screen, but it could not be crushed into powder. 1
gsxrpilot Posted October 11, 2019 Report Posted October 11, 2019 1 hour ago, Dan at S43 said: And can I get an Amen for engine analyzers! AMEN! And knowing how to read them...
Bolter Posted November 6, 2019 Author Report Posted November 6, 2019 This is follow up to give closure to the issue. With around 5 hours over several weekends, in several different operating ranges (economy cruise, speed cruise, and formation flight) the problem remains gone. I feel that the small debris in the injector limited fuel flow and caused that cylinder to starve a little, creating the intermittent vibration. -dan
Guest Posted November 6, 2019 Report Posted November 6, 2019 We found this piece of debris in a fuel nozzle on a Piper Mirage, it was in the brass body below the stainless insert. The nozzle is the same style as a Bravo engine. Clarence
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