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  #21  
Old 01-18-2021, 01:56 AM
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rv8ch rv8ch is offline
 
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Not sure if you mentioned this, but have you had a chance to upload your engine monitor data to savvy? They might be able to provide some hints based on those graphs. What kind of FI do you have? Air filters clean? Perhaps turn off your squelch on your headset to see if you hear any popping - that could indicate a spark plug wire that has a small break in it which only appears from time to time. Any consideration of getting an enginebridge or a eicommander to see if your timing on the pmags looks good during this lean test?
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  #22  
Old 01-18-2021, 05:55 AM
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  #23  
Old 01-18-2021, 08:31 AM
Lt Dan Lt Dan is offline
 
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Quote:
Originally Posted by rv8ch View Post
Not sure if you mentioned this, but have you had a chance to upload your engine monitor data to savvy? They might be able to provide some hints based on those graphs. What kind of FI do you have? Air filters clean? Perhaps turn off your squelch on your headset to see if you hear any popping - that could indicate a spark plug wire that has a small break in it which only appears from time to time. Any consideration of getting an enginebridge or a eicommander to see if your timing on the pmags looks good during this lean test?
Good question regarding the engine data. This airplane has Electronics International engine gauges. I’m not a fan at all. The EGT/CHT is provided by the UBG-16. I found a serial port under the panel and attempted a data download, but it seems that this panel was not built with a data recorder. It’s located opposite the engine gauges closer to the autopilot. Any ideas what that random serial port could be if not for a data downloader?

I believe it’s stock fuel injection that came with the IO-360-M1B new about 600 hrs ago. That was going to be my next route. From the outside, they appear somewhat dirty. But I’m not so savvy on fuel injector nozzles. I need to do some more homework before I pull them and investigate.

As for the enginebridge or eicommander, similar story. I don’t know much about those. I’ll have to look into it. Could anyone provide a snapshot of insight as to what is involved installing one of those?

Thanks!!
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  #24  
Old 01-18-2021, 08:59 AM
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I think you’re going through this the right way - tune up every piece of the engine and accessories until you find the problem. Sounds to me like you’ve nailed down the ignition - now clean the fuel injectors and see what that does.
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  #25  
Old 01-18-2021, 07:39 PM
Lt Dan Lt Dan is offline
 
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Thanks Paul. You guys have all been great.

I'm thinking in terms of what could possibly cause a periodic and almost rhythmic hiccup. Are there moving parts inside the flow divider? I did some preliminary reading and sounds like it has a diaphragm. Do these things ever need to be rebuilt? Not jumping to conclusions, but how does one test the condition of their flow divider?
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  #26  
Old 01-18-2021, 09:26 PM
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I don’t know what brand injection system you have, but there’s a final filter near the inlet of the fuel control that should be checked annually. I had an issue with my AFP divider when it got some gunk in one of the metering slots. AFP(Airflow Performance) has a field instruction on how to clean it if that’s the type you have. YMMV. Bob
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  #27  
Old 01-31-2021, 08:15 PM
Lt Dan Lt Dan is offline
 
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Default More Data

I was able to run two test profiles today in hopes of gathering more data. I have to gather it all manually, as I have an EI UBG-16 but no recording capability. Long story short, I believe it points more towards the fuel system, though I could use some help. Questions in bold.

Mike Busch's Induction Leak Test:

My EGT drop between high power (25" MAP) and low power (15" MAP) were: 89, 109, 72, and 95 deg F (cylinders 1-4 respectively). I know they are supposed to fall uniformly and if not you can suspect an induction leak. What Mike doesn't say is what is "normal." I figured my EGTs would fall more uniformly (for example, all by 100 +/- 2 deg). Instead, the fall was about +/- 20 degrees. Is this a normal spread?


GAMI Lean Test:
12,500 ft, 65% power.

Now here's where I'm suspecting the fuel system. To start the test, you go to full rich. I recorded the fuel flow at 12.4 GPH. When I looked back at the gauge after recording the value, it had jumped to 14.0 GPH and then settled back down and remained at 12.4 GPH.

I thought this was strange. I did not detect any change in power, nor note any change in MAP or EGT. (It may have very briefly occurred but I don't have recording capability.) Therefore I suspected the fuel flow sensor may be going bad. However, I doubt that's the case, as after any cross country, I can reliably fill the tanks to within 0.1 gal of what's reported by the totalizer.

As for the test, I slowly reduced fuel flow with the mixture control, moving it towards lean in the smallest increments I could and counting to 15 in between movements. The first time I did the mixture sweep, all cylinders simultaneously peaked at 7.1 GPH. A GAMI spread of 0.0.

Upon repeating the test, the first cylinder peaked at 7.4 GPH and while I was recording data, the fuel flow rapidly fell off to 7.1 and the EGT gauge was showing that all cylinders had peaked. This was without any further movement of the mixture control.

I threw out that sample and repeated. On the third attempt, the first cylinder peaked at 7.5 GPH and before I could remove my eyes from the gauge, I watched the fuel flow rapidly drop off to 7.1 and all cylinders again indicated they had peaked.

Now I suspect that my fuel servo may be going bad. The mixture has always be extremely, extremely stiff on the ground prior to start and I suspected that it was the cable, but now I think that the fuel servo may be suspect.

Next time I pull the cowl, I will check the previously mentioned things (injectors and flow divider), as well as the mixture cable, and the fuel servo control linkages. I'll gather more data on what setup I have and report back, but I'm pretty sure it's whatever comes stock with an IO-360-M1B new from Lycoming in 2004 (Precision Airmotive?).

Are there known failure modes of the fuel servo that can explain the behavior described above?
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  #28  
Old 02-01-2021, 02:51 PM
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Quote:
Originally Posted by Lt Dan View Post
it seems that this panel was not built with a data recorder. It’s located opposite the engine gauges closer to the autopilot. Any ideas what that random serial port could be if not for a data downloader?

Thanks!!
If you have a serial port, there is probably a "black box" stuffed in a corner somewhere. I keep a very old laptop around and a serial to usb adaptor just to handle this. The system predates the ubiquitous thumb drives most systems use now. http://befcstl.org/wp-content/upload.../OI-II-MUX.pdf

Good luck!
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  #29  
Old 02-06-2021, 11:36 AM
Lt Dan Lt Dan is offline
 
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Quote:
Originally Posted by nomocom View Post
If you have a serial port, there is probably a "black box" stuffed in a corner somewhere. I keep a very old laptop around and a serial to usb adaptor just to handle this. The system predates the ubiquitous thumb drives most systems use now. http://befcstl.org/wp-content/upload.../OI-II-MUX.pdf

Good luck!
That is what I thought, too. However, there's no "Record" Light on the panel, nor is there a Data Recorder Control Switch ("Burst/On/Download") located anywhere on or behind the panel. I even went so far as to hook up my old computer to the serial port via adapter with EI's software, but it requires you to switch the switch to "Download" in order to pull data. Unless I'm missing something, there's no way to get data without that switch...
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  #30  
Old 02-06-2021, 11:37 AM
Lt Dan Lt Dan is offline
 
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Quote:
Originally Posted by Lt Dan View Post

Mike Busch's Induction Leak Test:

My EGT drop between high power (25" MAP) and low power (15" MAP) were: 89, 109, 72, and 95 deg F (cylinders 1-4 respectively). I know they are supposed to fall uniformly and if not you can suspect an induction leak. What Mike doesn't say is what is "normal." I figured my EGTs would fall more uniformly (for example, all by 100 +/- 2 deg). Instead, the fall was about +/- 20 degrees. Is this a normal spread?
Still wondering if anyone else has conducted an induction leak test with whom I can compare data.
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