Stryk77 Posted August 17, 2021 Report Share Posted August 17, 2021 Hey everyone, I had an interesting flight on this past Saturday, here in Montreal Quebec, and although the aircraft is in maintenance as we speak, I thought it would be a good idea to get some feedback from you owners. My plane is 1979 Mooney M20K 231 with the 262 Trophy conversion. Saturday: My mechanic changed the Right magneto for a brand new one on Friday. The RPM 's on the ground were really good and stable. Run up was nice, with a 75rpm drop with the mags from both (from 1700rpm). On the initial climb (Turbo TSIO-360-MB4 - 36'' / 2700rpm), everything felt good. I leveled off at 2000ft and pulled the power back (29"/2600rpm). Then, I was cleared for 5500ft, proceeded to applying full power gently and climbing with roughly (35" / 2670rpm) in a Vy speed (96kts) climb. Everything looked great until 4000ft when I had a major drop in RPM, rough engine running, loss of airspeed and cylinder 5 was indicating a temp drop in both CHT / EGT at the same time. Cyl 5 showed a dead EGT and never came back, but the CHT dropped and back to normal when coming back to the approach. Bare in mind, I was still within 5nm of airstrip, with Terminal. Once pulling the power below 18", everything felt normal. There also was not any change in engine sound, the engine sounded like it was still running on 6. On the ground, I was able to land and taxi back, no issues as engine ran smooth., I even did run up with mag check after flight, both were spot on. I am uncertain what has happed, but had to rush back to the field and park the aircraft. The initial thoughts when everything failed, was "Did I lose a mag?", that feeling. Sunday: I sent all details from the JPI EDM 700 to Savvy Aviation and they came back with some ideas pointing towards induction leaks. Monday: Good thing about having a hangar at a maintenance facility !! Team of experts were on it, this is what we did. 1) Checked all fuel nozzles, removed and inspected. Did a pump out test to see equal spray amount. Everything good. 2) Ignition tests, checked spark plugs and cables, Everything good. 3) Ran a borescope into cylinder 5, everything looked good. 4) Removed the valve cover, a checked rocker position, removed rocker and inspected valves. We thought maybe a valve a stuck, negative in the findings. Everything good. 5) Induction test, we checked all possible induction leaks, found no issues. 6) Wastegate / turbo function. We ran the borescope into the wastegate, manually checked the function, all good. Ran the borescope into turbo, all looked fine. Our last option yesterday was to remove the mags and inspect them, that is where we are at. The last uploaded file was not a flight, it was a run up mid day with my tech to see if we can replicate the issue. Everything ran very smooth... Green line (EGT5) taking a flat dive and never coming back until engine off. During a runup test on Monday, EGT5 was back online, like normal. Let me know what you all think! Thanks. Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted August 17, 2021 Report Share Posted August 17, 2021 I have seen plugs short and misfire when hot, but as of course we have two that should not make a cylinder go dead, just a reduction in power. Of course capacitors in a magneto can also quit when hot, but that would be all cylinders, not just one. An induction leak under boost to completely kill a cylinder would I assume be a very large, easily found leak. Valves have been known to stick intermittently, ref Lycoming morning sickness as an example, so just a guess, that’s mine, but it’s just a guess. 1 Quote Link to comment Share on other sites More sharing options...
David Lloyd Posted August 17, 2021 Report Share Posted August 17, 2021 A blocked injector could do that. Sometimes they clear themselves. Is that #3 CHT jumping around a bunch? Might check the connections for that. Quote Link to comment Share on other sites More sharing options...
DXB Posted August 17, 2021 Report Share Posted August 17, 2021 Interpreting the engine monitor : (1) Some kind of #5 cylinder malfunction causes rough running engine and anomalous rapid rise in CHT but no clear effect on EGT one hypotheses: A glowing carbon deposit causing intermittent pre-ignition? I'm having a hard time figuring out what could raise CHT so dramatically but have no effect on EGT. (2) upon reducing power to land, #5 CHT plummets and EGT flatlines, meaning zero combustion in that cylinder - makes no sense to me in context of my hypothesis to explain #1. (3) There is clearly something wrong with the #5 EGT sensing upon landing - Combustion seems to recover around 00:22. On the ground, CHT trace for #5 acts like all the rest, but #5 EGT trace remains flatline. Did whatever temporarily killed combustion in malfunctioning #5 cylinder somehow also permanently kill the EGT probe?? Interesting case.... Quote Link to comment Share on other sites More sharing options...
DXB Posted August 17, 2021 Report Share Posted August 17, 2021 28 minutes ago, David Lloyd said: A blocked injector could do that. Sometimes they clear themselves. Is that #3 CHT jumping around a bunch? Might check the connections for that. A partially clogged injector would explain the rapid rise in #5 CHT and running rough - but how could that happen without an effect on EGT? Quote Link to comment Share on other sites More sharing options...
Stryk77 Posted August 17, 2021 Author Report Share Posted August 17, 2021 I’m on the same page with all of you on this. what throws me off is the dead EGT but still having combustion to make the landing. Engine was for sure running on six (sound wise). yesturday when we did some ground checks and full WOT run up, EGT probe for cyl 5 was functional. Weird.. Quote Link to comment Share on other sites More sharing options...
slowflyin Posted August 17, 2021 Report Share Posted August 17, 2021 I had a plugged injector recently. Engine ran normally at a lower power setting on the approach. I speculated enough fuel was getting by at the lower setting. Not sure about the dead egt. Quote Link to comment Share on other sites More sharing options...
David Lloyd Posted August 17, 2021 Report Share Posted August 17, 2021 3 hours ago, DXB said: A partially clogged injector would explain the rapid rise in #5 CHT and running rough - but how could that happen without an effect on EGT? Yep, you're correct. We all have good theories looking at either EGT or CHT but not both at the same time. Quote Link to comment Share on other sites More sharing options...
Warren Posted August 17, 2021 Report Share Posted August 17, 2021 This one is confusing. Random speculation here: Have you inspected the thermocouple leads ? Any chance CHT5 and EGT5 are too close to the exhaust and getting overheated/melted intermittently? Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted August 17, 2021 Report Share Posted August 17, 2021 I don’t know how you can explain the drop in RpM, speed and rough running with an indicator problem, Rough running and loss of power means something actually happened, a clogged injector could do it. Prop governor should have recovered the RPM rapidly though. Quote Link to comment Share on other sites More sharing options...
Warren Posted August 18, 2021 Report Share Posted August 18, 2021 My thoughts are that the CHT indicated high before the engine ran rough. Then the rough running - I agree something happened here. Suddenly no traces of any problems and it all runs fine again. -lean mixture due to fuel injector partial blockage would have shown a change in EGT. -maybe light detonation or preignition could also explain this but I would expect lower EGT's. -maybe much higher friction for some reason, break-in certainly causes higher CHT. No real idea. Just thought it would be easy to look at the thermocouples and rule out a potential indication problem. Quote Link to comment Share on other sites More sharing options...
carusoam Posted August 18, 2021 Report Share Posted August 18, 2021 Bummer… I couldn’t get access to the data to look closer…. It really helps to click the share button at Savvy, and copy the link here… Or we are all stuck seeing the exact same thing…. Which might not be where the problem is hiding… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
carusoam Posted August 18, 2021 Report Share Posted August 18, 2021 CHT5 and egt5 are both misbehaving…. A sign that something is up, not just a bad sensor… Single cylinder problems are typically a blocked fuel injector… For FI flow test… that is when the baby food jars come out… identical clear containers catching the flow of fuel for a timed period… If they all flow the same… not the problem… If one is blocked, it is marked FI5…. Air doesn’t usually block a single cylinder… Mags aren’t capable of ignoring a single cylinder… valve’s usually have a different fingerprint when failing… got any pics of the valves? If a valve sticks open, the EGT starts to rise… CHT will drop… before going dead from lack of compression… Looks a lot like fuel injector issue…. Or fuel distribution issue… how old is that spider? PP thoughts only, helps to have more data… multiple prior flights if available… run-up data always help… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Stryk77 Posted August 18, 2021 Author Report Share Posted August 18, 2021 Hi everyone, Got the mags checked and they are 100% OK. Cleared that off the ckecklist! I am also narrowing it down to the injector being partially or completely blocked causing a momentary loss of combustion. Will be running more tests today and a test flight. Everything that's a vital piece on the engine is new within the last 6 months. Thanks! Quote Link to comment Share on other sites More sharing options...
LANCECASPER Posted August 18, 2021 Report Share Posted August 18, 2021 Seems way too strange that the first flight after a mag replacement this happens. It happens at higher altitudes then clears up at lower altitudes. These are pressurized mags right? Brand new mags have been known to be defective out of the box. 1 Quote Link to comment Share on other sites More sharing options...
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