0-235-C1 Engine died on roll out

Discussion in 'Maintenance Bay' started by Lndwarrior, Jun 24, 2022.

  1. Lndwarrior

    Lndwarrior Line Up and Wait

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    Engine is an O-235- C1 with an MA3A carb., without the primer pump.

    Flown almost 600 hours and never happened before, and now its happened twice in two flights. Not flying it until I can figure this out.

    I just finished a very comprehensive condition inspection.

    I did replace the fuel filters.

    I did not check the fuel pressure afterwards because I didn't think of it at the time.

    100 hours on new mags.

    Checked timing on condition inspection and it was spot on.

    No changes to prop or settings.

    No change to approach and landing procedure. Carb heat full, mixture just slightly leaned. Same as I have been doing for 600 hours.

    In both cases the engine died when I pulled the throttle to idle as I was rolling out. In both cases it started right up afterwards.

    I did find a small fuel leak at tge carb and fixed that.

    I did adjust the idle and mixture settings and it seemed to run smoother at idle. Also got a small rpm drop (not the often repeated 50 rpm though) on slowly pulling the mixture to cutoff.

    Thought the combination of the two items fixed the problem. It didn't. Same thing happened on rollout after the test flight. And again, it started right up after dying and ran fine to the hangar.

    I would appreciate any and all troubleshooting ideas.
     
  2. geezer

    geezer Line Up and Wait

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    I have had a leaned engine die at idle, after landing. I now land full rich.

    The fuel pump would be my second test.
     
  3. Salty

    Salty Touchdown! Greaser!

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    This time of year, I’d guess the opposite, too rich for the heat and humidity. Maybe need to adjust idle mixture and lean it more.
     
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  4. Bell206

    Bell206 Final Approach

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    Verify your carb heat system is functioning properly. Is this a standard heat cuff or a homebuilt cuff?

    What is the idle RPM?

    Your mixture setting should show a 25 RPM rise while pulling to cutoff if I recall correctly not a decrease.
     
    Last edited: Jun 25, 2022
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  5. mondtster

    mondtster En-Route

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    I've had a couple of engines die on me in a similar fashion where nothing wrong could be found and the problem could not be replicated. In those cases, the only thing that makes sense is that there was some carburetor ice. Your case sounds a bit different however, as it sounds like the problem can be repeated. Perhaps there is a vacuum leak causing a lean mixture at small throttle openings. Was anything in the induction system disturbed while the other work was completed?
     
  6. Daleandee

    Daleandee En-Route

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    Vapor lock? Is all of the shielding in place to keep the lines and gascolator cool? :dunno:
     
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  7. Lndwarrior

    Lndwarrior Line Up and Wait

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    I misspoke in my post. I meant to say a slight increase, about 25 rpm.

    Idle rpm is right at 700 which is a little higher than what I was running before the problem came up and I adjusted the carb. Previously idle was about 650.
     
  8. Lndwarrior

    Lndwarrior Line Up and Wait

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    I have all my fuel lines insulated. I think this would have cone up in the previous 600 hours. But I appreciate the ideas!
     
  9. Lndwarrior

    Lndwarrior Line Up and Wait

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    I have an electrically dependant engine with two electric fuel pumps in series. Both pumps are on in landing and takeoff phase.

    I always check the fuel pressure rise when I switch on the fuel pump before landing. I've noticed no anomalies with the fuel pressure.

    Thx for taking the time to try and help. I appreciate it.
     
  10. Lndwarrior

    Lndwarrior Line Up and Wait

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    I went and took another look at the induction system today. All new gaskets last year and I checked the torque on the bolts at the recent condition inspection. I still have some more investigation to do on this. Though I would think an induction leak would also cause an issue during my pre-takeoff idle check.
     
  11. Doug Reid

    Doug Reid Cleared for Takeoff

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    When are you turning off carb heat....short final or after landing ?
     
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  12. mondtster

    mondtster En-Route

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    The fact that you mention that the idle is a little higher now still has me suspicious that there may be an induction leak. But if nothing changed and nothing is really obvious that might not be the problem.

    Do you have a manifold pressure gauge? Did the reading you get at idle/warm up change after the recent service?
     
  13. Lndwarrior

    Lndwarrior Line Up and Wait

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    No mp gauge. No vacuum system on my homebuilt.
     
  14. Lndwarrior

    Lndwarrior Line Up and Wait

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    After landing, on roll out. Probably just before it dies, now that I think about it.
     
  15. mondtster

    mondtster En-Route

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    If there is a correlation between the carb heat removal and the engine dying I would be checking the air box to make sure there isn’t a restriction.
     
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  16. geezer

    geezer Line Up and Wait

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    Carb heat adds a restriction to the air flow ahead of the carburetor, and as such, enriches the mixture.

    A cruise leaned mixture, enriched by carb heat, might run fine on final, but quit when the heat is removed, especially since wind is not driving the propeller to a higher induction air flow than after landing..
     
  17. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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    Check the idle mixture. This is unaffected by the red knob (well until you get to ICO). If it is excessively rich it can cause the engine to die at idle when hot.
     
  18. Dan Thomas

    Dan Thomas Final Approach

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    It adds minimal restriction, and for many, it reduces the restriction by taking the air filter out of the flow. The real reason for enrichment is the reduced density of the heated air, and since the carburetor senses velocity, not density, the warm airflow gets the same amount of fuel as the cold air did, and the mixture gets richer.
     
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  19. Dan Thomas

    Dan Thomas Final Approach

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    Do as Lycoming says. Works better.

    upload_2022-6-25_10-43-23.png
    upload_2022-6-25_10-45-30.png

    From the manual for that engine, produced by the manufacturer: https://www.lycoming.com/sites/default/files/O-235&O-290 Operator Manual 60297-9.pdf

    A 25 RPM drop is for injected systems. You have a carb.
     

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  20. MauleSkinner

    MauleSkinner Touchdown! Greaser!

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    I had an engine do that a few times…turned out it was a plugged fuel tank vent. Created vacuum in the tank when I was flying under power, sucked the fuel back and vapor locked it when I went to idle for landing. (The go around was ugly.)
     
  21. Lndwarrior

    Lndwarrior Line Up and Wait

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    Yep, checked my vents yesterday, including borescoping the inlet inside the tank. They're all clear.
     
  22. Lndwarrior

    Lndwarrior Line Up and Wait

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    That's good to know. The challenge is figuring out how to accomplish this. I've spent a long time adjusting the carb to try and get to this but it hasn't happened. Also, prior to the current issue, I was already getting about the same 25 rpm rise.

    Also, I'm at 3000 ft elevation and the DA when I'm working on the plane is probably closer to 4000 ft, so where the exact number should be is hard to determine. I am going to give this one more try, perhaps early in the morning before it gets too hot. PITA making a minor adjustment, then climbing in the low wing plane, over and over again, especially when you have a bad back.... %^)
     
  23. Lndwarrior

    Lndwarrior Line Up and Wait

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    This is the case in my plane. It has a very short carb heat inlet from a half-open heat muff. Definitely less resistance than pulling thru the air filter.
     
  24. Lndwarrior

    Lndwarrior Line Up and Wait

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    I will check this.
     
  25. Dan Thomas

    Dan Thomas Final Approach

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    Picture of the heat muff? Lycomings don't typically need much heat, but those open muffs are pretty inefficient.

    Another clue would be the temperature and dewpoint at the time this is occurring. Small differences between means much more likely carb icing. Lycomings can and will ice up. I've had it happen often enough.

    upload_2022-6-25_14-43-37.jpeg
     
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  26. Dan Thomas

    Dan Thomas Final Approach

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    It occurred to me that there is one more thing to check. The primer. Is it in and locked? Or is it defective? With the throttle closed, the intake manifold's pressure is low (high suction) and a leaking or unlocked primer will let a lot of fuel be sucked into the manifold, flooding the engine, and it could die on rollout.

    This is a primer plunger. See that pointed needle on the right-hand end? That is spring-loaded, and it fits into the fuel outlet at the bottom of the primer cylinder, to make sure no fuel is sucked by the engine through the primer. If there is something in that tiny hole preventing seating of the needle, or if the spring is broken, or if the primer plunger isn't all the way in and locked there, fuel can and will flow through it.

    upload_2022-6-26_8-45-25.jpeg
     
  27. Magman

    Magman Line Up and Wait

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    The Primer may well be the culprit here. Closing the throttle on final should cause very low Manifold Pressure ( High Vacuum) with the prop windmilling. If the Primer is not seating ( see previous post) a overly Rich mixture can result. It might be difficult to duplicate this on a static run-up.

    My thought would be to disconnect the Primer System forward of the firewall for a test. Capping/ plugging the lines would be good practice. Note that lines on aircraft are flared to 37 degrees so finding proper ones might not be easy. The Primer nozzles have a small jet ( .015? ) so the amount of air from that source should be negligible. Auto parts houses have cap/plugs in 45 degree brass which should suffice for test purposes.
     
  28. Lndwarrior

    Lndwarrior Line Up and Wait

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    That is a good thought but I have an electric primer system. It is possible the solenoid is not closing all the way.

    Something else to check.
     
  29. Lndwarrior

    Lndwarrior Line Up and Wait

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    To close out this thread, I finally fixed it.

    Originally I think I had some fear of the idle/mixture knob. Possibly from some early bad experiences adjusting an auto carb. I was very tentative and only making very minor adjustments.

    Yesterday I got more aggressive with it. Went back and forth a number of times until, I started to get closer. I was doing this by myself so at each adjustment I had to shut down the engine, make the adjustment, climb back in the plane and restart.

    Finally it started getting closer to both the 700 rpm target and I started to see a rise in rpm when pulling the mixture. The last few adjustments were about 1/8 of a turn. Restarted the engine, idle was at 700 rpm and I got the full 50 rpm rise on shutdown.

    Went for a test flight over the runway. It ran fine. Went to altitude and it leaned properly, landed and it ran fine all the way back to the hangar.

    The single knob on the MA3A carb means there is only one spot where the rpm and mixture control align perfectly.

    Just posting this for the possible future benefit of others.
     
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  30. DFH65

    DFH65 En-Route

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    Check make sure your intake is tight and there are no leaks. At lower RPM it may be getting too much air.
     
  31. Dan Thomas

    Dan Thomas Final Approach

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    Nope. Idle RPM is set with a throttle stop screw. Look for it on the carb body next to the throttle lever. Idling too high can lengthen the landing roll and is harder on the brakes.

    Edit. I tried to paste the picture earlier. Didn't work. Trying it again:

    upload_2022-6-28_14-30-27.png
     
    Last edited: Jun 28, 2022
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  32. Lndwarrior

    Lndwarrior Line Up and Wait

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    Did a full intake system leak test. No leaks.