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Thread: IO-520 Low Idle and Stumbles

  1. #1
    behindpropellers's Avatar
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    IO-520 Low Idle and Stumbles

    Chasing this right now:

    IO-520A Rebuilt Mags and New Engine controls.

    1. Idle is low.
    2. When advancing throttle it stumbles before catching up.


    Informed guess: Previous throttle cable was adjusted to give the correct idle RPM. Fuel flow is not up to spec on the low end.

    Gauges go on the fuel system next week...

    Tim

  2. #2
    www.SkupTech.com mike mcs repair's Avatar
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    yes step one, get fuel high & low pressure correct, to high end of range on high.(well at least for sea level)

    get it to idle as low as it will stay running, if you got a good cam this can be down to ~350, you should see a little black smoke out of exhaust when mixture is correct at this low idle, not that you idle it that low always, but helps for landing..

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    Just just went through this on my 520. Sounds like your idle mixture is to lean. Do you get a small rise as you cut the mixer? If not, to lean. This will cause a stumble when advancing throttle from idle..
    check your high and low fuel pressure, adjust idle and idle mixture. Then you should b good..


    Quote Originally Posted by behindpropellers View Post
    Chasing this right now:

    IO-520A Rebuilt Mags and New Engine controls.

    1. Idle is low.
    2. When advancing throttle it stumbles before catching up.


    Informed guess: Previous throttle cable was adjusted to give the correct idle RPM. Fuel flow is not up to spec on the low end.

    Gauges go on the fuel system next week...

    Tim

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    If I remember correctly, the manual I have says set the rpm at 1000. Slowly pull the mixture out to almost cutoff. As you lean, the rpm shud increase about 50 rpm, then decrease. This shud give you a quick idea of how to adjust the mixture.

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    Clean the injectors, I use Hoppies #9 in an ultrasonic hot pot. Mine really hesitates and won’t come off idle unless you baby it if the injectors have more than say 250-300hrs since the last cleaning. Also if you are getting a little fuel drip out of the injection vent line after shut down the flow divider may need a rebuild, just had that done.
    Last edited by OLDCROWE; 11-13-2017 at 05:50 AM.
    Remember, These are the Good old Days!

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    behindpropellers's Avatar
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    Thanks Kirby!

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    Quote Originally Posted by charlesf View Post
    If I remember correctly, the manual I have says set the rpm at 1000. Slowly pull the mixture out to almost cutoff. As you lean, the rpm shud increase about 50 rpm, then decrease. This shud give you a quick idea of how to adjust the mixture.
    This is standard procedure for ALL engines for determining idle mixture setting, not just the big Continentals.
    N1PA

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    Steve Pierce's Avatar
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    Quote Originally Posted by OLDCROWE View Post
    Clean the injectors, I use Hoppies #9 in an ultrasonic hot pot. Mine really hesitates and won’t come off idle unless you baby it if the injectors have more than say 250-300hrs since the last cleaning. Also if you are getting a little fuel drip out of the injection vent line after shut down the flow divider may need a rebuild, just had that done.
    Had an IO-520 in a C210 that I had to clean the injectors every 100 hours or it would hesitate like that.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
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    behindpropellers's Avatar
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    This is the screen in the fuel control unit.

    FCU Strainer.jpg
    Thanks Dave Calkins, N86250 thanked for this post
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    Quote Originally Posted by behindpropellers View Post
    This is the screen in the fuel control unit.

    FCU Strainer.jpg
    Yuck, I hate it when a filter does its job!
    Remember, These are the Good old Days!
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  11. #11
    Steve Pierce's Avatar
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    What the heck is coming apart?
    Steve Pierce

    Everybody is ignorant, only on different subjects.
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  12. #12
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    What the heck is coming apart?
    Clean recheck. Repeat, repeat

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    Quote Originally Posted by Steve Pierce View Post
    What the heck is coming apart?
    Maybe, some line guys fleece hoodie...
    Remember, These are the Good old Days!
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  14. #14
    Steve Pierce's Avatar
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    Quote Originally Posted by OLDCROWE View Post
    Maybe, some line guys fleece hoodie...
    I doubt it, several other screeens prior to that one that would catch a line guy's hoodie.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
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  15. #15
    cubdriver2's Avatar
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    Looks like a Scotch Brite pad?

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

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    behindpropellers's Avatar
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    I'm leaning toward pulling the whole injection system off and sending it in for IRAN....

    Thoughts?
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  17. #17

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    That’s more junk on the screen than I’ve seen in 5+years combined on mine. I’m with Steve, what’s coming apart or got in the system, as I understand the system that’s the last chance screen.

    How long has it been since the last cleaning?
    Remember, These are the Good old Days!

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    behindpropellers's Avatar
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    Quote Originally Posted by OLDCROWE View Post
    That’s more junk on the screen than I’ve seen in 5+years combined on mine. I’m with Steve, what’s coming apart or got in the system, as I understand the system that’s the last chance screen.

    How long has it been since the last cleaning?
    I'm going to call the last guy who did the annual and ask him about it. There actually is one more screen, in the fuel divider.

    Any favorite continental fuel injection shops you guys recommend?

  19. #19
    Steve Pierce's Avatar
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    from the Rolodex:
    Mike's Fuel Metering
    9406 East 46th Street North
    Tulsa, OK 74117
    918-838-6217

    Been a while since I did anything fuel injected but he was good to me.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  20. #20

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    Quote Originally Posted by behindpropellers View Post
    I'm going to call the last guy who did the annual and ask him about it. There actually is one more screen, in the fuel divider.

    Any favorite continental fuel injection shops you guys recommend?
    Mike's Fuel Metering in Tulsa, they did my flow divider a few weeks ago (very prompt) and I understand they do most of the big Tulsa engine shops work.

    https://www.facebook.com/pages/Mikes...60348510651941
    Remember, These are the Good old Days!

  21. #21

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    Quote Originally Posted by Steve Pierce View Post
    from the Rolodex:
    Mike's Fuel Metering
    9406 East 46th Street North
    Tulsa, OK 74117
    918-838-6217

    Been a while since I did anything fuel injected but he was good to me.
    HA!
    Last edited by OLDCROWE; 11-28-2017 at 11:14 AM.
    Remember, These are the Good old Days!

  22. #22
    www.SkupTech.com mike mcs repair's Avatar
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    since that filter is after gascolator & screen, I would say, start with the gascolator to determine the screen in it is not damaged, to have let all that by.... never seen that much downstream...

  23. #23
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    I had the carb inlet screen (aka last chance filter) clog once in my old C170 ragwing.
    This was downstream of both the screen in the gascolator and the screen in the engine-driven fuel pump.
    Itty bitty red fibrous debris, looked like someone dropped a red shop rag in the fuel tank and it slowly dissolved.
    Cessna Skywagon-- accept no substitute!

  24. #24
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    Quote Originally Posted by hotrod180 View Post
    I had the carb inlet screen (aka last chance filter) clog once in my old C170 ragwing.
    This was downstream of both the screen in the gascolator and the screen in the engine-driven fuel pump.
    Itty bitty red fibrous debris, looked like someone dropped a red shop rag in the fuel tank and it slowly dissolved.
    Drained the tanks and I am starting there....should be interesting.

    Tim
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  25. #25
    behindpropellers's Avatar
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    Pulled the gascolator last evening, not much in it as far as debris. Right header was clean. Left header had some water and gunk in it.

    Tim
    Thanks Bill Rusk, OLDCROWE, Charlie Longley thanked for this post

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