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Thread: O-290 Quit on Rollout & Hard Starting

  1. #1
    Captain Ron's Avatar
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    O-290 Quit on Rollout & Hard Starting

    Hi Folks,

    On my last few flights I've had a bit of trouble getting it started using the procedure that has otherwise worked for years (three shots of primer after feeling it firm-up, throttle cracked). I brushed that off since my primer has been getting a bit weak and each time it was after a period without running so the battery was possibly a bit low. Went flying this past Sunday after servicing the battery and with a solid primer and it started up without issue. Had a great flight but as I was enjoying a rare greaser of a landing it quit on the rollout. Naturally at this point the primer refused to pump (I might start a thread on that) but I was able to get it started with the accelerator pump. Taxied back to the hangar and it idled without issue. Possibly not as smoothly as could be but certainly nothing abnormal with or without carb heat. So now I'm wondering if the hard starting and the flameout are related.

    I did a search here (and online in general) and found an old thread on the same thing for a C85 that mentioned the issue was corrected with a turn of the idle mixture screw. Unfortunately I didn't make a point of looking for the RPM rise as I shut down but I will do next time I'm out there.

    So, short of checking for induction leaks and idle carb settings does anybody have any ideas what to check? I can see where the idle adjustment might work but I'm puzzled why this would manifest itself only recently. And what would be different about the rollout compared to sitting in front of the hangar?

    Cheers,

    Jeff

  2. #2
    CamTom12's Avatar
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    Is your primer leaking, maybe?

  3. #3
    www.SkupTech.com mike mcs repair's Avatar
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    Out of gas, almost???


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    Carb needs cleaning?

  5. #5
    algonquin's Avatar
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    Impossible to trouble shoot something like this on the internet. Your going to get lots of real possibilities but that will have you shotguning you all over the place? Sit down and make a chart for yourself of thing that will cause a engine to do what yours is doing. Pick one and only one, work a-z on that. If you don't find anything pick another. You have fuel and electric.
    Ex sample: primer system; fuel to carb;carb.; spark plugs;wires; mags; ING. Switch; intake;xhaust system and muffler; compression. One at a time and you will find the problem. Good luck and if you find something strange in a system ask about it and you will be on the road to fixing or understanding it.
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  6. #6

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    Fuel level and right or left tank?



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  7. #7
    PerryB's Avatar
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    It COULD be a lot of things, but the primer would be my first suspect.
    After Monday and Tuesday, even the calendar says WTF !

  8. #8
    Captain Ron's Avatar
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    Thanks Guys! I did have lots of fuel (1/4 in the right tank, >3/4 in the left tank, left tank selected for landing). I also thought maybe the tank vents were obstructed but I could easily blow though the caps and had lots of fuel flow at the fuel bowl with the drain open.

    I like the idea of the primer leaking/failing since it is a common link between the symptoms. What's the easiest way to check if it is leaking? Remove it and pressurize with air or try to pump some fuel from a jar or what? Need to figure out how to disassemble the thing (old Imperial Brass Co. type shaped like a "T"...couldn't find much online...started another thread on that).

  9. #9
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Captain Ron View Post
    Thanks Guys! I did have lots of fuel (1/4 in the right tank, >3/4 in the left tank, left tank selected for landing). I also thought maybe the tank vents were obstructed but I could easily blow though the caps and had lots of fuel flow at the fuel bowl with the drain open.

    I like the idea of the primer leaking/failing since it is a common link between the symptoms. What's the easiest way to check if it is leaking? Remove it and pressurize with air or try to pump some fuel from a jar or what? Need to figure out how to disassemble the thing (old Imperial Brass Co. type shaped like a "T"...couldn't find much online...started another thread on that).
    You’d know if a cap vent was plugged. The tank would collapse


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  10. #10
    algonquin's Avatar
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    OK Cpt. R, take a small step back your getting close to the jaws of the trap. Don't talk yourself into knowing what's wrong before you find the problem. I don't know the laws in Canada so all I can say is your getting into areas that require A&P's if you don't need to meet that requirement OK. You might take a primer line off the cyl. Have someone pump the primer andcatch the fuel in a cup. Put it back on and do the same on the other side. Or all the primer lines. Compare the amount of fuel in each. Now no problem, check the main primer line , hang a cup on it and see if it's weeping fuel. Also you can put a vac. Pump on it and see if it closes off when locked . Then you will know if the primer works or not. Just jumping into the rebuild may lead you to believe you found the problem and then you may find at 300' on take off that you didn't. Again you will solve this just stay focused!
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  11. #11
    Steve Pierce's Avatar
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    You could cap off the primer system to troubleshoot. The primer usually consists of a few o'rings and some check balls and springs. I can't imagine the extra fuel from a leaking primer causing an engine to flood out and quit. My experience with hard starting engines has been related to magnetos where the internal timing has drifter over time. Have had a stopped up fuel vent that you could here a pop when the pressure relieved itself and the tank goes back into shape or the air rushing in when the cap is removed. I think I would start by looking at the spark plugs and checking compression while you are there. Plugs are good indicators of what might be going on.
    Steve Pierce

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  12. #12
    hotrod180's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    .....My experience with hard starting engines has been related to magnetos where the internal timing has drifter over time...... I think I would start by looking at the spark plugs and checking compression while you are there. Plugs are good indicators of what might be going on.
    I've had starting issues that I thought were magneto related but actually turned out to be the plugs.

    https://www.aircraftmagnetoservice.net/magneto-troubleshooting-guide
    Cessna Skywagon-- accept no substitute!

  13. #13
    Captain Ron's Avatar
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    Thanks again guys!

    I've started a flow-chart/checklist to go through when I have a day available to troubleshoot as Algonquin suggested. As he said, easy to get fixated on one thing and think you've got it and get a nasty surprise later. Particularly with intermittent faults or ones you can't replicate. In this case I'm not totally convinced the primer is the culprit for the engine quitting but it definitely isn't pumping fuel reliably so that is something to address regardless. I'll post an update if/when I discover something.

    BTW - I think this is something you'd need an A&P for ("AME" here in Canada) but the airplane is E-AB so it is legal for the owner to complete the work. That of course doesn't mean able or safe to complete the work so need to be honest with yourself regarding skills. I'd like to think changing some o-rings in a 1940's era primer would qualify for owner/pilot permitted maintenance but I've largely given up looking for logic with FAA/TC.
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    The last time that happened to me (with 0470-50) I changed the carburetor and that fixed it. It didn't like the throttle closed with the engine still spinning down. I'd have to catch it with throttle if it got too slow. I did know the the ignition and basic engine condition were good though... I agree with Steve, if you think it might be the primer then cap it..
    It's a shotgun approach and not the same engine but might have some similarity..
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  15. #15
    skywagon8a's Avatar
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    One thing to add to your list is to flush out the carburetor. With the fuel valve on, pull the drain plug on the back of the carb bowl and let some gas wash through. This will flush out any contaminates and water droplets which may be residing in the bowl. I'm not suggesting that this is the answer only that it eliminates one possibility.

    Quitting on landing could be as simple as the idle rpm adjustment is too low and/or the idle mixture is too lean.

    A weak spark from the mags could contribute to hard starting and poor idling. This could be corrected by resetting the points for a strong spark E-gap and making sure that the timing to the engine is correct. A strong spark E-gap is not necessarily the same as what the manual says that the point setting should be.
    N1PA
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  16. #16
    Captain Ron's Avatar
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    46 Cub - "The last time that happened to me (with 0470-50) I changed the carburetor and that fixed it." - Do you know what was wrong with the carb?

  17. #17
    BC12D-4-85's Avatar
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    Did you later check the rpm rise at mixture cutoff? Try with throttle closed then in 100 rpm increments to about 1400. There's a series of bleed holes that feed during low speed until the main jet nozzle takes over. See this link for troubleshooting.

    http://www.insightavionics.com/pdf%2...b%20Manual.pdf

    Gary
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  18. #18
    Captain Ron's Avatar
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    Gary - Regrettably I've not been able to do any serious troubleshooting yet on account of my work schedule and I forgot to look when I shut it down the day of. That's near the top of my to do list. Thanks for the tip about trying from different speeds.
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  19. #19
    BC12D-4-85's Avatar
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    The different speeds and cutoff rise were asked of me years ago by an old time mechanic. As the carb transitions from idle to main jet flow it can help diagnose if fuel flow is ok. That's all I did and gave him the info. He drained the carb bowl, accelerator pump sump, cleaned the inlet filter screen and set the float level plus some gaskets. The idle passages were plugged some and float needle was worn. My primer was also leaking when shutoff (he disconnected it to test) so he put in new seals and fussed with it and then off I went.

    Gary
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  20. #20

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    Quote Originally Posted by Captain Ron View Post
    46 Cub - "The last time that happened to me (with 0470-50) I changed the carburetor and that fixed it." - Do you know what was wrong with the carb?
    Hi Ron,
    No, sorry but I didn't look into it any further..
    Jose
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