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Thread: Engine woes

  1. #1

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    Engine woes

    Have a supercub that I just restored for a guy and I'm having trouble getting the engine running right. O-320-A2B widedeck with a 74/60 prop, 190 smoh that is running way to rich, was a dog on take off but just thought it was the prop. Very shaky and only getting 2300 on climb out, next time I flew it took it for a Cruze and lean the engine out and gained over 200rpm and smoothed right out. Called my engine guru and he said was the carb, probably had stuck float or something of that nature. Changed the carb out for another one sitting in the shop and no change runs like sh!t full rich but great with the mixture pulled 1/2 way out. Can't be 2 bad carbs so I took the carb off my cub and put it on, it's a little better but still not running right, now I only get 75/100 rpm increase when I lean but still runs ruff and will not smooth out no matter how much I lean, I'm plum out of ideas anyone have a clue?

    chuck
    Last edited by PA-22/20-160; 08-03-2018 at 10:41 PM.

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    Restricted exhaust?
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    Just did the muffler AD and inspected it, didn't see anything and it's making full power once it's leaned so I don't think that's it but did cross my mind.

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    BC12D-4-85's Avatar
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    Primer leaking? Carb heat box ok? Air filter ok?

    Gary
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  5. #5

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    No primer hooked up, used 2 diffrent air boxes and carb heat works as it should. New paper air filter on one and a bracket air filter on the other.
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  6. #6
    aktango58's Avatar
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    could it simply be that you are in HOT weather and high density altitude, and your carbs are all set to operate in the dead of winter?

    If the carbs are set for super cold weather, hot weather will make them run very rich.
    I don't know where you've been me lad, but I see you won first Prize!
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  7. #7
    BC12D-4-85's Avatar
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    Good fuel? Muffler and plugs read sooty?

    Put the owner's carb on yours and fly it - same problem? See if the problem goes with the carb or if it's the engine or fuel in his plane.

    Gary
    Last edited by BC12D-4-85; 08-03-2018 at 11:20 PM.

  8. #8
    www.SkupTech.com mike mcs repair's Avatar
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    Engine woes

    Stuck valve/ bent push rod?(on exhaust valve )


    Sent from my iPhone using SuperCub.Org

  9. #9
    BC12D-4-85's Avatar
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    O-320 with 74/60 isn't going to wind up as much as a 56-52. Lots of throttle to get to climb 2300 and loading the engine as a result. Lots of throttle can produce rich mixture and ok to cool engine. If there's an economizer circuit that's no longer in the mix it can do that - not sure if it's installed on his carb tho. Plus accelerator pump discharge check valve can leak and add fuel.

    Move the carb and see if the problem goes with it. As Mike notes check valve/cam action per cylinder and mag timing correct. Marvel oil can help.

    Density altitude is another hot and high problem as noted earlier.

    Muffler outlet open and not partially blocked with heater cone on the bail?

    Carb reading material. There's an interesting section on troubleshooting included: http://www.insightavionics.com/pdf%2...b%20Manual.pdf

    Gary
    Last edited by BC12D-4-85; 08-04-2018 at 12:37 PM.
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  10. #10
    PerryB's Avatar
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    Gary's right about the prop. That's a lot of prop for that engine. Can you borrow a 52 pitch, or better yet a Borer? An 82-41/42 would answer that question quickly.
    After Monday and Tuesday, even the calendar says WTF !

  11. #11
    n40ff's Avatar
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    While a 74X60 is relatively course pitch it's not really too much and has nothing to do with mixture, something else is going on.

    TCDS(PA22) says min. static with a Sen. 74DM is 2250 rpm/ max. 2450 rpm doesn't mention pitch.

    Just for reference, I ran a 74X58 on my Acroduster 2 with IO320-160. I got 2300 rpm static and 2500 rpm in a 100 mph climb full rich. My carb. was slightly rich and I could lean to get almost 2600 rpm in the 100 IAS climb.


    Jack
    Last edited by n40ff; 08-04-2018 at 07:10 AM.

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    So far I've had 3 diffrent -32 carbs on and 2 diffrent airboxes and filters, has no primer system, check muffler, mag timing all looks good. Density altitude was under 2000 feet when I was flying last night so not real hot and I'm only at 900 feet. Thinking back the plane did this before I recovered it, I flew it home from Montana and noticed it started running crappy when the mixer was pushed in and it was in the 50's then I just didn't think much of it at the time.

    Thinking valve/lifter problem but wouldn't it run crappy all the time? leaned this engine runs just like every O-320 I've flown behind.

  13. #13
    skywagon8a's Avatar
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    First of all that prop is wrong. A standard prop for a 150 hp PA-18 is 7456. In order to get the rpms that you are asking of it your throttle setting is too far forward (high manifold pressure). This would tend to force the engine to run excessively rich. I'm thinking that you have a Tripacer prop with a Super Cub carburetor with all the wrong internal jetting. To get Super Cub performance change the prop.
    N1PA
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    cubpilot2's Avatar
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    Quote Originally Posted by skywagon8a View Post
    First of all that prop is wrong. A standard prop for a 150 hp PA-18 is 7456. In order to get the rpms that you are asking of it your throttle setting is too far forward (high manifold pressure). This would tend to force the engine to run excessively rich. I'm thinking that you have a Tripacer prop with a Super Cub carburetor with all the wrong internal jetting. To get Super Cub performance change the prop.

    i guess I not totally following the logic on this. I thought carbs are jetted for the hp not the prop pitch it’s pulling. Their both 150 hp. Leaning cured /improved his problem.

    That prop or ones of similar in pitch are used on some Cherokee 140s. It would normally be sluggish in performance on a cub but if you want to go “fast”.

    Chuck
    you didnt mention the ignition system condition. This may be a stretch; but you may have a week ignition which could be compensated for with leaning. Double check the timing etc.

    interesting problem
    good luck
    Last edited by cubpilot2; 08-04-2018 at 10:12 PM.
    Ed

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    Are you getting good mag checks on runup? maybe you have a plug or two that isn't up to the task at high power settings and are misfiring.
    It's been mentioned before, but how fresh is the fuel.....

  16. #16
    txpacer's Avatar
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    I had that happen with exactly the same indications. It turned out that the timing gear in the accessory case was marked one tooth off. Pull the plugs and rocker covers and check if your valves are moving at the right time.

    Edit: Just noticed that it already had 190 hours on the engine, so maybe not.
    Last edited by txpacer; 08-04-2018 at 11:55 AM.
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  17. #17
    skywagon8a's Avatar
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    Quote Originally Posted by cubpilot2 View Post
    i guess I not totally following the logic on this. I thought carbs are jetted for the hp not the prop pitch it’s pulling. Their both 150 hp. Leaning cured /improved his problem.

    That prop or ones of similar in pitch are used on some Cherokee 140s. It would normally be sluggish in performance on a cub but if you want to go “fast”.
    That was strictly off the top of my head without any research. I just checked and found the Cub and the Tripacer use the same carbs. So the carb would not be the issue unless all three had the same over rich issue.
    N1PA

  18. #18

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    Do a mag check when you are flying at 2400 rpm. Sounds like a fuel issue to me, however you have beat that horse pretty hard.
    DENNY

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    PerryB's Avatar
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    Chuck, what kind of DA are you operating at? That's going to have a huge impact on your air/fuel ratio, especially at full throttle. I still think you're way overpitched. For a bone stock Cub with small tires, 56 is about the limit of what you'd want to run. For anyone doing typical Cub stuff, 52 is going to perform a LOT better on a 150.
    After Monday and Tuesday, even the calendar says WTF !

  20. #20

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    Quote Originally Posted by PerryB View Post
    Chuck, what kind of DA are you operating at? That's going to have a huge impact on your air/fuel ratio, especially at full throttle. I still think you're way overpitched. For a bone stock Cub with small tires, 56 is about the limit of what you'd want to run. For anyone doing typical Cub stuff, 52 is going to perform a LOT better on a 150.
    DA is under 2000' so I wouldn't think it would be a problem but who knows at this point.

  21. #21

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    One other thing is the engine was dieseling at shut down from time to time.

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    Quote Originally Posted by txpacer View Post
    I had that happen with exactly the same indications. It turned out that the timing gear in the accessory case was marked one tooth off. Pull the plugs and rocker covers and check if your valves are moving at the right time.

    Edit: Just noticed that it already had 190 hours on the engine, so maybe not.
    Your engine ran fine if you leaned it? This might be a possibility as you can make it run right and the previous owner maybe just dealt with it.

  23. #23
    BC12D-4-85's Avatar
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    Quote Originally Posted by PA-22/20-160 View Post
    One other thing is the engine was dieseling at shut down from time to time.
    Can't run much if the mixture metering valve fully shuts off fuel flow to the main and idle circuits unless some other carb circuit is still supplying fuel...like the accelerator pump discharge tube via a leaking check valve. See the troubleshooting charts: http://www.insightavionics.com/pdf%2...b%20Manual.pdf

    I suppose if real rich some fuel and engine oil can pool in the intake and cylinders and offer fuel for dieseling after lean out.

    Gary

  24. #24
    skywagon8a's Avatar
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    Quote Originally Posted by PA-22/20-160 View Post
    One other thing is the engine was dieseling at shut down from time to time.
    This can happen when the mixture is pulled to idle cutoff with the engine running at idle and the ignition is too far advanced or only with one impulse coupling which keeps the other mag running an advanced spark.
    N1PA

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    Double checked the static RPM and is a little over 2300, did another mag check and nice smooth 150 rpm drop engine will idle fine on one mag. Will double check the timing and going to wait until I have a nice cool morning to go fly and see what it dose. May throw my borer prop on just as an experiment. Also had another look up the tail pipe and looks clear.

  26. #26
    n40ff's Avatar
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    PA18 TCDS

    (a) Propeller - Sensenich M74DM or 74DM6 fixed pitch metal (landplane and seaplane) +30 lb. (-57) Static r.p.m. at maximum permissible throttle setting: Not over 2450 r.p.m., not under 2350 r.p.m. Not over 2550 r.p.m., not under 2450 r.p.m. when operating as a Glider or Banner Tow. No additional tolerance permitted. Diameter: Not over 74 in., not under 72.5 in.


    Again like the PA22 I quoted before it doesn't mention pitch. I agree that the 74X60 is too much and a 56 would be better.

    Fact is if static is under 2350 you are not legal. Of coarse tach calibration is issue but whatever 60" pitch probably shouldn't be on a PA18.

    Jack

  27. #27
    cubpilot2's Avatar
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    Quote Originally Posted by PA-22/20-160 View Post
    Double checked the static RPM and is a little over 2300, did another mag check and nice smooth 150 rpm drop engine will idle fine on one mag. Will double check the timing and going to wait until I have a nice cool morning to go fly and see what it dose. May throw my borer prop on just as an experiment. Also had another look up the tail pipe and looks clear.
    I’m guessing ignition is a bit week or too far advanced. If it’s solid you should expect 100 rpm drops or less. I think the dieseling symptom is a clue.
    Ed

  28. #28
    behindpropellers's Avatar
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    How long ago was the 190 smoh?

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    PerryB's Avatar
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    Quote Originally Posted by cubpilot2 View Post
    I’m guessing ignition is a bit week or too far advanced. If it’s solid you should expect 100 rpm drops or less. I think the dieseling symptom is a clue.
    You and Skywagon8A have both mentioned ignition anomalies (advanced timing being your common thread) as causes of dieseling. I'd like some elaboration on that because I simply can't connect those dots. If there is no fuel (idle cut-off) it's not going to pop, sputter or fart. It sounds to me like it's getting an external source of fuel, like maybe it's sucking it through the primer. The rich condition would also load the plugs with lead and carbon, and they'd be prone to glow-plugging. A leaking primer would also explain why swapping carbs has little to no effect on the rich condition.
    After Monday and Tuesday, even the calendar says WTF !
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  30. #30
    BC12D-4-85's Avatar
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    I'd pull the plugs and have a look for unburned fuel and oil. Weak spark or improper timing maybe not combusting the residuals especially at shutdown = dieseling. Maybe not start so good either until the rpms build? He did mention earlier that no primer was installed so there goes that usual suspect. It can suck some fuel through the accelerator discharge if that valve is weak. See the troubleshooting link for a test.

    Again, is the fuel good and not old or contaminated with something? Smell it and let some dry on a surface and see if it leaves an oily residue. And compression. It takes lots for the engine to run ok.

    Simple dish: Fuel, compression, and ignition.

    Gary
    Last edited by BC12D-4-85; 08-04-2018 at 11:57 PM.

  31. #31
    PerryB's Avatar
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    I guess I blew it on the primer theory then. And it sounded so good. I'll go sit in the corner now.
    After Monday and Tuesday, even the calendar says WTF !

  32. #32
    BC12D-4-85's Avatar
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    Quote Originally Posted by PerryB View Post
    I guess I blew it on the primer theory then. And it sounded so good. I'll go sit in the corner now.
    No need for that self-abuse. It's all good and interesting, but without the right ingredients mixed in the proper proportions at the right time these simple engines can frustrate. I hope Chuck doesn't get discouraged and has the time and compensation to fix it. I think he'll get to the center of the onion soon.

    Edit: Ooops! I forgot to add air to the simple engine dish recipe above. Can I join you in the corner writing "I'll not FU much" on the wall?

    Gary
    Last edited by BC12D-4-85; 08-05-2018 at 01:21 AM.

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    Since it was right after overhaul I'm gonna guess valve lash too tight, and intakes pushing air back and forth. Or improperly seating valves, but a compression test would have already eliminated that possibility..
    If it was just an idle-shutdown thing I would say too rich and too slow an idle. Easy to test by speeding up and leaning before final shutdown.
    For the "glow plug" question, you can test that by just shutting the mags off.. If it runs on it's not the mags...
    I'm ready to join 12D and Perry in the corner... If Perry hadn't already been shot down I'd have been in the primer camp too!
    I don't want anyone to be alone in the FU department...

  34. #34
    BC12D-4-85's Avatar
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    Hmmmm...46 Cub, Perry and me with only two walls to write our don't do its on. Ok, I'll take the floor and let you guys write on the walls.

    Hope Chuck the OP gets the courage to fix it before it goes viral.

    Gary

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    Glutton for punishment...
    No rags in the intake or such?
    I had a friend who had huge trouble starting a factory reman on his cub... we had all kinds of advice... lean this, pump that..
    Turns out the plastic plug was still in the plenum where the carb bolts on.. It ran like a dream once he found that!

  36. #36
    BC12D-4-85's Avatar
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    Here's a 1966 song from Charley Pride (https://www.youtube.com/watch?v=S_O0rRsnfNs) "Oh the mice crawl at night that's what they say, when the Sun goes down then the mice will play." Put stuff in the intake and whatever.

    Gary

  37. #37
    skywagon8a's Avatar
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    Quote Originally Posted by PA-22/20-160 View Post
    Double checked the static RPM and is a little over 2300, did another mag check and nice smooth 150 rpm drop engine will idle fine on one mag. Will double check the timing and going to wait until I have a nice cool morning to go fly and see what it dose. May throw my borer prop on just as an experiment. Also had another look up the tail pipe and looks clear.
    There is a major big clue. Ding, Ding, Ding! When the mag check is as high as 100 rpm drop it is time to 1/ check the timing to the engine and if OK it is 2/ Pull the mag and check Egap. At 150 drop and smooth your plugs and harness are OK. The mag drop should be up to 50 rpm with 100 rpm being the high limit. Do you know and understand what Egap is? Learn about it if you don't. Then fix those mags. Don't send them out. It is only a five minute job which can be done with a screwdriver and a piece of paper. I've gone over this in the past in other postings. The mag manufacturers manuals give you instructions which are safe and get you close. However if you understand Egap you can get it closer.

    Now if what I've described above proves to be not correct, I would suspect the gears in the engine being improperly engaged as txpacer mentions in post #16. It could be just the gear on the mag being 180 degrees off. This would have been covered up by someone monkeying with the mag timing.

    Quote Originally Posted by PerryB View Post
    You and Skywagon8A have both mentioned ignition anomalies (advanced timing being your common thread) as causes of dieseling. I'd like some elaboration on that because I simply can't connect those dots. If there is no fuel (idle cut-off) it's not going to pop, sputter or fart. It sounds to me like it's getting an external source of fuel, like maybe it's sucking it through the primer. The rich condition would also load the plugs with lead and carbon, and they'd be prone to glow-plugging. A leaking primer would also explain why swapping carbs has little to no effect on the rich condition.
    Perry, It has been called dieseling. It may not be that. The 0-360 has this tendency when shut down at idle rpm speeds. That seems to be incomplete burning of the residual fuel which is ignited by the advanced spark from the non-impulse mag causing a mild kickback. If you run the 0-360 at just a little over 1000 rpm, pull the mixture to idle cutoff then immediately when the engine stops firing close and hold the throttle until the engine stops turning, the shaking "dieseling" will disappear. I attributed this to advanced timing on the non-impulse mag because of my experience with my Cub. It has two Pmags which change their timing due to the Pmag's ability to determine the firing requirements of the engine. As a result when at idle rpm the timing is retarded. My IO-360 will stop at idle rpm by pulling the mixture with absolutely no evidence of "dieseling" what so ever.
    N1PA
    Thanks PerryB thanked for this post

  38. #38

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    Quote Originally Posted by PerryB View Post
    You and Skywagon8A have both mentioned ignition anomalies (advanced timing being your common thread) as causes of dieseling. I'd like some elaboration on that because I simply can't connect those dots. If there is no fuel (idle cut-off) it's not going to pop, sputter or fart. It sounds to me like it's getting an external source of fuel, like maybe it's sucking it through the primer. The rich condition would also load the plugs with lead and carbon, and they'd be prone to glow-plugging. A leaking primer would also explain why swapping carbs has little to no effect on the rich condition.
    Leaking primer would explain the problem but it doesn't have a primer hooked up.

  39. #39
    skywagon8a's Avatar
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    Leaking primer would not have anything to do with a smooth 150 rpm mag drop.
    N1PA

  40. #40
    skywagon8a's Avatar
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    Quote Originally Posted by n40ff View Post
    PA18 TCDS

    (a) Propeller - Sensenich M74DM or 74DM6 fixed pitch metal (landplane and seaplane) +30 lb. (-57) Static r.p.m. at maximum permissible throttle setting: Not over 2450 r.p.m., not under 2350 r.p.m. Not over 2550 r.p.m., not under 2450 r.p.m. when operating as a Glider or Banner Tow. No additional tolerance permitted. Diameter: Not over 74 in., not under 72.5 in.


    Again like the PA22 I quoted before it doesn't mention pitch. I agree that the 74X60 is too much and a 56 would be better.

    Fact is if static is under 2350 you are not legal. Of coarse tach calibration is issue but whatever 60" pitch probably shouldn't be on a PA18.

    Jack
    From Sensenich:
    http://www.sensenich.com/wp-content/...1349891787.pdf
    Piper PA-18 Super Cub 150 Lycoming O-320/ 150 (standard)= 74DM6-0-56, (climb)= 74DM6-0-54, (cruise)= 74DM6-0-58 The numbers in red are the pitch in inches.
    N1PA

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