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Thread: Stromberg carb

  1. #1
    Charlie Longley's Avatar
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    Stromberg carb

    I need a little help on a Stromberg carb. The J-3 I changed the spar on sat for 4 months with the gas turned off. I tried to start it today. I about wore my arm out propping it! The owner says he typically pulls the engine through 10 blades with the fuel on. Usually around the 7th blade there’s fuel dripping out of the carb. I pulled it through 20 blades 2-3 times and no fuel is dripping out. I disconnected the fuel line from the carb and turned the gas on. There was good flow. I than pulled the screen on the side of the carb it was good as well.

    I am thinking a stuck float. Does anyone have experience with this? My arm thanks you in advance!

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    Last edited by Charlie Longley; 03-26-2020 at 09:43 PM.

  2. #2
    BC12D-4-85's Avatar
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    No expert-former owner. If I suspect something stuck use a rubber hammer or ? and gently tap where it won't crack easily. Mine would suck fuel best at idle. If the throttle was opened it had less vacuum or whatever pulls fuel into the bore. Fixed with Marvel carb and $,$$$.

    Gary
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  3. #3
    Charlie Longley's Avatar
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    Quote Originally Posted by BC12D-4-85 View Post
    No expert-former owner. If I suspect something stuck use a rubber hammer or ? and gently tap where it won't crack easily. Mine would suck fuel best at idle. If the throttle was opened it had less vacuum or whatever pulls fuel into the bore. Fixed with Marvel carb and $,$$$.

    Gary
    Guess I should’ve said I whacked the crap out of it with my heaviest plastic handle screwdriver and dead blow hammer.

  4. #4
    BC12D-4-85's Avatar
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    Time to call a Doctor: http://thestrombergspecialist.com/index.php and http://thestrombergspecialist.com/in...fo/newsletters and http://thestrombergspecialist.com/in...articles-links

    Edit: How about draining the carb bowl then letting it refill? If it refills and doesn't overfill the float must be working.

    Gary
    Last edited by BC12D-4-85; 03-26-2020 at 10:36 PM.
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  5. #5
    cubdriver2's Avatar
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    The throttle needs to be totally closed to pull fuel, even cracked a 1/16" and it will not start cold

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  6. #6
    Charlie Longley's Avatar
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    Well I got the J-3 running. Turned out the carb was fine. I pulled it off and split it open. Whoever overhauled it last did a nice job! It was very clean. I checked the compressions and they were all low except the one cylinder that was just overhauled. I theorized the engine didn't have enough compression to pull the fuel up through the carb. The primer wasn't working well/at all. I pulled it apart and tried to repair it with no luck. I ended up getting an ACS primer from Spruce. Irritated me that it wasn't bolt in! I had to stop by Grainger and get some compression fittings. Anyway got the primer in and was able to fire up the engine this morning. Checked the compressions afterword and they were all above 78. (The airplane had sat for 4 months.)

    On a side note I talked to the Stromberg Guru Bob. Nice enough old guy but all he wanted to do is tell me about his health problems and have me send the carb in for overhaul. I just looked at his website and he's not accepting carbs at this time. It's a very simple carb with like 3 gaskets and one moving part. Should be fairly easy to overhaul with parts from Spruce.
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  7. #7

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    Or you could just clean it once in a while. These things are extremely reliable and dirt-simple. Sure sounds like your throttle wasn't closed all the way - you should hear a juicy sound when you pull it through.
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  8. #8
    JP's Avatar
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    Fresno Air Parts sells reasonably priced overhaul kits (gaskets and needle/seat). Sometimes the needle notch gets worn with use and will hang up; tapping on the side of the carb will free it up. Better to replace it as sometimes it will get hung up at inopportune moments. Really a simple carb. Easy to overhaul and set up properly. Just check the brass float for leaks by dunking in gas....
    JP Russell--The Cub Therapist
    1947 PA-11 Cub Special
    www.bloomerrussellbeaupain.com
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  9. #9

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    Oh, yeah - that needle slot. I had one with machine marks from manufacture that would hang up the float. Polished it up, and have several thousand successful hours behind it.

    I made a simple wood stand with a way to dump the carb contents into an elevated can with a valve. I recommend at least ten trials after setting up the float, to make sure it always shuts off at the same spot.

    The idle circuits are trivially simple - just remember, all holes were drilled in a straight line, then plugged. Force carb cleaner through both idle circuits, the air bleed, and the main jet. Then all will be well.
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  10. #10

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    If you might have an original neoprene tipped needle, and if you might have the seat for the stainless needle, and if you got a little alcohol in the gas, the neoprene tip can swell and stick in the seat.
    You can't get there from here. You have to go over yonder and start from there.
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  11. #11
    Charlie Longley's Avatar
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    Quote Originally Posted by bob turner View Post
    Or you could just clean it once in a while. These things are extremely reliable and dirt-simple. Sure sounds like your throttle wasn't closed all the way - you should hear a juicy sound when you pull it through.
    No I double and triple checked it after you mentioned that. The throttle was on the idle stop.

  12. #12
    BC12D-4-85's Avatar
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    I suspect the combo of the noted lower than normal compression and/or induction leaks made self-priming difficult. Even with a MS carb on a low time C-90-8 I had recurring problems starting at +30F or lower engine temps. It would take a warmer (and maybe a bit tighter?) engine to fire off. With the almost new MS carb, dual impulse coupled Bendix mags, clean plugs, induction spider primer (later replaced with direct to cylinder priming) it would refuse to start via hand propping at those temps. I think my personal record was somewhere around 45 minutes of propping 20 times, followed by reverse propping thinking it was too rich, then another repeat. It would pop on one cylinder then die. Idle mixture was set to +50 rpm at idle cutoff so that wasn't a too lean situation.

    The easy fix for me was heat but sometimes during a fall snowstorm parked on floats a mile from camp I was reluctant to trek back for a heater. I finally had all four cylinders primed and that minimized the issue. There was simply too much cold metal between the carb and spark plugs condensing fuel for it to start reliably.

    Gary

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