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Thread: Fuel smell after takeoff

  1. #1

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    Fuel smell after takeoff

    Hi
    Super Cub 160 hp on floats. I noticed this problem last summer and notified the owner. During the initial climb after takeoff there is a smell of gasoline that seems to come from the left side. Otherwise during cruise flight or approach there is no smell. Seems it smells (ie. it is leaking) only when the deck angle is relatively high. According to the owner there was a nut that needed tightening somewhere around the fuel selector and that was taken care of. During the first flight (takeoff from dolly) of this season he didn’t notice anything. The next flight was a water takeoff, the smell was back again. Any ideas?
    Rgds
    A

  2. #2
    cubpilot2's Avatar
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    Are the tanks full when this happens?
    Thinking of upper fuel gage gasket or fittings.
    may want to check the hoses to the gage on that side.

    If in flight and you go to a steep angle of attack do you start to smell it?
    Is it only at take off power?

    Any fuel stains (any where) ?
    Ed

  3. #3
    Steve Pierce's Avatar
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    I'd pull the wing root fairing to check the hoses at the tanks and gauges and the left side panel to check the flexible hoses there and at both the front and rear header tanks.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  4. #4
    Dave Barras's Avatar
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    I encountered this once, on a steep climb out after topping off. Its was a little
    seepage from the gas cap.
    I was relived thats all it was.

  5. #5

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    Been there done that...As Dave said, gas cap gasket(s).
    Remember, These are the Good old Days!

  6. #6

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    Check good air flow at cap....
    If you get lost while flying, don't try hail a cop. Pick up the first railroad you find and hug it until you get somewhere.

  7. #7

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    I just put the final screws back in today; test flight tomorrow. Fuel smell in cockpit, then massive leakage from inboard trailing edge (Dakota 24 gal tank, 2002 vintage.). Everybody thought/hoped it was the Curtiss drain or the fuel gauge hose. Nope - rear welded seam cracked.

    Seaplane - giant pita for me - a very old acrophobiac. I had young help lifting the tank in and out.

  8. #8
    www.SkupTech.com mike mcs repair's Avatar
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    I saw a great picture the other day where in the left side windshield channel a screw was THREADED into the 1/4" line to header tank... and they had been chasing that smell for 10 years after a rebuild....

  9. #9

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    Quote Originally Posted by mike mcs repair View Post
    I saw a great picture the other day where in the left side windshield channel a screw was THREADED into the 1/4" line to header tank... and they had been chasing that smell for 10 years after a rebuild....
    You mean like this?
    Sight tube and slider channel but equally perplexing
    E3DC11DB-62D2-4695-8D54-CDFD3BD27D2B.jpeg

  10. #10
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Oliver View Post
    You mean like this?
    Sight tube and slider channel but equally perplexing
    E3DC11DB-62D2-4695-8D54-CDFD3BD27D2B.jpeg

    no... in left window post...

  11. #11
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Oliver View Post
    You mean like this?
    Sight tube and slider channel but equally perplexing
    E3DC11DB-62D2-4695-8D54-CDFD3BD27D2B.jpeg
    no, but ALSO, i did drill into that rubber hose in 1997.... no clue till morning... and small puddle of gas in hanger i was in... hanger owner was not impressed..

  12. #12

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    So.. did you replace the hose and add an extra hose clamp?
    That’s how the previous owner solved this issue.
    same plane?��

  13. #13

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    Thanks for the suggestions! I was out flying today. Half tanks, same thing, not a strong smell but still a gas smell. Seems to be associated with a high deck angle AND full throttle.

  14. #14
    cubpilot2's Avatar
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    Could you possibly be getting exhaust fumes into the cabin; as a rich fuel mixture may smell similar.
    Just trying to connect “full power and steep angle of attack” components.
    A fuel leak won’t care what power setting your using.

    Do you have any openings under the boot cowl, or at the brake line exits that could let exhaust in?

    I guess you could test this with a CO meter....
    Ed

  15. #15

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    Do you have any openings under the boot cowl, or at the brake line exits that could let exhaust in?
    I had the same problem in my cub after installing wheel skis. In a climb, exhaust was coming through the new hydraulic line penetrations.

    RK
    Thanks JeffP thanked for this post

  16. #16
    cubpilot2's Avatar
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    Also if this could be exhaust then check your baggage door seal.
    Especially if you have one of the large ones. At higher angles the prop wash may push the fumes into that area.
    Ed

  17. #17
    spinner2's Avatar
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    I had a fuel valve with a minor leak. The gas would evaporate almost as fast as it would drip and it took a while to trace it down. But there was a lingering fuel odor often.
    "Fast is fine, but accuracy is everything." Wyatt Earp

  18. #18

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    Quote Originally Posted by cubpilot2 View Post
    Could you possibly be getting exhaust fumes into the cabin; as a rich fuel mixture may smell similar.
    Just trying to connect “full power and steep angle of attack” components.
    A fuel leak won’t care what power setting your using.

    Do you have any openings under the boot cowl, or at the brake line exits that could let exhaust in?

    I guess you could test this with a CO meter....
    Yes I think exhaust might be the culprit. There are indeed two holes underneath where the brake lines exit.... I’m not sure of other holes (not my airplane)....

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