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Thread: 912ULS vapor return line check valve

  1. #1
    Senior Member Dave S's Avatar
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    Default 912ULS vapor return line check valve

    Finally decided to install a vapor return line and found the Andair check valve frequently used was horrendously priced.

    Summit racing has a part that I decided to use instead. It is an all brass fuel system check valve with 1/4" NPT in and out. Photos attached W/part number. Delphi brands this and makes a whole lot of fuel system parts for auto and particularly racing use.

    The check valve has no internal rubber parts and is all brass with a metal spring internally. The breakout pressure of the unit is approximately 1/2 PSI according to my pressure gauge so well within what is needed for the Rotax vapor line.

    Price??? I paid $14.99 plus shipping from Summit.
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    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  2. #2

    Join Date
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    Lawrenceville, GA
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    Default Re: 912ULS vapor return line check valve

    Why is a check valve used here?
    Building a KF IV Classic

  3. #3
    Senior Member jiott's Avatar
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    Default Re: 912ULS vapor return line check valve

    The check valve is to prevent backflow thru the return line. You don't want fuel to be able to flow backwards from the fuel tanks/header tank to the carburetors when parked, in case the needle valve is leaking. You can shut of the main fuel line with the fuel on/off valve, but there is no shutoff for the return line-only the check valve.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  4. #4
    Senior Member jiott's Avatar
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    Default Re: 912ULS vapor return line check valve

    By the way, the return line should not be returning vapor. It is a fuel return line to keep cool fuel from the tanks constantly circulating in order to prevent vapor, and vapor lock, from occurring.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  5. #5

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    Sublimity , OR
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    Default Re: 912ULS vapor return line check valve

    Quote Originally Posted by jiott View Post
    By the way, the return line should not be returning vapor. It is a fuel return line to keep cool fuel from the tanks constantly circulating in order to prevent vapor, and vapor lock, from occurring.
    It's also helpful in regulating fuel pressure keeping the carb needles seated.

  6. #6
    Senior Member Dave S's Avatar
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    Default Re: 912ULS vapor return line check valve

    Jim & all,

    I stand corrected, I should not have included the term "vapor" in the original post. ( Also sorry for the misspelling of "return" on the original subject line.)

    Rotax simply calls it a return line; and, yes, it also solves the old problem of the original non bleed installations where the captive pressure between the fuel pump and carbs could rise drastically with a hot shutdown in the summer resulting in flooding of the carbs in a hot soak situation. Previously I solved this by opening the oil inspection door on the top of the cowl and letting the thing sit for 10 to 15 minutes before trying to start it again when it was really hot in the summer time. That problem used to be compounded if a person had "winter" formulated auto gas in the tanks on a really hot spring day (no need to ask how I am aware of that).

    Overall a good improvement for the engine with the orifice and return line. No more hot start embarrassment.
    Last edited by Dave S; 01-31-2022 at 02:40 PM.
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

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