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Thread: fuel injected engine fuel return lines

  1. #1

    fuel injected engine fuel return lines

    Whats the rule on fuel return lines for injected engines? Do need a line to both tanks? If you have a header tank in addition to the wing tanks can the return line go there? Maybe not if there isn't room for return fuel. Another reason for additional access plates to the outboard side of the wing tanks if the lines have to go back to the tanks. Wow, getting excited about building a Cruzer. Have to finish building the 2 1/2 car garage first!
    Dusty Miller
    Madisonville, TN

  2. #2
    Hello Dusty,

    In an installation with a header tank, the return line goes to the header tank. This is a setup used by Rotax and Viking.
    Without a header tank, you should use a duplex fuel selector, which switches the forward as well as the return lines, like this one: http://www.andair.co.uk/category/duplex-fuel-selectors/
    Each tank will then have its own return line, the unused fuel goes back into the tank from which it came from. This setup is typically used for UL-Power and AeroMomentum Engines.

    What I would try to avoid is a setup with a left / right selector, but only a single return line, as this just calls for an overflowing tank. Utilizing all the fuel from both tanks would also require some attention. I prefer to keep things simple, particularly when it come to fuel.

    Oliver
    Our Zenith builder's blog
    Mooney M20E - Flying
    Van's RV-10 - Empennage finished, will be put on hold for Zenith
    Zenith CH 750 Cruzer /w STOL gear - Tailfeathers done, working on fuselage kit

  3. #3
    Oliver, thank you for that information. The link to the valves was very helpful. I will not skimp on the fuel lines or selector valve. Dusty
    Dusty Miller
    Madisonville, TN

  4. #4
    Good info Oliver.
    I purchased a 750 STOL with ULp 350iS. It's always returning fuel to both tanks, I can select to pull fuel from both, but at lower fuel levels it's hard to know how low I am. Also must be pretty darn attentive when pulling fuel from one tank, as it's returning to both. I'm in the process at looking how to improve the situation, and have found this, and the zenith.aero forums real helpful. Most likely put in a header tank. Probably number five on list of dozens right now.
    Have a good one.

  5. #5
    Administrator ZenithOwner.com's Avatar
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    czyhook-I'm curious how your fuel system is plummed. Are you saying that there is only one return line and it splits and goes to both tanks? On my fuel system, I have a feed from each tank and a fuel selector that can select L or R tank. There are two return lines and each tank has it's own line. So if I'm feeding from the R tank, all of the return fuel goes to the R tank. Same if I switch to the L tank.
    Mark Pensenstadler
    Site Admin
    Price's Airpark, Linden, MI (9G2)
    S-10 | S-6S | RV-7 | Cherokee 160 | Zenith Cruzer

  6. #6
    Mark,
    There is one return line splitting somewhere (supposedly at the fuel selector). It returns fuel to both tanks always. Regardless of which tank is selected. That's the issue I'm having. I'm not the builder, just slowly learning, and working on improvements. Therefore I'm real interested in header tanks. Looking for different manufacturers, and install locations.

    A L/R/both/off selector from tanks into the header would be ideal. My one return line into the header, with appropriate vents (still researching/learning this).

    Or running a selector similar to yours, but I'd like to have the both option, and I haven't seen a duplex/return style selector with both as well.

  7. #7
    Administrator ZenithOwner.com's Avatar
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    that seems like a really dangerous setup. Your feeding from one tank but returning to two separate tanks. What happens if the other tank is full? All the return fuel would be dumped out the vent. Smart idea to go with a header tank!
    Mark Pensenstadler
    Site Admin
    Price's Airpark, Linden, MI (9G2)
    S-10 | S-6S | RV-7 | Cherokee 160 | Zenith Cruzer

  8. #8
    Quote Originally Posted by ZenithOwner.com View Post
    [...] Smart idea to go with a header tank!
    ...or a duplex valve as suggested above.

    ...or, as a quick but temporary fix, close off the return line to one of the two tanks, so that fuel is returned to only one of them. You would have to use the tank, to which the fuel is returned, first. Use it until it is half empty, then switch to the other tank. You'll probably have to switch between the two tanks a few times, as the tank with the return line will be filled again with the unused fuel from the return line.

    czhook, frankly, though, the setup you are describing doesn't make any sense. Please make absolutely sure that you exactly understand what you are doing, when working on the fuel system and that you are using appropriate hoses with the required diameter. Problems with the fuel system are the #1 cause of engine failures in experimental aircraft!
    Our Zenith builder's blog
    Mooney M20E - Flying
    Van's RV-10 - Empennage finished, will be put on hold for Zenith
    Zenith CH 750 Cruzer /w STOL gear - Tailfeathers done, working on fuselage kit

  9. #9
    Agreed. That's why I almost always operate out in "both". And I've yet to get the tanks below about five gallons a side.
    So yeah, I hope to install a header tank setup before next summer. Until then I leave carry around a lot of extra fuel. With it burning six GPH on average it's easy to fly three hour legs, and still have plenty of fuel left over. Thanks for all the info. I'll update when I get it in the works.

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