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  1. #1
    gregandhollie's Avatar
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    How far will a gas engine draw fuel?

    I'm working on a CMP P-40 which I've installed an AGM 30 gas engine in. I have a 16 ounce tank about four inches aft of the engine. I'm looking at putting an inline fueling valve about six inches behind the tank, meaning fuel would leave the tank to go back to the valve and then about ten inches forward to get to the engine. Will the carb draw fuel from that far without issues or do I need to rethink my plumbing?
    www.AviationAtWar.com Share and discuss military aviation photography of yesterday and today.

  2. #2

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    If the pump is working right it will draw 3 feet straight up.

    Milton
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  3. #3
    speedracerntrixie's Avatar
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    Careful will filling valves, some have a tendency to leak.

  4. #4

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    While a Walbro carb can pull fuel quite a ways, I'm not sure it is wise to route fuel lines behind a tank just to route them forward from there to the engine. Just does not pass a reasonableness test in my book. I would try my best to locate the filler somewhere between the tank and engine.

  5. #5
    acerc's Avatar
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    On my test stand (break-in stand) the fuel can is three feet below the engine.
    Robert
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  6. #6
    earlwb's Avatar
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    I would suggest keeping the refueling and defueling line separate from the fuel line to the engine. One problem is those fueler thingies can let air leaks develop. Then the next problem is when you are refueling, the pressure of the fuel in the fuel line can overcome the fuel pump and regulator thus damaging the carb valves and or flooding the engine out.
    But otherwise as mentioned, if the carb's fuel pump is in good shape, it can draw fuel through up to three feet of fuel line.
    Club Saito #722, Sig Kadet Brotherhood #80, GlowHead Brotherhood #14,
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  7. #7
    av8tor1977's Avatar
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    +1 for all posts so far.

    AV8TOR
    If it is not SCARY, it is NO WHERE NEAR powerful enough!!
    All R/C planes have expiration dates---> It's just not printed on them anywhere!

  8. #8

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    I like useing those fuel dots. But I build my fuel tanks with 3 lines setup. Then use the fuel dot on the fill hose with the other side of the dot pluged with a small peace of hose with a bolt in it

    This way if they leak no fowl

  9. #9
    flyinwalenda's Avatar
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    I and many have experienced leaking with the fuel valves ...eventually.
    A 3-line tank works well using a fuel dot instead of a two line tank with a valve,
    Brian Ray

  10. #10
    irocbsa's Avatar
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    +1 for the three line tank with a fuel dot.

  11. #11
    TheRickster's Avatar
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    I have been using the simple two line with a "T" in the fill line for years from glow up to Gas.. I like the fact that to test the fuel system for proper operation all I have to do is hook up the fuel line and draw the fuel out. It then tests for leaks(Bubbles) and for proper clunk operation...

    Rick
    We do not do this to save money, we save money to do this..

  12. #12
    pilotpete2's Avatar
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    +2!
    The three line setup reduces the possible points where air can be drawn into the fuel line to the absolute minimum, and also allows you to use a felt filter clunk effectively, which you cannot do with two line setups.
    Pete
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  13. #13
    av8tor1977's Avatar
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    Quote Originally Posted by pilotpete2 View Post
    +2!
    The three line setup reduces the possible points where air can be drawn into the fuel line to the absolute minimum, and also allows you to use a felt filter clunk effectively, which you cannot do with two line setups.
    Pete
    Yes, I agree completely. I used two line setups in the past and didn't have much in the way of problems, but the 3 line setup is definitely better for the reasons just stated. All my planes are now set up with three line systems.

    One little tiny air leak in the fuel supply line can ruin your entire day.... and perhaps your airplane!

    AV8TOR
    Last edited by av8tor1977; 02-24-2014 at 11:59 AM.
    If it is not SCARY, it is NO WHERE NEAR powerful enough!!
    All R/C planes have expiration dates---> It's just not printed on them anywhere!

  14. #14

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    What is a three line set up? How about a diagram!!!

  15. #15
    3136's Avatar
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    Quote Originally Posted by Firewalkerd1 View Post
    What is a three line set up? How about a diagram!!!
    I don't have a diagram, but it's simple,

    1 line goes strait from carb (via brass pipe in gas stopper) into tank with a clunk, I prefer a heavy felt clunk.
    1 line goes to a looped vent line, loop 3 times and position at rear top of fuel tank, connection inside tank is a brass tube bent to top of tank
    1 line goes directly to a fuel dot for re-fuelling, I bend a tube as per vent line for this so I can see what's happening.
    Balsa USA Brotherhood 11


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