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How far will a gas engine draw fuel?

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Old 02-22-2014, 04:26 PM
  #1
gregandhollie
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Default 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?
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Old 02-22-2014, 04:33 PM
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If the pump is working right it will draw 3 feet straight up.

Milton
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Old 02-22-2014, 06:20 PM
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Careful will filling valves, some have a tendency to leak.
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Old 02-22-2014, 06:46 PM
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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.
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Old 02-22-2014, 06:49 PM
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On my test stand (break-in stand) the fuel can is three feet below the engine.
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Old 02-22-2014, 07:46 PM
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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.
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Old 02-22-2014, 08:05 PM
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+1 for all posts so far.

AV8TOR
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Old 02-22-2014, 08:24 PM
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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
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Old 02-23-2014, 05:16 AM
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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,
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Old 02-23-2014, 08:05 AM
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+1 for the three line tank with a fuel dot.
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Old 02-23-2014, 04:18 PM
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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
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Old 02-24-2014, 08:41 AM
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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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Old 02-24-2014, 10:57 AM
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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 10:59 AM.
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Old 02-24-2014, 06:55 PM
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What is a three line set up? How about a diagram!!!
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Old 02-25-2014, 12:23 AM
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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.
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