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Fuel system setup

Old 12-19-2011, 11:12 AM
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acdii
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Default Fuel system setup

Still building my P-51 with DLE20. I have a Dubro tank and gas plug, I also have one of those quick filler valves. I have the fuel lines and hose barbs, and the spring clamps to keep the fuel line attached, but not sure how to connect it all. The filter clunk line goes to the carb same as glow? THe fuel filler though has an outlet that says to engine.

What is the correct setup for this so I dont have gas leaking all over the place and a crappy feeding fuel system. The only one I setup was 20 years ago with a piper cub, fuel line for vent, one for pressure off the exhaust, and one to the carb, the carb line was also used for filling. At least that was how I remembered it.
Old 12-19-2011, 12:06 PM
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BadAzzMaxx
 
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Default RE: Fuel system setup

First you do not run the vent line to the muffler, Just rout it to the bottom of the plane.

I like to use a three line system, One line for the vent, one separate line for the carb and a third line to fill and remove fuel.

That way you do not have get the fuel back to the carb every time you fuel the tank like with a two line system with a T for fueling.

Milton
Old 12-19-2011, 12:46 PM
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arobatx
 
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Default RE: Fuel system setup

+1 on Maxx's post.... and I would recommend not using the filler valve at all. It only opens up an additional place for leaks. Keep it simple, and straight forward and you will be glad you did later.
Old 12-19-2011, 02:41 PM
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aussiesteve
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Default RE: Fuel system setup

+ 2 on Miltons Post

The only thing that should be between your clunk outlet your carb inlet is tygon (or Viton or similar such fuel tubing). No filter, no Tee piece, no nothing. Use a Walbro Felt clunk (available from any saw shop) and filter your fuel before it goes into your plane.

Use a seperate line for your filler. The tube in the stopper for the filler should bend and go close to the bottom of the fuel tank (no need for 2 clunks in the tank). This way it can be used to empty the tank (no need to completely empty a gasser tank - in fact it is beneficial to leave alittle fuel in there)

The Vent line should go to above the top of the tank then exit the fuselage below it. Some like to take it to behind the tank also but it is not really necessary (even though I do it that way most of the time).

Old 12-19-2011, 03:23 PM
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av8tor1977
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Default RE: Fuel system setup

Well, I have to admit I don't understand a fuel system set up that particular way. Where does the air go in the tank when it is displaced by fuel when you are fueling the airplane??

I use and recommend a three line system, though I used a two line with no problems for years... However, with the two line system I had a "T" in the line going to the carb for fueling, and of course the vent displaced the air while this was done.

AV8TOR
Old 12-19-2011, 07:11 PM
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captinjohn
 
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Default RE: Fuel system setup

The only thing that should be between your clunk outlet your carb inlet is tygon (or Viton or similar such fuel tubing). No filter, no Tee piece, no nothing. Use a Walbro Felt clunk (available from any saw shop) and filter your fuel before it goes into your plane.

Use a seperate line for your filler. The tube in the stopper for the filler should bend and go close to the bottom of the fuel tank (no need for 2 clunks in the tank). This way it can be used to empty the tank (no need to completely empty a gasser tank - in fact it is beneficial to leave alittle fuel in there)= Posted by Steve.

Thevent line should go to above thetop of the tank thenexit the fuselage below it. Some like to take it to behind the tank also but it is not really necessary (even though I do it that way most of the time).
<hr /> av8tor, The air goes out the vent.
Old 12-19-2011, 08:29 PM
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aussiesteve
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Default RE: Fuel system setup

Ok, probably didn't explain it quite well enough.

3 Lines go through the tank

Line 1 - "Clunk line".
On the inside of the tank is a Felt Clunk (very low price from the local saw shop), attached to a piece of flexible gas safe line (Tygon, Viton or similar such material - NEVER silicon Glow fuel tubing). On the outside is a line going directly to the carb.

Line 2 - "Fill Line"
On the inside of the tank this line goes to the bottom of the tank. (When using a Dubro style stopper as listed in the OP, I use a solid piece of metal tubing with a 90 degree bend for this). On the outside of the tank is a flexible fuel line that goes to the Fuel dot (or in the case listed by the OP, the fueller valve). Some like to have a filter in this line, I have never found it necessary.

Line 3 - "Vent Line"
On the inside of the tank is a line that goes to the top of the tank. (When using a Dubro style stopper as listed in the OP, I use a solid piece of metal tubing with about a 45 degree bend for this and with a small piece of flexible line on the end - usually cut with a "V" on the end - it sits right at the top of the tank). On the outside of the tank, is a flexible line that goes above the eank then exits below the tank through the fuselage. (I usually glue on a piece of balsa at the bottom of the firewall and run the end of the vent through that to hold it in place.)

On my fuel filler tank, I filter the fuel going into it through a fine filter and I have a paper filter on the outlet of the filler pump to ensure the fuel going into the plane is clean. The felt clunk takes care of anything that may get past this.

I don't add anything to the line from the clunk to the carb as I have seen too many problems over the years where tee's etc in this line have caused air leaks. (The gasser carbs have a pretty effective pump in them and if there is a pinhole to be found, they will find it and suck air through it even if it isn't large enough for fuel to leak out).

I will try to find some photos of one later if nobody else manages to post it before then.
Old 12-19-2011, 10:16 PM
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av8tor1977
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Default RE: Fuel system setup

You're absolutely right Steve. I misread your post. Sorry. []

AV8TOR
Old 12-20-2011, 06:04 AM
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acdii
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Default RE: Fuel system setup

Thanks Steve, that clears it up, and thinking back that is how I had it setup on my plane 20 years ago, but my mind just couldn't remember the details.  I have a filter clunk, kinda looks like what is uses in a fish tank as a bubbler.

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