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Fuel system on a gasser?

Old 03-11-2006, 03:09 PM
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engine doctor
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Default Fuel system on a gasser?

Hi

Can someone tell me if the plumbing for a gas motor is different than a glow setup?
I am brand new to gas and am putting a 3W 106 into a H9 EXTRA 300S looks pretty straight forward but I can't figure out the venting, does it just go overboard or is the fitting different?

Dan
Old 03-11-2006, 04:34 PM
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Default RE: Fuel system on a gasser?

The plumbing is a little different on a gasser. Gas engines use pump-type carbs and do not need muffler pressure. Simply run one line from the tank through your fueling device and then to the carb. Run the vent line out the bottom of the plane. Don't worry about gas leaking out the vent. It won't.

Dr.1
Old 03-11-2006, 04:43 PM
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Lothar
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Default RE: Fuel system on a gasser?

Dan,

On mine... and this is my first gasser also... I have one line going to the engine, one line for fill and one line for overflow. The overflow line can be connected to a return line like the one you get with a Jersey modeler http://www.jerseymodeler.com/ fill jug that I can highly recomend. Hope this helps.

Lothar
Old 03-11-2006, 06:48 PM
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Default RE: Fuel system on a gasser?


ORIGINAL: Lothar

Hi

Can someone tell me if the plumbing for a gas motor is different than a glow setup?
I am brand new to gas and am putting a 3W 106 into a H9 EXTRA 300S looks pretty straight forward but I can't figure out the venting, does it just go overboard or is the fitting different?

Dan
I'm in the process of finishing up my first gasser which has the 3W80 and a local flyer told me that with 3W engines you don't want to put any pressure on the carb diaphram while filling the tank. That means you need to have a 3-line fueling system. Like Lothar, I have one line being used for the fill, one for the vent/overflow, and one for the clunk/carb. The carb line on mine has a T in it because the fill won't drain the tank. The T shown in the pic isn't used for filling the tank (for the reason stated), just draining it via the clunk. For overflow recovery, I have a Slimline fitting mounted in the floor of the fuselage.

Dan

Dan
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Old 03-11-2006, 06:54 PM
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Default RE: Fuel system on a gasser?

I can assure you that a 3W engine is just like all the other gassers when you fill the tank. Don't worry about the diaphram when filling. We fly some pretty exotic stuff and we don't even concern ourselves about the diaphram when we fill the tanks. A two line system works just fine.
Old 03-11-2006, 08:18 PM
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Default RE: Fuel system on a gasser?

Run a vent up and a vent down in the tank. Combine those outside the tank with a "T". Then run that across the top of the tank so you don't get any siphoning. Run the clunk line to another "T" one side of that goes directly to the carb and the other side of the "T" goes to your fuel dot. Look at the photo I attached.

Good Luck

[img][/img]
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Old 03-11-2006, 08:39 PM
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Default RE: Fuel system on a gasser?

That means you need to have a 3-line fueling system.

No, it doesn't. Simply use one of the inline gas filling valves like Dubro or Sullivan make. Both work well. You don't need Ts or anything else, since the insertion of the filling probe cuts off the carb from the line.

Dr.1
Old 03-11-2006, 09:08 PM
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Default RE: Fuel system on a gasser?


ORIGINAL: Dr1Driver

The plumbing is a little different on a gasser. Gas engines use pump-type carbs and do not need muffler pressure. Simply run one line from the tank through your fueling device and then to the carb. Run the vent line out the bottom of the plane. Don't worry about gas leaking out the vent. It won't.

Dr.1
So, this is just like the glow setups we used before muffler pressure?
Jim
Old 03-11-2006, 10:43 PM
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Default RE: Fuel system on a gasser?

Yup, Jim. That about sums it up. Very simple and easy.

Be sure your tank stopper, gas lines, filling valve and pump are rated for gasoline.

Dr.1
Old 03-12-2006, 01:31 AM
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Default RE: Fuel system on a gasser?

That means you need to have a 3-line fueling system.
No, it doesn't. Simply use one of the inline gas filling valves like Dubro or Sullivan make. Both work well. You don't need Ts or anything else, since the insertion of the filling probe cuts off the carb from the line.
True. I've never had great luck with fueling valves so I guess I subconsciously block-out that option.

Dan
Old 03-12-2006, 08:13 AM
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Default RE: Fuel system on a gasser?

Dan,

I've heard rumors that the Dubro fillers leak, but this hasn't been my experience. The Sullivan also works very well. Part of the problem may be someone just carelessly ramming the fueling probe into the port. This might damage the gasket or o-ring and cause problems. I believe with moderate care, these valves are reliable. That's been my experience with them.

Dr.1
Old 03-13-2006, 01:37 PM
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Default RE: Fuel system on a gasser?

Thanks for all the great responses and photo's, this has eliminated all the doubt I had about the vent line and leaking. Guess it makes sense, the vent has negative pressure on it while the carb is drawing fuel.

Thanks,
Dan
Old 03-13-2006, 07:54 PM
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Default RE: Fuel system on a gasser?


ORIGINAL: Silversurfer

I can assure you that a 3W engine is just like all the other gassers when you fill the tank. Don't worry about the diaphram when filling. We fly some pretty exotic stuff and we don't even concern ourselves about the diaphram when we fill the tanks. A two line system works just fine.
Thanks for the education, Pat. I also contacted Cactus Aviation and was told the same ... that a 2-line system is fine. Bobby said it would take at least 7 lbs pressure in the line to mess up anything in the carb when fueling.

Dan
Old 03-14-2006, 08:44 AM
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Default RE: Fuel system on a gasser?

Hey guys,

This is how you setup a 3 line tank?

Thanks,

John
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Old 03-14-2006, 09:26 AM
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Default RE: Fuel system on a gasser?

I like to put a second piece of tygon and clunk on the fill line, that way I can effectively pump out all unused fuel at the end of the day. This in reference to the picture in the post above, of course.

Tim
Old 03-14-2006, 09:30 AM
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Default RE: Fuel system on a gasser?

Hey, that's a good idea....

Thanks

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