air in fuel line of glow engine

by rick
(urbana)

i just dont get it, i have changed all fuel lines, tubes, the top part that supports fuel tubes and im still getting air into the inlet fuel line, can you please help before i crash this thing?

thanks

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air in fuel line of glow engine

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Jul 28, 2009
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filled tank?
by: Anonymous

Are you filling the tank until gas comes out the xaut line? Make sure you are filling the tank to push all the air out

Jul 23, 2009
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air in fuel line
by: Anonymous

thanks for your reply matt,

the engine is about 7or 8 yrs old and it has one line to the needle valve and one line two the exhaust.

when i took the tank out of plane im wondering if the fuel line that is inside the tank slipped or was pulled by the clunk part, and hitting back part of tank.

ill find out tommorow when i check it out, it rained all day yesterday and today. but anyway the air that i noticed was visible before the needle valve and i couldn't tell if it was before the inline filter.

the day i was flying the plane it shut down 3 different times all in mid flight. would really like to find the cause.

Jul 23, 2009
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aluminum or brass, doesn't matter.
by: Matt

It doesn't really matter if it's brass or aluminum, as long as it's air tight.

Is the air in the line before or after the high speed needle?

Jul 22, 2009
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air in fuel line
by: rick

thanks matt for comment
does the fuel tubes have to be aluminum, i have brass, and i did do the leak test and i passed this test, although i have an 060 towers hobbie
trainer and the tank fit is so tight that it is impossible to wrap foam around it unless i do some serious restructuring.

Jul 22, 2009
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No, don't crash!
by: Matt

Hi Rick,

Unfortunately I can't keep ya from crashing the thing, but may be able to help you figure out this air problem of yours.

Take a look at the image below. Make sure the exhaust line is but upwards like in the picture. I am sure you have check this already, but I just want to cover all the bases.

Vibration can also cause the fuel to foam leading to air in the fuel line. Make sure the tank is wrapped in foam if you have the room. Also make sure the prop is balanced to prevent excessive vibrations.

I have heard of people adding a drop or two of Armor oil to prevent fuel from foaming. But I believe most fuels these days already have additives to help minimize the foaming.

You may also have a pin hole in the tank or the new tubing and fuel line. It's rare, but you could have a hole in the new tubing and lines you just installed. It's good to check everything.

A good way to test is to fill your sink or a bucket with water. Submerge the entire tank and fuel lines under the water. Pinch the exhaust tubing closed and blow into the fuel line and watch for air bubbles (or vise versa).

Please let us know what you find!

RC airplane fuel tank clunk

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Jul 22, 2009
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Submitted by: Matt

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Comment
Hi Rick, Unfortunately I can't keep ya from crashing the thing, but may be able to help you figure out this air problem of yours. Take a look at the image below. Make sure the exhaust line is but upwards like in the picture. I am sure you have check this already, but I just want to cover all the bases. Vibration can also cause the fuel to foam leading to air in the fuel line. Make sure the tank is wrapped in foam if you have the room. Also make sure the <a href="http://www.hooked-on-rc-airplanes.com/model-airplane-propellers.html#4">prop is balanced</a> to prevent excessive vibrations. I have heard of people adding a drop or two of Armor oil to prevent fuel from foaming. But I believe most fuels these days already have additives to help minimize the foaming. You may also have a pin hole in the tank or the new tubing and fuel line. It's rare, but you could have a hole in the new tubing and lines you just installed. It's good to check everything. A good way to test is to fill your sink or a bucket with water. Submerge the entire tank and fuel lines under the water. Pinch the exhaust tubing closed and blow into the fuel line and watch for air bubbles (or vise versa). Please let us know what you find! <img border="0" src="http://www.hooked-on-rc-airplanes.com/images/RC-fuel-tank.jpg" WIDTH="359" HEIGHT="170" alt="RC airplane fuel tank clunk" ALIGN="center">

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