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Air in fuel line

Old 06-07-2008, 06:56 AM
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Default Air in fuel line

Hi All, Was wondering if any one had some advice as to a problem I'm having. I have an SSE with an Evo. .46 built from a kit. The fuel tank is the recommended Du-Bro for this build. It seems that at 1/2 to 2/3 throttle I get air bubbles in the fuel line and the engine starts to porpuse in rpm. Go to full throttle and it seems to run fin. I seen these bubbles on the bench with it running. I have had to dead stick it when it quit on me at 1/2 throttle. the tank has been pulled and found to have a stopper that I thought was kinda loose, but not leaking. Rechecked all plumbing and reinstalled and I still get airbubbles at part throttle operation. Any Ideas?? Thanks in advance, Joe.
Old 06-07-2008, 07:04 AM
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Default RE: Air in fuel line

Try wrapping it with some foam? Cuts down on vibration induced air. If the bubbles are small, you have some kind of an airleak. Just replace the line on draw line to the carb, that usually takes care of it. That covers the 2 types of air that you can get in a fuel line that I know of. Make sure you snug the stopper down well, also.
Old 06-07-2008, 08:32 AM
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Default RE: Air in fuel line

I've also found the metal tube cracked a time or two allowing air into the draw line. Inspect everything well. The draw line attached to the clunk can be another source of problem as well.
Old 06-07-2008, 10:09 AM
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Default RE: Air in fuel line

put about 5 drops of armor all in your gal fuel jug and you will never see air again Terry
Old 06-07-2008, 01:54 PM
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Default RE: Air in fuel line

Terry, most of the current fuels already have anti foaming agents.

I've never wrapped my tanks and foaming isn't an issue. I fly four strokes, 52 thourht 91 sizes, so there is a lot of thumping of the air frame.

As others have pinted out, start at the clunk and work forward. I will just replace all of the lines and make sure the brass tubing is OK. If you go throug the effort of pulling the thank, it is eaiser to eliminat everyting at once vs three or four trips in. It also saves wear and tear on the plug.

Don
Old 06-08-2008, 05:58 AM
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Default RE: Air in fuel line

ORIGINAL: Campgems

Terry, most of the current fuels already have anti foaming agents.

I've never wrapped my tanks and foaming isn't an issue. I fly four strokes, 52 thourht 91 sizes, so there is a lot of thumping of the air frame.

As others have pinted out, start at the clunk and work forward. I will just replace all of the lines and make sure the brass tubing is OK. If you go throug the effort of pulling the thank, it is eaiser to eliminat everyting at once vs three or four trips in. It also saves wear and tear on the plug.

Don

I second that Don. Most Arfs it is hard to wrap a tank with foam... there just isn't any room! If you can wrap a tank with bubble wrap or foam, it will take out some of the vibration that can cause the foaming effect in your fuel line... especially if your prop is not balanced.

Have a well balanced prop, and you won't have much of a problem. I don't wrap my tank either most of the time.

JMPE


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Old 06-08-2008, 06:37 AM
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Default RE: Air in fuel line

Thanks for all the suggestions, will pull tank again and redo all plumbing. Joe

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