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YS check valve

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Old 03-28-2017, 03:19 PM
  #1
kenh3497
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Default YS check valve

My Smaragd (YS140DZ) had a YS check valve on the vent line to the fuel tank. What purpose does this valve serve other than prevent fuel from exiting the vent line which it shouldn't do anyway. The tank is not pressurized so no check valve needed for that purpose. Just another way to sell parts??? Why not just have the vent exit outside the fuselage?

Thanks!

Ken
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Old 03-28-2017, 05:51 PM
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You hit the nail on the head Ken, it's just there to stop fuel falling out when the vent is lower than the fuel level.

Agreed, in a perfect world this shouldn't happen when your engine is sucking on the other line, however I'm going to stick my neck out and say that the air pressure in and round your tank (and vent exit point) can fluctuate depending on which way your plane is pointing relative to the wind and how fast it's going, so it might not always be the case that the pressure in the tank is lower than the pressure at the vent exit point.
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Old 03-28-2017, 07:22 PM
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Quote:
Originally Posted by bjr_93tz View Post
You hit the nail on the head Ken, it's just there to stop fuel falling out when the vent is lower than the fuel level.

Agreed, in a perfect world this shouldn't happen when your engine is sucking on the other line, however I'm going to stick my neck out and say that the air pressure in and round your tank (and vent exit point) can fluctuate depending on which way your plane is pointing relative to the wind and how fast it's going, so it might not always be the case that the pressure in the tank is lower than the pressure at the vent exit point.
Well..... Because I do everything the hard way...... I'm going to run a vent line so it exits outside the fuse and deal with the consequences later. It takes a bit of "pressure" or in this case suction to open that valve. In my own mind I feel I need to eliminate complexity. In this case it puts an extra load on the fuel pump. I can always put the check back in the line.

Ken

PS. 100 of you can tell me NOT to do something but because I'm a stubborn old fart I'll still try it
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Old 03-28-2017, 09:55 PM
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That's fine.

Anyone blindly accepting engine advice from me at the moment probably has other issues they should be seeking help for....
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Old 03-29-2017, 04:06 AM
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Quote:
Originally Posted by bjr_93tz View Post
That's fine.

probably has other issues they should be seeking help for....

HA... I resemble that remark! LOL
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Old 03-29-2017, 05:17 AM
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The check valve is mainly there to prevent fuel from pouring out of the vent when the caller picks up the plane by the nose and carries it nose down back to the pit area. Without the check fuel pours out all over the caller.
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Old 03-29-2017, 05:22 PM
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Ken, I don't use a check valve on my DZ 140. It's not been an issue.
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Old 03-29-2017, 07:36 PM
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True, but you do use special fuel in your 140, that makes the difference.
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Old 03-29-2017, 07:58 PM
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If I recall correctly the trend was to do away with the check valve, wrap the fuel line around the tank to prevent siphoning out the vent line. You can either run the vent line out the bottom, or drill a hole in a fuel dot.
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