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  #1  
Old 02-09-2022, 08:20 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
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Default Fuel Valve O-Ring

I had previously lubricated the standard Vans brass valve with a very thin film of EZ Turn. It was fine initially, but over time it became difficult, I think more so than a valve assembled dry. So, given its non-performance, coupled with the bad habit of clogging fuel controls, henceforth I'm consigning EZ turn to some dark corner, perhaps never to be seen again.

This time the valve went back together with a very thin film of Krytox on the Delrin spool. Bill Lane investigated and recommended Krytox for fuel cap o-rings, for which it has proved to be wonderful. At this time the valve operates like butter. I'll report in a year.

The interesting point was the stem o-ring. I suspect it gets overlooked a lot. On close examination, it appeared to not be in full contact with the stem under all conditions, having become a bit hard, squared in cross section, and shrunken. See the photo. I'm pretty sure they started life as the same size.

Here's the thing...a leaky o-ring has the potential to allow sucking air into the fuel system prior to the boost pump. It would also need to leak past the spool-to seat contact, which is not inconceivable. A few times in the past year I've seen random fuel pressure reductions during steep climbs, with no obvious cause, boost pump on or off. Well, air bubbles will do it. We'll see how she does in the coming months.

Yes, I know Andair valves are popular...
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  #2  
Old 02-09-2022, 08:59 AM
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I've found that a drop of machine oil on the stem at every condition inspection keeps the valve operating happily.
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  #3  
Old 02-09-2022, 09:19 PM
vluvelin vluvelin is offline
 
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Dan what is the part number for O ring?
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  #4  
Old 02-09-2022, 10:24 PM
gasman gasman is offline
 
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Location: Sonoma County
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Default

There should also be an "O" ring on the cap that should be replaced.
Take your used O rings to any ACE Hardware to find replacement parts if using 100LL..... Auto fuel requires a compatible product.

It's not a case of lubrication, the cone is self lubricating against the brass. The problem is the spring is too firm and forces the cone to bind to the brass. To prove it to yourself, place two fingers under the handle and lift slightly and turn.

I cut out one loop from the spring, and with no lubrication, have had a glass smooth valve ever since.

The valve can be serviced without removing any fuel line fittings.
Back the handle screw off two turns, pull up on the handle to unseat it. With fuel level below the valve, unscrew the cap.
Now lift the handle, shaft and cone from the body.
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Last edited by gasman : 02-09-2022 at 11:31 PM.
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  #5  
Old 02-10-2022, 03:45 AM
almarsh almarsh is offline
 
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Location: grain valley mo
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Default Valve

Good write up I have had this issue for sometime now have been worried when I switch tanks I can hear it and feel the friction when turning, my word I say what if this handle breaks off or stops turning in flight then it would be very big problem has there been ad on this ?
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  #6  
Old 02-10-2022, 05:43 AM
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decathlon737 decathlon737 is offline
 
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Default EZ Turn

[quote=I'm consigning EZ turn to some dark corner, perhaps never to be seen again.-[/QUOTE]

I thought EZ Turn was used in your socket to hold the nut in place for hard-to-reach places you hand won't fit into.
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  #7  
Old 02-10-2022, 07:41 AM
NTex NTex is offline
 
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Dan, good investigation.

Curious what type of fuel you run and what the material of your o-ring is... maybe buna-n?

I'd look hard at a flourosilicon or viton o-ring; shouldn't shrink or take too much compression set with various aromatic fuel contents.
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  #8  
Old 02-10-2022, 08:42 AM
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DanH DanH is offline
 
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100LL. It's probably buna. Yes, blue flourosilicone might be better.

Part of the problem is the hole in the brass cap is overly large, so the shaft can rock around a bit, and the o-ring can't stay sealed at the extent of movement. Obviously age and shrinkage makes it worse.

I'm thinking about soldering a sleeve to the cap to hold a lip seal, or machining the cap to press one in....but you know how I love overkill.
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Last edited by DanH : 02-10-2022 at 09:27 AM.
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  #9  
Old 02-10-2022, 08:47 AM
David Paule David Paule is online now
 
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Dan, which species of Krytox is that?

Thanks,
Dave
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  #10  
Old 02-10-2022, 09:26 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by David Paule View Post
Dan, which species of Krytox is that?
Krytox GPL-205

https://www.amazon.com/Chemours-D124.../dp/B073Y4557Y
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