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Fuel Valve O-Ring

DanH

Legacy Member
Mentor
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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I've found that a drop of machine oil on the stem at every condition inspection keeps the valve operating happily.
 
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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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 ?
 
EZ Turn

I'm consigning EZ turn to some dark corner said:
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. :D
 
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.
 
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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Doesn't seem to do the job.

I have found the same results. After I got over the elevated cost of the Krytox
I shut up. Paid the Piper and found it better.
I too have send the EZ-Turn to the dust bin. Had two tubes and hated to throw it away But, It has failed me in many locations it was supposed to work in.
Thanks for the post Art
 
Dan, What was the time in service, (in years), for that valve? I have the same type and after a few years it began felling a little sticky. My solution was to spray the shaft with a squirt of WD 40. It's thin so my thinking is it would run down into the valve better. It worked. Silky smooth. I give it a squirt every 6 months or so.
 
Dan, What was the time in service, (in years), for that valve? I have the same type and after a few years it began felling a little sticky. My solution was to spray the shaft with a squirt of WD 40. It's thin so my thinking is it would run down into the valve better. It worked. Silky smooth. I give it a squirt every 6 months or so.

Valve is 11 years in service. Last lubed with EZ Turn in Jan of 2018. It didn't stay EZ very long.

You could be entirely correct about the WD running down the shaft. See Bob's post about a drop of oil.

Here I wanted to bring focus on the o-ring, as it is probably overlooked by most.
 
Another option is to replace that brass valve with the Andair valve. They don’t leak air like the brass ones do. I have see the leaks in the brass ones cause the pressure fluctuations as well.

Vic
 
Mine is 12 yrs old and I have never done anything to it. Perhaps I should.

After Paul Dye had the experience of the selector knob turning on the shaft, leaving the valve in an in-between state, (fortunately within glide of an airport) I installed my selector knob so that it will probably never come off. The set screw that goes into the hole at the point of the arrow was put in with loctite, and I don't think I will be able to remove that without stripping the Allen socket of the set screw, or twisting the Allen wrench. So I will likely have to cut the shaft to get it out, and replace the valve.

In doing so, I'm willing to consider a retro-fit to the Andair valve. But it looks like the attachments are totally different. I'd rather not make new fuel lines. Is there a combination of fittings that would make adapting to the new valve simple?

Appreciate info from anyone that has done this
 
Mine is 12 yrs old and I have never done anything to it. Perhaps I should.

After Paul Dye had the experience of the selector knob turning on the shaft, leaving the valve in an in-between state, (fortunately within glide of an airport) I installed my selector knob so that it will probably never come off. The set screw that goes into the hole at the point of the arrow was put in with loctite, and I don't think I will be able to remove that without stripping the Allen socket of the set screw, or twisting the Allen wrench. So I will likely have to cut the shaft to get it out, and replace the valve.

In doing so, I'm willing to consider a retro-fit to the Andair valve. But it looks like the attachments are totally different. I'd rather not make new fuel lines. Is there a combination of fittings that would make adapting to the new valve simple?

Appreciate info from anyone that has done this

Steve - I replaced the tractor valve with an Andair about 12-15 years ago. I had set my original valve up to be a 90 degree rotation between L and R tanks, not wanting a "dead" space between when using 180 degrees. The Andair install was quite easy, and the fittings lined up fairly well. (Easy, as in still a lot of work, like all projects...) I may have had to modify/replace the center tube, but I don't recall.

I think it would have worked equally well if I had the original one set for 180 degrees.

Now back to our regularly scheduled program of O-ring discussion - as was said earlier, Viton is an excellent choice. They are the brown ones. I would not get it at a hardware store - who knows the history of one of them, and I suspect they won't have Viton. I've had Viton on my fuel cap o-rings for many years now with no problems. Again, as mentioned earlier, flouropolymers tend to be less prone to stress creep (your flattened O-rings Dan).
 
Mine is 12 yrs old and I have never done anything to it. Perhaps I should.

After Paul Dye had the experience of the selector knob turning on the shaft, leaving the valve in an in-between state, (fortunately within glide of an airport) I installed my selector knob so that it will probably never come off. The set screw that goes into the hole at the point of the arrow was put in with loctite, and I don't think I will be able to remove that without stripping the Allen socket of the set screw, or twisting the Allen wrench. So I will likely have to cut the shaft to get it out, and replace the valve.

In doing so, I'm willing to consider a retro-fit to the Andair valve. But it looks like the attachments are totally different. I'd rather not make new fuel lines. Is there a combination of fittings that would make adapting to the new valve simple?

Appreciate info from anyone that has done this

Steve, I do really like the Andair valve in my -8, but I’ve just used the brass tractor valve on all the airplanes since then, and they work fine, so I doubt I’d ever go to the effort of re-running fuel lines just to get an Andair in an aircraft that had a brass valve. And there are valve handles that look nice and don’t require the set screw anymore….. ;)
 
Dan is right - Check the Oring

I also had some recent variability in the fuel flow pressures (0-360 with standard carb) Have about 260 hrs on the plane (valve movement was never considered "sticky") and when I pulled the standard vans fuel tank selector valve this weekend, the O ring around the valve stem had some little brass flakes on it.

The O ring didn't look nearly as bad as Dan's did, but after putting in a new O ring with a little machine oil on it, the first test flight was rock solid on the fuel PSI. Did not really see any noticeable amount of resistance required to move the tank selector after the O ring replacement.

Thanks Dan for sharing this info.

Paul
 
Performed overhaul last fall just as Dan did here...replaced o-rings and used Krytox. Valve is smooth as butter now and detents are more defined.

Added benefit...found last installer used teflon tape for AN816 nipple. :eek:

If anyone is wondering...here are the o-ring part numbers (non-ethanol):

O-rings: fuel selector shaft - Dash 011 (MS29513-011), cap - Dash 018 (MS29513-018)
 
Fuel selector

I burned the fuel out to 5 gallons per side. Took the selector apart, cleaned it up and put the proper lubricant on it. It is smooth but hard to move, detent is perfect. My fuel pressure is much better, higher in the climb. I suspect that I was sucking some air. I replaced both “0” rings. I can live with it being stiff as long as it is smoth.
 
I burned the fuel out to 5 gallons per side. Took the selector apart, cleaned it up and put the proper lubricant on it. It is smooth but hard to move, detent is perfect. My fuel pressure is much better, higher in the climb. I suspect that I was sucking some air. I replaced both “0” rings. I can live with it being stiff as long as it is smoth.


Fred, what was the "proper lubricant"? If it's hard to turn when lubed with a tiny bit of Krytox, somethin' ain't right.
 
Krytox

I did use krytox, I put a small amount on the bottom and on the “0” rings. I can fly the fuel off and try again. Could I have over tighten the top?
Thanks Dan.
 
I did use krytox, I put a small amount on the bottom and on the “0” rings. I can fly the fuel off and try again. Could I have over tighten the top?

I don't think it's possible to bind rotation no matter how much the top is tightened. The axial shaft pressure is a function of the spring.

If the tapered part of the white nylon spindle is lubed it should turn easily. I dunno. A bit of grit in there?
 
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