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Do tanks need to be drained for fuel selector maintenance?

00Dan

Well Known Member
I have an old brass 3 port fuel selector on my plane and the handle seems quite stiff; partially due to location but it has recently taken two hands to turn in flight. Obviously this is not acceptable.

I found a schematic in the archives and plan to disassemble and lube it, but before I do, do I need to drain the tanks? This is for a taildragger, if that makes a difference.
 
RV6A - I took the valve apart and fuel shot up hitting me in the eyes. I plugged the valve with one hand and rebuilt the stem (new o-rings) one-handed with the other hand, all while blind and with burning eyes.
I would drain them...
 
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I did this last fall on my 6A and did not drain the tanks, though I believe they were 1/2 full or less. You can measure the height of the lines entering the selector and compare to the fuel height in the tanks. If the latter is lower than the former, you will be fine. Basic gravity at work. Some cleaning and a new o-ring returned lever operation to normal.

Pretty certain you will have issues if the tanks are full.

Larry
 
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Dan, after disassembly, if you find the center core is the old brass kind, it would be wise to change it out for the newer nylon core valves (brass housing, nylon core). I remember Vans changing to the nylon type valve because of the issue you are experiencing.
 
RV6A - I took the valve apart and fuel shot up hitting me in the eyes. I plugged the valve with one hand and rebuilt the stem (new o-rings) one-handed with the other hand, all while blind and with burning eyes.
I would drain them...

What, no video?
Sorry, but that made me laugh!
 
I’ve done this same thing 4 times in the last two months. I had to drain my tanks down to about 1/2 to prevent fuel spillage.
Mine also got difficult to move, and mine has the nylon core. I was using fuel lube on it and that only kept is lubed for about 5 tank changes, then got stiff again. So I again took it apart and lubricated with EZ Turn and replaced the o-rings. That kept it good for about 10 fuel tank changes before stiffening up. So off it came again, and this time lubed with Krytox. That was the worst one of all. It took all I had using both hands after only a few tank changes. This time I removed it and tossed it in the trash can. I ordered a Newton SPRL valve from Spruce, which required re-plumbing and a small change in selector valve location on my RV4 because of geometry. The SPRL valve is very nice, easy to operate, and requires no lubrication. It is a make before break valve and can actually flow fuel from both tanks at once if you leave the selector in the middle between L and R (not a normal procedure).
 
Changed mine out

After having a complete engine failure/die at 200 ft off the ground on take off and successfully dead sticking the plane back onto the runway. Chasing the problem back to worn out fuel selector I changed mine out

Put in new Andair. It was kind of expensive and required total re plumb of the lines.

But was worth it.
 
Dan, after disassembly, if you find the center core is the old brass kind, it would be wise to change it out for the newer nylon core valves (brass housing, nylon core). I remember Vans changing to the nylon type valve because of the issue you are experiencing.

You can determine this before taking it apart.

The original valve with the brass cone only has 3 ports. An input port on each side for each tank and an output port on the front or back (depending on how it is installed).

The newer style valve has 4 ports total. 3 on the sides (with one typically plugged when there is only two tanks), and an outlet port on the bottom.

Basically, if the valve has a port on the bottom it is the newer style.


Servicing the valve requires reducing the fuel level in each tank so that it is lower than the level of the top of the fuel valve in the cockpit. 1/3 full or less is usually sufficient.
 
My fuel selector is the original Vans type supplied with the kit. (I completed my build in 2012). Mine was getting stiff to turn not long after beginning the flying after completion of the build. I started squirting a little WD-40 on the stem. It eventually runs down and makes it way to the inside. Worked great and still does to this day. About 3-4 times a year I do this and have never had any more issues. Nice smooth transition between L/R tanks and I can feel the little "click" when in the right spot.


I did completely remove the selector a few months ago because I was changing out a fuel line. You can do this with the tanks full if you want. I opened the wing root and with a cap handy removed the fuel line just outside of the wing rib. Cover with finger then quick like a bunny put a cap on. Very little fuel spilled.
 
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Thanks for suggestions, all.

My tanks were about half so to be safe I drained about 5 gallons from each. I do indeed have the three port selector with the brass core. It took some work to get it to come free and when it did I noted some rotational scoring but no grooves or deep wear. After a coat of EZ turn it now turns freely.

Was the periodic maintenance the driver behind switching to the nylon core? I’m wondering what priority I should give such a purchase since it seems my brass core still functions normally when it’s actually lubricated properly.
 
It was changed for a number of reasons.
One of them being that it does require maintenance.
With proper maintenance they will work fine for a long time.

The original prototype RV-6A ("old blue") is 34+ years old and has over 5000 flight hours and still has the original style valve though I think the entire valve was changed a few years ago with a new old stock one that we had on hand. Even so, it had a lot of years and hrs on the first one and has accumulated many more since it was changed.

As part of maintaining the valve, if there is visible scratching/scoring on the cone, I recommend some light use of 600 wet/dry sand paper and then finish with fine scotchbrite (you don't have to 100% remove scratches, just get it smooth) and then lube (fuel lube, easyturn, etc) before reassembly.
 
My A&P instructor told our class that he has used Mother's Mag/Aluminum Polish on the guts of fuel valves to make it operate smoothly. Chuck it in a drill press and polish it to a mirror shine.

I've not personally done this (I've got an Andair valve), so your experience may vary...
 
Valve spring

I seem to remember an article from "wayback" that described a mod to the valve to make it easier to turn.

The mod involved removing the core and the spring, and then cutting the spring to make it shorter to reduce the force on the core.

Anybody remember this??
 
Quick note about EZ-Turn and other fuel lubes, a takeaway from the Airflow Performance school...

Excess fuel lube doesn't readily dissolve, so it's a common contaminant found when overhauling fuel injections. Use very sparingly! Just a very thin film, never enough to squeeze out.
 
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