Fuel Valve and Gauge Check

[DanH]

For this annual I removed the stock Vans fuel selector valve for an inspection. Lots of builders substitute Andair valves, and yes, they're nice, but I had pulled this one apart when new, about 740 hours ago, and didn't find anything objectionable. Still don't.

Goes together like this:



Two details: Do not lube the nylon spindle with EZ-Turn fuel lube, or if you do, be extremely sparing..barely enough to know it's there. Even a thin film is likely to be scraped off and wind up in the downstream fuel filter, or worse, in a carb or fuel injection jet.

Second, install the o-ring into the cap with some EZ-Turn to stick it in place, then put a dab on the shaft. Now push the cap down the shaft and screw it into place without backing up. If you pull the cap up the shaft, the o-ring will pop out of the cap due to shaft friction, and there's a good chance it will not re-seat back into it recess. BTW, lube in this upper section of the valve won't hurt anything; there is no fuel flow up around the shaft.



Pulling the valve means draining the tanks. (Do that with a grounded metal defueling funnel please.) I just pull the drain valves with the tail raised to level the longeron. With the tanks empty, there is an opportunity to confirm fuel float sender calibration at low fuel levels.

Like most I ignore the float gauges until several hours into a flight, as they physically can't offer an accurate reading until the fuel level drops below the top of the inboard bay. Until then, it's all totalizer and wristwatch. However, the gauges are useful in the last stage of a long flight, to confirm the totalizer and whatever mental fuel calcs you may have running.

The check is simple. Start with the tanks dead empty. Install the drain valves. Confirm the gauges read zero or similar. Now add exactly two measured gallons to each tank, and check the gauges again.

In my case I had readings of 1.0 and 1.7 with two known gallons in each tank. I could probably tweak the EIS settings and make it perfect, but it's really close enough. The point is just to know that they're not lying, and usable fuel should be at least what the gauges show...not that I ever intend to get both of them at low at the same time.

[JonJay]

As always, excellent write up with pictures and procedures. At 750 hours, I contemplated doing this. I had enough to do for that CI and chose to replace the valve, $53 new, from Vans. My old one is sitting here waiting for a spare moment and when I get it, I will follow your guide, rebuild it, and swap it out next time. Of course, that won't need to happen for some time, and by then, who knows, I might just spend another $53.
Regardless, you continue to provide high quality resources to this site. The anatomy of the fuel valve in pictures is awesome. Simple, reliable, bulletproof design. That is what I want in my fuel system.
Thanks for taking the time to share this.

[gasman]

Originally Posted by DanH

.............
To add to Dan's post....

If installed with servicing in mind and you leave access to the cap, you can service this valve without removing any plumbing.

The only parts to replace are the 2 "O" rings and they can be purchased at any Auto Parts store.

Also, instead of cross plumbing to make the valve handle point properly, just plumb right to right and left to left. And then just drive the pin out of the spindle and shaft and rotate the spindle 180*.

If the valve continues to turn very hard, try a weaker spring. Too weak and the detent washer will tilt and cause binding also. I removed mine and am very pleased how very smooth the valve operates. Without the detent washer, the valve DOES still stay in place.

My valve was installed with EZ turn (fuel lube) only on the "O" rings. This spindle was installed dry.

....... If you do alter the valve, tag the valve explaining the alteration......

[AlexPeterson]

I'd be curious how the torque to rotate the valve would increase, if any Fuel Lube is on the nylon spindle, and the valve is put in a freezer. That stuff gets really viscous when cold.

[gasman]

Originally Posted by AlexPeterson

I'd be curious how the torque to rotate the valve would increase, if any Fuel Lube is on the nylon spindle, and the valve is put in a freezer. That stuff gets really viscous when cold.

It does cause a lot of drag on the spindle even at room temp. The spindle is designed not to be lubed. The nylon and brass, seat just fine dry.

The stock spring will press the spindle into the brass seat with too much pressure and cause the valve to eventually turn very hard. To prove it, just reach under the handle with two fingers, lift and turn the valve.

[BillL]

Nice visual and text report Dan. I had one in my '77 Chevy pickup truck for tank selection. I just ground off the pointer, which could not be seen anyway and used the handle as the pointer. Easier to determine under the seat anyway. It lasted 20 yrs before the operating torque became excessive.

I just replaced the valve, but contacted the manufacturer for consultation on replacement parts. They do not provide parts nor recommend repair, not a big surprise, labor cost would surely exceed the replacement cost. On mine, the shaft o-ring was the issue, it deteriorated with ethanol gasoline (assumed) and extruded up along the shaft and threaded cap. That is what caused the increased operating torque. It maybe the primary cause for others as well, but maybe is an important word.

I have not researched the o-ring sizes needed, so if someone has the dimensions I would appreciate a posting so Viton o-rings can be sourced (compatible with ethanol). It is way down on my to-do list right now.