Fuel Selector Drain Valve (WAS) Leaking

[RLCarter]

So the other day was getting ready to go up with my CFI to do some maneuvers, after filling up I sumped the tanks and after boarding pulled the ring on the gascolator (which seemed harder than normal?) and it wouldn't stop flowing fuel from the fitting unless the valve was in the "OFF" position. The plunger seem to return to the full down position and I even pushed with my thumb but it was still puking fuel, I scrubbed the flight and towed it back to the hangar. This morning I placed a pan under the plane and turned the fuel back "On" and no more fuel flowing on the ground, A&P had me remove the LH fairing to gain access to the Valve Assy., there were no signs of fuel leaking in the past. We pulled the drain ring 5 or 6 more times and everything was normal, I left the fuel valve "On" while at lunch and sumped it several more times throughout the afternoon. Anyone have this happen or have any ideas? This wasn't a drip it was "Flowing" out as if the plunger was pulled, I had the plunger on the 172 replaced a little over a year ago and was wondering if the plunger can be had for the Mooney? A&P wanted to pull the Valve until I told him there was 52 gal of fuel and the 172 was full too. 

[carusoam]

wait a sec...

Selector valve or separator drain?

It is only going to drain 26 gallons at a time... 

The drain valve Has a rubber tip Glued on it...

Sounds like you experienced some dirt in the system keeping the valve from closing...

Of course, now that it works, you may not know what the source of the dirt was, or if it was only one piece...

It may have some brothers...

My 65C used to pass rust particles this way... they were small enough to fall through all the screens... and collect in the separator, sort of...

At annual, do you see any rusty water in the separator? Or any rusty bits?

If you do... have a look for rusty fuel neck rings... a more common source for rust in your fuel...

Rust particles should make you nervous... I wasn’t bright enough to know any better... 

Drain lots of fuel through the valve and collect it in a glass jar... see if anything else funny shows up...

All the fuel can be put right back in the tank if it is clean...

 

Now the other thing... the fuel selector valve itself... if that is leaking... that is a different problem... when it wears, fuel  leaks out... while it sits...

When you fly, air leaks in... this can be problematic when too much air comes with the fuel... it also really disrupts the FFsensor... it counts air bubbles as gallons of fuel...

The whole device can be OH’d, Lasar is the resource...

 

There are stainless replacement parts for the fuel neck...

PP thoughts only, not a mechanic...

Best regards,

-a-

 

[RLCarter]

Have never seen anything but 100LL when I sump the tanks, fuel tanks were opened up a few years back to calibrate new sending units and all was clean, other than a really messy tank seal job. After removing the sealant for the top inspection panels the tanks were vacuumed out, wiped out and vacuumed again to insure no removed sealant was left behind. I've had debris under the plunger in other aircraft and they dribble, but this was a full flow situation. We haven't checked the screen in the gascolator yet (spare gasket was 25 miles away) but that's on the agenda for Wednesday when he can get back out.... I don't like things that are broken and I really don't like things that seem to just go away. I ask "Why" a bunch, might not like the answer but I still ask...