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Fuel Drains

NunavutPA-12

FRIEND
67.8N,115.1W CYCO Canada
I'm getting tired of replacing those Saf-Air fuel drains. They don't seem to last long before they start to drip.

Is there a better alternative? I think I'd prefer a simple valve with a 90-degree handle.

Experimental PA-12.
 
The drain holes are small and any ice or debris of size gets jammed between the O-ring and base on closing. Alcohol in fuel and some motor gasoline can swell the O-rings enough to dislodge them. The O-rings eventually flatten and get hard to reseal especially when cold.

In winter freeze the fuel first to help crystallize water and use a good filter. If there's a finger screen on the tank or sump to engine plumbing it can trap things but they won't get removed unless the tank is flushed. Even if we filter the fuel bugs crawl in the tank vents. Cubs and others with large upright vent tubes are bad for that. Cover them with a fine mesh something or stuff a well marked soft cleaning brush in the hole between flights. Lets the tank breathe with temp changes.

But yes Larry there's probably something better.

Gary
 
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It's pretty easy to just replace the O-rings periodically, if they're a problem.
Just 1) have a spare drain valve (or plug-type fitting of the proper thread) to temporarily substitute for the one being repaired,
and 2) wrap an old sock or something around your wrists to prevent an armpit full of gas.
 
Yea, been there/done that. Gas sure does burn the armpit even when not lit.:oops:
 
Plug the tank's vent before draining - it slows the flow of fuel.

Last summer I was having issues with quick drains on my plane. Drips after draining from small debris. I emptied the wing tanks via a 1/8" NPT hose fitting in the drain location and long fuel hose laying in a metal bucket on the ground. Helps to electrically bond everything and have fire extinguisher nearby. Gas that drops free can blaze up from static. Know of a Cub that did that. Then I raised the wing and poured fuel into and through each tank to flush debris and maybe clean the outlet finger screens some. Got lots of paint chips, bug parts, and rodent hairs or spider web stuff not sure that was too big to pass the quick drains. Then replaced the O-rings with original parts not some NAPA crap of unknown type.

Gary
 
I've had the drains themselves get kinda plugged up with extremely small brown "stuff"--
looks like maybe residue that flaked off the inside wall of the tank.
I wonder if blowing up through the drain with shop air might be helpful in keeping the drains clear & tight?
Sure easier than R&R'ing the quick drains.
 
Brown stuff: Fuel filter media - internal fuel hose media - fuel tank bladder media - or as you mention maybe some other residue? If fuel cap vents open to dirt and dust then that too.

I have observed a mechanic use a rubber tipped air nozzle to gently blow back through the drains after he pushed them open. No explosion that time. Might work but then the goobers would still be lurking in the fuel.

I temporarily plugged my cap vents as mentioned above and did a quick R&R with a capped barbed hose adapter. Once the hose adapter was inserted I removed its cap and pushed on the drain hose to the bucket. All done outdoors of course. Hose can be pinched over or a valve in the hose to stop the flow. I kept the adapter cap handy.

The fellow I know with the Cub that burned reportedly drained fuel on the ground or container from the wing. Fire started on the ground. He pushed plane away but the fire followed and eventually burned things. No way to plug the drain in time.

Gary
 
I don't see many issues with them. Are you getting debris stuck in them or the o'rings wearing or what? I keep a spare, if it leaks I pull it and install my spare. Slap a new oring on it and now it is the spare.
 
The biggest problem I've had is in winter below freezing. Ice crystals in the fuel can jam and cause leaks. Unless there's a real need I leave the wings alone and dump the filter and carb after they are preheated. Sometimes they can freeze shut after pushout from a warm hangar if not drained soon.

I know of a fellow Cub that had a fuel line freeze between the tank and filter. He couldn't get it to flow and we landed our planes and transferred fuel from the blocked tank to the near empty one with a empty can I had aboard. Not sure where or when the blockage happened. We were trapping and the planes had been cold soaked for a day.

Gary
 
My experience is that those drain valves are pretty reliable unless, as others have noted, you've got "stuff" in your gas or the O-rings are shot. It's possible to get a piece of something caught in the valve and damage the O-ring.

If you're using auto fuel, that may affect the O-rings as well.

MTV
 
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I switched to these on my left tank and gascolator. Makes draining simple, add hose and turn to stay locked open

Glenn
 

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My left tank drain and fuel cap on the Maule has been freezing up all winter, figured it s condensation from warm fuel being pushed in from the injector pump return. When things get warm enough I drain it and there’s usually just a trace of water. The other 4 drains are fine, It’s a pita and I keep a spare drain just Incase


Sent from my iPad using SuperCub.Org mobile app
 
24 years in the air on mine and yet to drip or replace an o ring on my 4 x CAV-110's. Nothing but 100LL. Auto fuel eats them on a regular basis for some of my customers though and then I do as noted above... the QUICK swap.
 
I've used one of the wife's old hair dryers to quick thaw drains. Seems she cycles through them regularly and they can be used to preheat the engine and plane innards. Honda genset and oldest appliance.

Gary
 
I do the swap thing also. When I do the swap I wait until the tank is less than 1/4 and then jack-up the opposite side axle to get the fuel to run away from the drain.

MOGAS eats the aviation o-rings but since I started getting the o-rings at NAPA I haven't had any problems other than mechanical damage (nicks, etc.).
 
My left tank drain and fuel cap on the Maule has been freezing up all winter, figured it s condensation from warm fuel being pushed in from the injector pump return. When things get warm enough I drain it and there’s usually just a trace of water. The other 4 drains are fine, It’s a pita and I keep a spare drain just Incase


Sent from my iPad using SuperCub.Org mobile app

It sounds to me as if you have some sort of problem in that left tank. I’d try to fix that.....”condensation” shouldn’t cause water in fuel, and the fact this is only happening in one tank is a clue as well.

Figure out what’s wrong with that tank and fix it before it bites you. Water in fuel is a very bad thing.

MTV
 
My left tank drain and fuel cap on the Maule has been freezing up all winter, figured it s condensation from warm fuel being pushed in from the injector pump return. When things get warm enough I drain it and there’s usually just a trace of water. The other 4 drains are fine, It’s a pita and I keep a spare drain just Incase


Sent from my iPad using SuperCub.Org mobile app

I forget what a maule fuel tank looks like. But if was a cub style one I bet your filler neck is cracking at joint to tank. Atlee dodge sells a rivet on replacement kit.


Sent from my iPhone using SuperCub.Org mobile app
 
IThe tank was out a couple months ago and was checked for leaks. Found a bad hose that was causing fuel smells in cabin. The fuel system on the m4 210 allows warm fuel to circulate from the header tank to the left wing tank and the vapor return eventually vents into it also. The fuel cap always has frost or some sort of condensation, the most water I’ve ever drained out of it probably wouldn’t have filled a 22 shell but just enough to freeze the sump. I’m guessing it just the nature of the beast


Sent from my iPad using SuperCub.Org
 
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One thing I have found over the years is timidity in draining causes leaks. Especially with probe type drains. Open that drain wide open and get a full and swift flow out it. That way, any crud sitting around the O-ring gets flushed out. If you don't do that, I find for instance on the Cub with the venting caps even little bits of insects collect and can cause leakage. Open the drain wide open and let it all flush past the O-ring.
 
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