Wing tank not draining!!

[M Jones]

This subject has come up now and then, but I'm having some problems getting my wing tank to drain (right side available only). I'm going to take it in to my A&P when I can later this week, but was looking for some suggestions because he's not especially Taylorcraft literate, although he's got plenty of Aeronca, J-3, etc. experience...

I've determined that:
A) The old "push/pull" fuel valve works.
B) If I blow through the open valve to the tank (empty) with the cap on, I get some back pressure.
C) If I blow through the open valve to the tank (empty) with the cap off, I get no backpressure.
D) If I blow through the tubing that connects the header tank to the valve fitting, I have air movement to the header tank.
E) Wings level in the air with valve open, fuel does not drain to the header tank!!!
F) Wings level on the ground and opening the valve, fuel does not drain to the header tank!!!
G) The gas cap vent tube is not clogged because I can blow air through it, although there is some pressure.
H) I'm out of ideas, and I need it to get to La Grange in May!!!

This problem just popped up. I haven't had any troubles in the past. I think the line from the valve fitting to the header tank is kind of small (1/4") but it's always worked in the past.

Any ideas are appreciated!

[Howard Wilson]

Re: Wing tank not draining!!

Got to be a bug or crud in the wing tank to header line, or maybe a partially restricted cap vent, or worn gas cap seal leaking ram air pressure????

[M Jones]

Re: Wing tank not draining!!

or worn gas cap seal leaking ram air pressure????

Could be that Howard. I tried a different cap with the same results though. Maybe both have worn seals??

Thanks for the input,

[allen]

Re: Wing tank not draining!!

This same condition sometimes exists on my 1940 BC12-D. I find that if I put the airplane into a slight dive, while in flight, that the fuel will then start to flow from the wing tanks to the main tank. Just a thought; this works for me.

[Howard Wilson]

Re: Wing tank not draining!!

Mike, Could be that air will pass thru lines and valves, but fuel will not. The IA that I bought 20442 from said that he wasn't getting flow from the wing tank, so took off the wing root fuel valve and line from the tank fitting (wing to fuse) and with a wire pulled out tons of accumulated crud, just on the upside of the tank's fitting and the fuel valve. Since yours worked before then stopped working I'm still betting on partial restriction. With loose cap seal 2nd. Maybe our set-ups are different though?

[NC36454]

Re: Wing tank not draining!!

Mike,

Sounds as if your fuel is too thick! Seriously though, this is a mystery. I have the right side tank and mine will flow while sitting on the ground. Did you remove the fitting at the header tank and observe to see if fuel flows? Due to the radical bend at the wing tank fitting, fuel flow will be slower than you might expect.

Ken
1941 BC12-65

[lktiller]

Re: Wing tank not draining!!

I had one of the headliner bows crimp the tubing near the valve on the wing tank.

[M Jones]

Re: Wing tank not draining!!

Good suggestions guys, thanks and keep 'em coming if you think of anything.

We did remove the right angle fitting from the fuel valve at the wing root inside the cockpit while doing the ground test, and fuel drains into a can just fine when the valve is opened. Everything looks good there.

The fitting at the header tank is darn near impossible to get to, but that may something I'll have to get the A & P to look at.

NC22606 is bare bones, so it doesn't have a headliner, or anything that I can see that would cause a crimp in the line. I can see the line from the valve, to where it goes through the glare shield, and then from underneath all the way to the header tank. The only other idea I have for now is to have the 1/4" copper fuel line replaced from the valve to the header tank.

So two more questions then, is 1/4" copper the correct material and size, and does the gas cap at the wing tank need to be a "tight" seal to allow the ram air through the cap to do it's job?

I'm away for work until this weekend, so I won't be able to do much, but I'll make sure I post what the fix turns out to be. (I'm sure money will have something to do with it)

Thanks again!

[NC36454]

Re: Wing tank not draining!!

Mike,

The only way you're ever going to isolate this is to remove the connection at the header tank. After removal, use a container to test for fuel flow. This really isn't a big job, I just had mine off at the header tank a couple days ago. (Only took a few minutes to remove the connection)

I replaced my line from the wing to the header with SAE fuel line in the 80's and have never been questioned about it. I wouldn't worry too much about a tight (or loose) seal at the cap causing a problem. You should be able to get fuel flowing with only "ambient" pressure. If you can make it work on the ground, you should have no trouble in the air.

Hopefully, you can fix your problem without using that "money" you mention!

Good Luck,
Ken

[Howard Wilson]

Re: Wing tank not draining!!

Before I built the ram air cap for 20442. I didn't worry too much about the non standard cap that was on the plane when I bought it, after all the fuel transfered on each leg of the 1100mile trip home. Sometimes had to do a whoopdeedoo to get it going but it worked. Then one day I counted on it when a line of thunder storms beat me to my destination by about 5 minutes and my two alternate airports at high elevations were socked in by lowering clouds, so turned on the tank to give me enough gas to run back to Cumberland MD..... and that sucker wouldn't feed. How come the farmers leave big old hay bales in the best landing fields?? Haven't had a problem since, Don't even have to do whoopdeedoos except for fun. If it's marginal somethings wrong, That wire starts right up within just a minute of turning the valve.

[VictorBravo]

Re: Wing tank not draining!!

I just had a similar problem in N29544. There was no obvious clog in any of the lines, but on the FIRST ferry flight the fuel did not feed from the aux tank. On the second landing I bounced and had to go full forward on the yoke for a moment, and from then on the tank fed.

However I didn't take any chances. I had a friend braze a copper tube into the fuel cap and bent it forward like a pitot tube.

One of my thoughts was that even though the cap was a vented type, the low pressure on top of the wing did not allow it to vent properly. this would never happen on the ground, but flying at 90 mph you have a considerable low pressure zone above that fuel cap. So I decided to make it a positive vent, and put in the ram air tube. The opening of the ram air tube is 3 inches above the cap and a couple inches forward.

Haven't had any problems since.

Bill

[M Jones]

Re: Wing tank not draining!!

I'll be having a better look at the line this weekend I hope Ken. I can't see any way at this point with everyone's comments that the 1/4" feed line isn't partially restricted. What's really got me confused is that I blew the line out from the valve fitting to the header tank with about 40 PSI. I didn't have the fitting at the header tank off though. (Empty header tank by the way!) I did a couple of stalls with it last Saturday and Sunday, and about 15 landings by the way. That didn't help to get the fuel flowing either.

I do have a "ram air" cap on the wing tank too, and it seems to be OK...

Thanks all,

[M Jones]

Re: Wing tank not draining!!

Just for the record, I got out this weekend and figured out what the culprit(s) was. I used plural culprit because I had two wing tank caps with bad seals. Howard, you were right on thinking originally it was bad seals, thanks! One had a couple of cork seals in it that were too small, and dried out too. The one that is normally on the right wing tank and worked before must have just gotten to the point where the seal wasn't doing the job. I thought earlier that the tank wasn't draining with wings level even on the ground, but found out Saturday that it was. Must have been all the Stearman noises at the field the day I couldn't hear the fuel draining to the header. The fuel drain to the header tank sound was obvious this time.

I picked up some new seals at my local "aviation hardware store", and now life is good. Well, better anyway. Had a heck of a time trying to taxi back to my hangar on the north end of the field from the east/west strip. Wind was pretty gusty and strong out of the WSW. I really need to get those new brake linings on...

Thanks again.

[Howard Wilson]

Re: Wing tank not draining!!

Mike, Glad you found it. Beats finding the problem in the air!:-0