fly boy2

I had done an inspection of my tank and found no leaks. So the day after I ran a full tank of fuel and no problems. Today I did a taxi test and after engine quit after a fuel tank; I found fuel coming out the back of my spad deboniar. I'm pretty close to putting a new tank that I bought for another plane and getting fuel lines from my jug and pump. I did enlarge the holes that the lines come out of; I guess we'll see if that did it. I tried to look for a hole in the lines; and found nothin. any suggestion on what it could be.

w8ye

My Feedback: (16)

loose cap?

Crash Campbell

or maybe a split seam or pin hole in the tank that only appears under pressure? Did you submerge the tank in water, pressurise with a bicycle pump and check for a stream of minute air bubbles?

Cheers,

Colin

fly boy2

Am I suppose to be able to pull it out without unscrewing the little screw

Steve Steinbring

Pull the tank and lines from the airplane. Seal off all but one line, then pressure test the setup with air by submerging in water. If you see bubbles you've got leak, just follow them to the source of the problem.

fly boy2

no but I'll try that; the way I checked for leaks first time was to fill with water and look for leaks

Gray Beard

My Feedback: (-1)

Pressure test under water. I just hold it under with the lines pinched off except for the one, I use a long piece of fuel line on the open end and just blow into the line real hard and hold it while I look for leaks. I sometimes use a retract air pump but that is over kill most the time except for my YS engine takns.

Crash Campbell

NO

Cheers,

Colin

LuftwaffeOberst

If you can then there's your probem! Tighten that screw real good, then do the under water test that Grey Beard wrote about. Let us know if the plane leakes fuel again or not, then we'll take it from there.

jetmech05

be careful not to over tighten the bung (yes that's its real name) or you'll split the tank at the neck...never ever fill the tank with water....hard enough to get the water out, and water is your enemy....

CGRetired

My Feedback: (1)

NO! Don't "tighten that screw real good". It should be snug, but not as tight as you can get it. Doing that will split the neck of most fuel tanks.

I've read that the best method is to put the thing together, then turn the compressing screw in until it begins... BEGINS... to compress and seal the bung in the neck of the tank. It should be snug, but not tight. It should turn slightly, under pressure from twisting by your fingers, but that's just about it. Any more and it will more than likely split the neck of the fuel tank.

I will find the link that describes this to prevent what I expect to be some incoming flack about this. But, I think many of the experts here on RCU will verify that it should not be tightened beyond being snug, enough to slighly expand the bung and seal off the tank, but not tight enough so you cannot turn the bung in the neck. As I said, snug, but not turn easily, but turn with a little effort. How much is that? I don't know, but I do know it should not be so tight that it will not turn.

CGr.

MinnFlyer

My Feedback: (4)

True. It should be snug enough that you can't move it, but not too tight.

Gray Beard

My Feedback: (-1)

I think I read what CG just said but I still tighten mine until I can't twist the bung. I have never split a tank but I have stripped more then one of the plastic backers. After you assemble a few you will get the feel for it.

LuftwaffeOberst

60+ planes built, I still have yet to split a tank. Unless you are a over grown gorilla, it takes effort to split a tank. One turn after snug is perfect. "So tighten it real good" still stands.

bingo field

http://www.rcuniverse.com/magazine/a...rticle_id=1068

Minn's article on "Let's Talk Tanks"

fly boy2

yeah I found that out. ok I have some results and I found that I'm only leaking out the hole where the fuel dot line should be. Is this suppose to happen. I thought I could pull the bung off and could not;but I did twist is with very little effort. I dont know if this helps or not

LuftwaffeOberst

No... I would replace the line, use a safety razor and try to make a straight cut when you cut your new fuel line. Once you've replaced the fuel line push the male end of the plug in and see what happens. The Plug should be snug in your fuel line. If it leaks at the plug, I would use a fater male plug.

When you bought your plug, I'm sure it came in different sizes? Use a thicker male end Plug and change that part of the fuel line and see what happens.

I've had problems with plugs leaking in the past... after a while the fuel line weakens (from pluging and unplugging) resulting in leaks.

I use Kwik-Fill, they seem to be better. It just takes a bit of maintenance if I store my plane for a while. I have to squirt After Run Oil or Castor Oil in the Kwik Fill to keep the spring and gasket from sticking.

http://www3.towerhobbies.com/cgi-bin...&I=LXD745&P=ML

http://www.horizonhobby.com/Products...?ProdID=DUB334

Hope that fixes you problem.

brett65

My Feedback: (18)

This is why I use hayes tanks, now screw or seem to split or screw to come loose. The problem comes when you want to defuel a plane with a cowl, then you have to use one of those external bypass things from World Models.

Campgems

If you use a Sullivan or Dubro, or Hayes tanks overtightening isn't really a problem. Where it comes into play is the sub-standard ARF tanks. You want the bung tight enough that the tubing doesn't move easily, and that you can't pull the bung out of the tank by hand.

There is very little pressure or vaccum on the fuel system. Any thing you can do with your lungs to induce a leak should be fixed, but more that that, I wouldn't worry about. The most likely culpurt in fuel tank air leaks is the clunk to brass tubing line. Some of the flexable tubing that is supplied with tanks today are not very reliable.

The two fuel tank problems I've had in the last four years are both related to ARF tanks. One split after over 100 flights, and on the other, the flexable line to the clunk broke in half. Once I have set up a Dubro or Sulivan tank, I've not had any problems with it.

Just make sure that the ends of the brass tubing are not sharp. Use a fine file and cut the sharp edge off first. Clean any filings out of the tubing and the assemble the tank.

Don

jetmech05

If your leaking fuel out of the bung where the fill line is...then you need a new bung...might as well get a new tank...gotta be careful inserting brass lines in the bung...make sure they don't have a burr on them that would enlarge the hole and cause a leak....

MinnFlyer

My Feedback: (4)

Are you saying that the thrid hole in the bung was once opened (They are closed when new) but there is not a brass tube in it? If so, that's the problem.

You can replace the bung, or you could just stick a piece of 1/8" solid rod in that hole (Or a piece of brass tube that has been soldered closed)

TedMo

having read all the replies to your problem all contain answers for you. If you follow their advice and still have any problem throw the whole tank etc. away and get new. Be sure to follow the advice given.

k3 valley flyer

My Feedback: (18)

I pitch any tank with bungs and screws and brass tubes! Buy a Hayes tank and none of these issues.

fly boy2

I finally found the problem. The screw wasnt on tight enough[:@]. After tightning the screw I put the tank under some water and pressurized the tank with my lungs and no bubbles[8D]. I cant believe all the trouble over a loose screw; I learned my lesson. Hopefully I get to fly sun.. Thanks Ya'll

LuftwaffeOberst

Wahooo! You see, it's the little things that cause the most problems, WE are glad your issue with the leak is now fixed.

Keep the wings level,