Fuselage fuel tank / filler neck

[woodmw]

On bumpy days, even with only half fuel in fuselage tank, I have been getting a fuel smell. Thought it might be wing tank, but they haven't been used for a few months. I have never found liquid fuel dripping, just smell. I tried to wiggle the filler neck, and it moved. Doesn't seem to be solidly attached to tank. I plan to remove tank while plane is down for strut inspection.

Question:

How is filler neck attached to main fuel tank?

[M Towsley]

Re: Fuselage fuel tank / filler neck

Mike,

Can't help you with that particularly, but after it is fixed you may want one of these to help keep fuel out that does overflow, especially when filling the tank. Very nicely made, too. Link: http://vb.taylorcraft.org/showthread...t=neck+grommet

[Larry Lyons]

Re: Fuselage fuel tank / filler neck

If you have to remove the tank you will have to remove the engine as there are two rods that go through the middle of the tank, both about 30 inches long. Removing or installing the tank can be a bear even with an uncovered fuslage. Do a search you may find a thread here on removing it with out removing the engine but I believe it was a real chore. Having done it on a bare fuslage it was a bit tricky. Larry

[3Dreaming]

Re: Fuselage fuel tank / filler neck

If you have to remove the tank you will have to remove the engine as there are two rods that go through the middle of the tank, both about 30 inches long. Removing or installing the tank can be a bear even with an uncovered fuslage. Do a search you may find a thread here on removing it with out removing the engine but I believe it was a real chore. Having done it on a bare fuslage it was a bit tricky. Larry

I've done it a couple times and you don't have to remove the engine, but like Larry said it is a real bear. The "H" column has to be removed and lowered. The instrument panel also has to come loose and be raised to remove the rods. You also need long arms like a monkey to reach the nuts on the back to remove them. If the rods are stuck in the bushings then that can create a whole other set of problems.

[3Dreaming]

Re: Fuselage fuel tank / filler neck

On bumpy days, even with only half fuel in fuselage tank, I have been getting a fuel smell. Thought it might be wing tank, but they haven't been used for a few months. I have never found liquid fuel dripping, just smell. I tried to wiggle the filler neck, and it moved. Doesn't seem to be solidly attached to tank. I plan to remove tank while plane is down for strut inspection.

Question:

How is filler neck attached to main fuel tank?

It depends on what type of material your tank is made of. If it is aluminum with a steel filler neck they used a funny brazing solder type material.

[Hank Jarrett]

Re: Fuselage fuel tank / filler neck

As to your question on what holds YOUR filler neck on right now I would say,........probably.....Gravity. I have seen a few that were epoxied on, but that is a BAD idea. When I took my tanks out I was doing a rebuild so I took the windshield out and removed the engine and boot cowl. After that pulling the cross wires out of the tank was pretty easy. Actually, pulling the boot cowl was pretty easy anyway, and I got a whole BOX of fasteners from under the floor boards!
Hank

As well as coins, dead insects, candy wrappers, cigaret butts, costume jewelry and about 5# of unidentifiable debris. EVERYTHING dropped in the cockpit seems to end up between the boot and floor boards, and NONE of it was seen when the boards were pulled!

[Guest]

Re: Fuselage fuel tank / filler neck

It depends on what type of material your tank is made of. If it is aluminum with a steel filler neck they used a funny brazing solder type material.

Here is one of those funny solders

http://www.harrisproductsgroup.com/en/Products/Alloys/Soldering/Lead-Free-Solders/Al-Solder-500.aspx

[Richard Boyer]

Re: Fuselage fuel tank / filler neck

Another spot it can leak is at the bottom attach point. If the elbow where the fuel cutoff valve is overtightened it can cause seepage. The seepage wont drip, but will cause a fuel smell in the cockpit.

[astjp2]

Re: Fuselage fuel tank / filler neck

No you don't have to pull the engine, just the instrument panel. I just did one on a 46, you need to drop the panel, control column H assembley and disconnect the rudder pedals. Pull the rods and the tank drops out. All of this once the fuel lines are disconnected and control cables are out of the way. Then if its a turn plate tank, take it to a radiator shop and get them to resolder it. I would also get the lower bung reinforced where the valve attaches. Tim

If you have to remove the tank you will have to remove the engine as there are two rods that go through the middle of the tank, both about 30 inches long. Removing or installing the tank can be a bear even with an uncovered fuslage. Do a search you may find a thread here on removing it with out removing the engine but I believe it was a real chore. Having done it on a bare fuslage it was a bit tricky. Larry

[Ron Coleman]

Re: Fuselage fuel tank / filler neck

Before you pull the tank I would replace the fuel cap gasket, tape up the filler neck (or seal the filler neck grommet) and then pass a cotton string across the top of the tank to see if there is any residue goo stinking up the place. If so clean it up then go up and bounce the bird around a bit, if you still smell the gas, pull the tank.
RonC

[Hank Jarrett]

Re: Fuselage fuel tank / filler neck

An easy and very effective test is to unhook the fuel line from the carb or bowl, empty the tank, clean the filler neck well, and put a condom over the filler neck. Tape the condom in place so it doesn't blow off and have someone in the cockpit open the fuel valve while you blow into the fuel line and close it when you stop. A few good lung fulls and the condom will inflate. Shut the fuel valve and listen for the air escaping (I am betting there will be a lot around the filler neck). Try and not laugh while doing this because all of the ramp rats will be rolling on the tarmac. The sight of a full condom in front of the windshield is pretty funny, but the method is great for finding pin hole leaks in the fuel system. After I rebuilt my fuel system my plane would keep the condom full for over two hours. If it stays full over 4 hours call your IA immediately as permanent injury could result. ;-)
Seriously, my system actually stayed inflated much longer once I found a way to seal the filler cap on the wing tank. A little jar of soapy water and a brush to put around the threaded connections will bubble like mad if there is a bad seal. Make sure you take pictures. If I hadn't, my wife NEVER would have believed what I was buying condoms for and the folks at the drug store got a huge laugh out of it. You CAN use the cheapest condoms you can get (although he fancy ones would be funnier) and toy balloons don't work. If there is ANY fuel residue or oil that touches the condom it will tear or burst there so get the neck really clean and DON'T clean it with solvent.
Hank

Do NOT, EVER!!!! pressurize the fuel system with compressed air!!! It only takes a few pounds of pressure to do TERRIBLE damage to the tanks. No matter HOW good your regulator is, USE YOUR LUNGS AND A CONDOM! The condom will pop, or you will burst out laughing before you can damage the tank.