Fuel coming out of fuel vent

Hello All,
I think I have finally figured out my fuel coming out of the vent.
On my airplane the vent is above the cabin on the left side (unlike the newer models behind the left strut) During my recent annual I found one of the vent hoses a little ratty looking and decided to change them. In doing so I paid more attention to the hole that has been drilled in the back side of the vent tube.I assume that someone did this as a safety in case of something blocking the vent. This hole is roughly a 1/4" in diam so it is substantial and is positioned just slightly below the front of the vent tube. It occurred to me that during flight with the tanks really stuffed with fuel that the air coming in the front of the vent and out the back through the hole there would be a vacuum created drawing fuel from the tank. I have temporarily taped the hole closed and the problem appears to have gone away. It may be too early to say for sure but I flew the airplane today with the tanks stuffed and no fuel escaped so I will watch it for a while to be sure. I'm not convinced the "safety hole" is required but even if I were to decide to keep the idea I think if the hole was smaller and re-positioned it might be OK.
Brian
My mind doesn't just wander.........sometimes it bugger off completely :))
 
I have a problem with fuel coming out of the vent on my 65 Citabria with 18 gallon tanks. The pictures were taken after an hour of flying. I have one fuel gauge only. It was at 3/4 at takeoff and about 5/8 at landing. I never top off since 36 gallons is really too much weight for an O-200 Citabria. The problem pretty much goes away when the fuel level is less than half. I am running nonethanol motogas but also had the problem on 100LL. The 100LL stains less, but the problem was still there.

I noticed my vent is much shorter than some others I have seen in pictures. Do I need a taller vent? I really hope I don't have a hole in the top of my tank as described above.

Any ideas? Things to check?

Thanks!
Rob
 
Robert, looking at your photo, it seems no wonder you have fuel siphoning out the vent. The top of the vent can't be much higher than the outer edge of the tank top when considering the wing dihedral.

I would make a new vent tube of the proper height.
 
I think mine sticks up out of the fairing at least 4".

I can measure mine when I go out the the airport tomorrow. I'll send an e-mail.

Dale
 
Robert, I sent an e-mail, but to share here, my fuel vent sticks up 3 3/4" above the fairing to the top of the tube.

I have no indications of any leaking from it.

Dale
 
Right, I just zoomed in on his being a 1970 as well, with the square 19.5 gallon tanks... my GCBC has the left wing vent however... seemed odd that his has the old style.
 
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