I have 3 opening in my fuel tank. "A" is to the carb. "B" is for fueling. "C" is for Vent (from the muffler). I pumped fuel into "B" and filled the tank. Started engine and runs fine. After flight I had half a tank and so I tried to pump fuel out from "B". No fuel returns from the tank. the hand pump turns freely. If I turn the pump crank the other way( which is to pump) it starts pumping fuel. I tried pumping fuel out from "C" and nothing. So, I had to remove the cowl and connected the fuel pump to "A" and fuel starts pumping out. I must be missing something. what am I doing wrong? I have the same set up for all my other stuff and I'm not having this problem.

I can drain the tank from "A" so the there must be a clunk at that end - plus I label the openings on the tank. "C" the vent is bent up. "B" I have the tubing pointing straight in the tank. I havce a filter on the "B" fueling line. I tried with throttle open - and nothing. I tried pinching the "C" vent from muffler and nothing. And I'm still trying to remove fuel thru the "B" fueling line.

What's happening is that the 3rd line just goes into the tank and when you fuel it will fill the tank. But when you try to pump the fuel out that line is not submersed in the fuel, so it can't pump out the fuel.

For the fill line in a 3 line tank setup you need to do one of 2 things in order to defuel the tank through that line. 1) Inside the tank put a second fuel line with a clunk that will keep the line in the fuel.  or 2) run fuel tubing in through the stopper and then bend it down so that the tubing points to the bottom of the tank. Then to defuel the tank you can lift the tail of the plane and pump out the fuel. Either method words well. I prefer using #2.

Hope this helps

Ken

Oh my gosh - I want to say - "I knew that". Thanks a million.