Well, almost.  But at least I figured out how to get gas out of it.  
When I ran out of gas and as I investigated and emptied the fuel lines too and seen the tank not wanting to let any gas out somehow, I even changed the tank.
But all the thinking and wanting to know have resulted in success.
I have had to prime the pump and fill the hoses with gas to be able to have enough suction that would make continuos flow.  
There has to be some kind of valve that will just stop the gas from flowing out, but it would let go once the pump is primed.  
I hope it helps for some of you.
Zoltan