Gas Bottle Wood Burner

hi everyone ,,,this is my first attempt at a log burner ,,,, it seems to be OK so far, but i have few questions I'm hoping  one of you can answer

 as you can see in the pics i chosen to have my bottle on its side ,, and my door is bottom from second bottle .... the chimney is 4 inch in diameter and protrudes about half way into the bottle ,,, but has baffle plate in front of outlet on the inside .

my question is when i close the door the fire goes out  or dies to a point of going out  but burns fine with door open .....

the vents in the door are approx ,,, 1.1/2 inch with butterfly's but do not seem to flow enough air to keep fire going ..

can anyone shine any light on were I'm going wrong

thanks  Ian