i have a d100 -  31p677-0236-G1.  2010 model .    I am assuming a line or pickup tube is stopped up.  before i start blowing air and possibly mess something up,  I was wondering what the smaller gas line coming out of the tank is for.  I have read fuel return line on some models , or vent line on others.  I am used to my older 2005 la115,  which is simple one gas line with a vent hole in the center of the cap.  fuel shutoff is ok on bottom of carb.  changed out fuel pump.