Originally Posted by bjr_93tz
You hit the nail on the head Ken, it's just there to stop fuel falling out when the vent is lower than the fuel level.
Agreed, in a perfect world this shouldn't happen when your engine is sucking on the other line, however I'm going to stick my neck out and say that the air pressure in and round your tank (and vent exit point) can fluctuate depending on which way your plane is pointing relative to the wind and how fast it's going, so it might not always be the case that the pressure in the tank is lower than the pressure at the vent exit point.
Well..... Because I do everything the hard way...... I'm going to run a vent line so it exits outside the fuse and deal with the consequences later.
It takes a bit of "pressure" or in this case suction to open that valve. In my own mind I feel I need to eliminate complexity. In this case it puts an extra load on the fuel pump. I can always put the check back in the line.
PS. 100 of you can tell me NOT to do something but because I'm a stubborn old fart I'll still try it