I've got a brand new Coleman Apex II and it won't stay lit. I have to pump it like mad and, believe it or not, wiggle the fuel bottle.
Pressure builds okay.
It sounds like too much air, not enough fuel. Flame fades with pressure, but if I wiggle the bottle before the pressure is gone, it kicks up. I can't find any leaks but haven't taken a wrench to it yet. Just for the heck of it, take everything apart, empty the fuel bottle, and start over. Certainly, it sounds as if pressurized air is hitting the nozzle, but not much fuel is coming along with it.