If you haven't already, check that the metal nipple coming off the tank is secured properly. I have had mine come loose.
Pull the pressure line off from the exhaust pipe. Make sure it's clean, then gently blow on the line at first. You should immediately see fuel flow. If not, blow a little harder. If still nothing then it sounds like you've got a pressure leak. Check the condition of the seal on the fuel tank lid. When you blow, can you hear escaping air?
It's mine: http://au.youtube.com/watch?v=usYhSWbmx6s