Anyone know anything about mig welder machines?

[robbocop33]

I've finding this really annoying and i cant get on with my restoration.For some reason the gas was reaching the gun fine,but where the white plastic liner goes into the metal block in the gun the gas was just coming back out??Instead of going up the swan neck to the tip?
After much swearing and blowing compressed in a reverse direction through the gun nothing improved.I then said sod it and ordered a complete new gun,shoved the white gas liner into the push fit connector at the gun,switched the gas on and it's still doing it!!!Aaaaaaaahhhhh!!!
What's going on?The little connector the gas line goes into in the gun has a death grip on the liner,you just cant pull the gas line out no matter how much you pull,so it cant be leaking,anyone any ideas?
Heres a pic of the white gas tube and the connector where the gas is coming back out of.

[227bhp]

http://www.mig-welding.co.uk/forum/