gas leak on migatronic

[stinkbridgenine]

i`ve got a migatronic rally 166, not really sure of the age but i think it`s quite old. i bought it second hand,and it seemed to work ok. now the thing is i`ve got a trailer that i need to modify so i thought that i`d renew the liner,tip and shroud before i started the job but i`ve hit upon a slight problem,which is,when i pull the trigger and the gas starts to flow,there seems to be more gas going inside the machine than down to the torch which sounds fairly straightforward to sort out. the welder has an internal gas valve which is at the `gas bottle end` of the machine and the leak seems to be from around the area where the torch lead connects to the machine. anyone familiar with this machine will probably know that there are `o` rings on the end of the lead, which i`ve renewed. i`ve added a few pics to show the torch setup, now it may sound like a daft question,but what stops the gas going `backwards` ie into the machine instead of down the lead ??
i`ve tried it with the gas pipe disconnected from the `torch mount block?` and blocked the end and when powered up, ie gas flowing, the pipe holds gas with no leakage.
has anyone had this problem before or could anyone give me any tips on what i may be doing wrong?
sorry if the pics are a bit poor/too big,but this posting pics thing is very new to me.

 

[shenion]

That looks very similar to a Tweco gun. On those, the last foot or so of the wire liner has a plastic sleeve like heat shrink over it to keep the gas from leaking back through the liner.

You said you "renewed" the o-rings. I replaced mine a few times. I found it was very specific on the size or it leaked at where the gas is fed into the torch.

 

[Jake SS]

The gun end looks dodgy to me, the 2 O'rings should seal in the housing and the gas should only be able to flow into the holes between the 2 o'rings, and hence through the gun

Cheers
Jake

 

[stinkbridgenine]

thanks for the replies chaps.
shenion,what you say sounds about right regarding the sleeve on the liner,although there was nothing on the old liner so i just replaced `like for like`.maybe the last owner just lived with it,but i can`t say that i heard it leaking before,although the side covers were on before i decided to renew the liner. does anyone know if i`d be able to buy this sleeve on it`s own or is it a specific liner,meaning that i`ve bought the wrong one? (which was a murex)

 

[shenion]

On mine the sleeve looks like regular heat shrink tubing.