Weld problems

I've got a parweld xte171c and its been great for the past few years but I've noticed over the past couple of months this problem where I can get porosity in the welds sometimes but not others even when only minutes apart without changing settings.
Sometimes it won't happen and it will weld ok but others I cant get a weld without porosity ive attatched the settings ive used on these few test welds to show what happens. Any ideas? Thanks No porosity in these welds which i did first, then I did these.

 

looks like a gas problem (lack of gas)

 

Yeah it does look like a lack of gas problem ..was it a breeze in the workshop ?

 

No all doors are closed. Could it be something to do with torch or regulator.

 

is the problem always at the start of a run or not

 

Yest mostly and sometimes it stops and sometimes its for the whole weld.

 

could be the gas valve sticking

 

Is that in the welder or torch ? . I can hear gas come out of the torch when the trigger is pressed.

 

Gas solenoid inside the machine. Easy to take out, dismantle and clean. Crud can stick them both open and closed.

 

also could be a small gas leak in the pipe to the torch as you are losing gas at the start of a weld

 

I did upgrade my torch about 2 months ago but it did happen with the old torch aswell.

 

Check you gas flow from out of the gas shroud with a flow meter, you'll be needing a out 12/13 litres a minute for light sections, and going up to 18/19 LPM on heavier steel: I have welded in ship building and repair and have not been instructed to use any more, although there may well be people who have:
Your regulator is set to 10lpm, that's what's apparently going into the torch, this is an inadequately volume to start with, and may(probably) bear no similarity to what exhausting at the shroud end