Will not feed wire when trigger is pulled. feed

Metallic inert gas or mig welding for short - unless using flux cored welding wire, an inert gas is an essential part of the welding process.
The torch and tube assembly usually consists of a welding cable to carry the welding current to the wire tip of the torch, a wire liner through which the welding wire is delivered and a nylon tube through which the gas is delivered and a return wire from the trigger. The whole is encased in a single heavy duty tube.

I suppose the nipple could be the gas inlet - why not try it and see...

there is no seal at the feed rollers around the wire as it requires the correct gauge wire and feed hole to slow down the loss of gas at that point ( easier for the gas to escape up the wire housing and out the welding end )
the gas is allowed to flow when the welding trigger is operated as that opens a gas solenoid that allows gas to the welding wire tube to exit past the shroud around the welding point

read you user manual well to be acquainted with the machines operation, and if there is a persisting problem talk with your supplier and consider a warranty service check

The tip of the welder may need cleaned out, your feed speed might need slowed down, check the polarity is it straight or reverse?

check for circuit breaker by drive motor, it may be the pc board.

I have a clarke 85en no gas welder. the gun on this particular welder is always live the trigger only feeds the wire

trigger switch may be stuck on.

You could have a couple of things wrong. A bad trigger switch is very common. That is about 99% of the time. Next are connections to the box.Not too common but they can corrode or get loose. Then you can have drive motor issues or something annoying like a pinched or galled liner stopping the wire.

To rule out most things we need to know if the wire feeder is working or trying to. All we need to do is press the trigger and listen for the feeder motor. We want to do this with the top open so we can see it as well. If it doesn't do anything then we need to look at the switch, connections or the motor itself.

If it sounds/looks like it wants to work then we might have something simple like the wire drive or pickup being out of adjustment or worn or the wrong size or type for the wire you are using. If you lay the lines out straight and then try to manually move the wire it should be stiff but smooth. Use pliers at the pistol to pull on the wire, and loosen off the driver wheel tension. If the liner has a kink or was damaged then the wire will not feed or will be very hard to move.

My bet would be on the switch.

open the area were the role of wire is and check when trigger pulled if any action to feed motor. [wire might be stuck at end, or there usually is a small fuse in that area for feed motor]

Try to short the trigger wire back closer to the unit or better still inside the panel somewhere. There is often a relay that is operated that allows gas to flow and power to the wire feed motor. Check where the trigger wire goes it may give you some idea. If you can identify the part you can source one and see if it worthwile repairing. Cheers

If you use it regularly, the liner should be replaced about every 6 months. Make sure you get a wiper for the wire. It goes inside the machine, on the wire, just before the feed rollers. It keeps the dust from clogging the liner.