Millermatic 130 Xp Manual
The ball should only float when the trigger is pulled. I'm guessing that you don't see it float then, either.
Not sure about the welds being white. What material are you welding? Does the ball drop all the way back to the bottom? Or does it drop to a lower level and hover? If the flowmeter is opened up and there is still no gas, I'd guess that you have a stuck valve, or it's not getting voltage. If you had a leak inside the welder, you'd see the ball floating all the time.
Here's the manual for your welder. I haven't looked through it yet, but you may be able to trace some wiring to the valve and make sure it gets voltage. Welding galvanized metal will leave a white film. That's something to be careful of. The fumes are not good for you.
Millermatic 130 Parts Manual
Some say they're really bad, others say they're just bad. Either way, they're not good.
Better off finding bed frames or other mild steel scrap to practice on. Galvanized metal can play havoc with you trying to get a nice weld, too. I'm not sure I understood the part about closing the bottle and the gauge reading lower when you came back. A small amount of leakage is probably not a big deal. That still doesn't account for the lack of shielding gas when you are welding.
Have you tried adjusting up the flowmeter a little more? If you think the flowmeter is at fault, try this: 1. Close the bottle.
Disconnect the hose from the welder. Open the bottle. Check for gas flowing. You should see the ball float and also feel gas flowing. Adjust the flowmeter and see if you can adjust it so that there is only a little flowing and then adjust it up a little.
You should also see the ball move up as it is opened up more. If the flowmeter works like this, then the problem is in the welder. Just double-checking - do you hear or feel any gas coming from the gun when the trigger is pulled. You might also post some pics of your welds. That'll give us a better idea what you're seeing with your beads.