Tuning Diana Bandit Fill Question

I just received my Diana Bandit and hand pump. I read everything and it shows to put the fill part inside the hole just behind the fill gauge. I insert it and start to pump and as soon as there is a bit of pressure, I cannot pump anymore and the port pops out the fill hole. I'm not explaining this very well, but it seems like the air isn't going into the pistol. Thanks
 
Usually when a fill probe wants to eject, it’s because one of the O-rings is sealing and the other one is not. Wipe them clean and check them with a loupe for any debris or a bite taken out of the perimeter. Check the inside of the port in the gun as well for any debris or scratches or gouges that could be interfering with the ability of the O-rings to seal.

If all looks okay, lubricate the O-rings with silicone grease or silicone oil and try again.

If it continues to eject, I’d be inclined to try new O-rings in case the originals have an imperceptible flaw.

Another thing to check is that the probe isn’t seating too deeply (or too shallow) such that the outboard O-ring (or inboard one) isn’t staying completely captured inside the port as you begin pumping.
 
Had a similar problem. Had to replace o-rings on fill probe and it worked? I have no idea why that would make any difference but it did. I love the bandit but I do fi d that it’s a bit finicky. I did put a regulator in and it helped. It’s a very accurate gun, especially for the price but you definitely get what you pay for. That said, it’s a great little gun. No complaints for the price at all! If I was comparing it to a $1000+ pistol it would be different but it’s a sub $200 gun and it is so much fun!!