If your Orion or Avenger does not work here are some good maintenece tips:

• Make sure all o-rings are not broken and oiled - this includes the ones on the valve (Orion as most BE and VL markers use universal o-ring size for all o-rings)
• A lot of leaks happen at the valve because either the cup seal is out of place, not oiled properly or similar reason, so oil the cup seal put some oil on the rings around the valve and put it back in. Remember use marker oil (ACI and Extreme Rage make it its about 4 dollars a bottle) if you really don't have it or can't get it then use good mineral oil (ky-gelly also works), regular real oil like the one for cars, wd40 or cooking oil will kill the rubber seals (so don't ever use it).
• Clear any dirt you see inside the marker (sometimes during long use the aluminum or steel will gently scrape on the inside of the marker and leave minature shavings)
• Unscrew the front low pressure chamber (the aluminum stud under the barrel) see if the spring holding the cup seal is not damaged or misaligned (this is also a way to see if the cup seal is ok without take the whole marker apart)
  -make sure all hoses are tightly screwed in ( well you have only one hose )

• if it is leaking at the bottom line or the duckbill where you screw in the tank then it could be bad pin on the tank or bad threading on the duckbill, check both.
• if it is leaking around where the hose connects to the marker then check the hose maybe its loose or broken inside
• if it is coming from the barrel and or the top ball feed then problem is around the valve, if you cock the marker then and its still coming for the barrel and the problem is definitely with the cup seal

Before you get discouraged and say BE and VL is crap, you have to understand that the marker which you bought was probably made some 4-5 years ago, and until it fell into your hands it was never used before and lead a shelf life, any seal and rubber o-ring is probably degraded by now and will need replacing, (e-bay has like 100 standard polyurethane rings for 5 bux its a good deal). Some parts say like the cup seal, trigger, shear could just get stuck from a long time of not moving. This is why some markers have problems out of the box. Recently I bought a brand new Rainmaker (it was made in June 1998) and never used since then, when i connected air to it I blew out 3 hoses, cracked 2 air fittings, and almost damaged the electronic control valve. Took me 3 weeks and 60 bux worth of replacement parts(its hard to get rainmaker parts since BE stopped production in 2001) to get it to shoot properly. But I didn't get discouraged cause I really wanted to play with it, and I also learned some usefull stuff.