98 firing intermittently

a few suggestions:

1. make sure the ball detent isn't in backwards and there's nothing obstructing the movement of the bolt inside the breech
2. make sure the air or CO2 tank is filled completely
3. try putting a few drops of oil in the ASA, hooking up an air source, and dry fire 15-20 times without the barrel on, and see what happens. sometimes if the o-rings aren't properly lubricated, the gun won't function properly

If everything inside looks ok, you might want to check out the back of the powertube for deformities and the rear bolt's o-ring to make sure it isn't swollen or screwed up.

If no air is being released then the hammer is not striking the pin... something is obstructing the moving parts from moving all the way forward: the ball latch in backwards will hold up the front bolt, a deformed powertube opening would prevent the bolt form entering, and a screwed up rear bolt o-ring will also the rear bolt to hang up.