The valve should have a 12mm nut on it,
it should only be lightly tightend, IT SHOULD NOT BE TIGHTEND TILL IT STOPS.
if you try to do this, you will damage the rubber bladder inside the fork, and it will no longer hold Air.
this rubber bladder is what holds the air, which helps stop the fork bottoming out, once that bladder is pierced your fork will just blow through it's travel to bottom out on the smallest bumps.
by the sounds of your post I'd say you have already damaged the bladder, the nut should ONLY be tightend enough to allow there to be no forward back slop on the valve, and enough so the Shock pump can be fitted to the thread enough to allow a seal for pressurisation.
Juls
