sounds like one of the FS Racing units. not seen much out on these yet as they are still pretty new to the market. i would imagine they are similar to the shocks your used to working with, just a bit bigger.
make sure all seals/orings are in good shape, ie, no cracks, gouges, and are plyable still and not getting hardened.
what i do is once i know all the componants are good and ready to use, i ll put them together, seating the bottom cap but not tightening it. then fill the shock from the top and seat and tighten the top cap up. then flip it over, pump the shaft a few times, you may need to re loosen the bottom cap a bit to do this. what your doing is working the air bubbles to the bottom cap (which is pointed up in the air now) then losen the bottom cap enough to allow the air and any extra oil to bleed out while you push the shock shaft into the body about 2/3rds the way. when you get the shaft in 2/3rds the way, tighten the bottom cap to seal the shock up and install the spring on the shock. it should compress fully and retract fully when not installed, it should also feel firm and not spongy or like the shock is filled with cottage cheese. if it feels like this, you stil have air in the shock. you ll need to add some more oil and rebleed until you have all the air out and the shock shaft feels smooth and steady as it enters and leaves the shock body.
hth
T