PMI Trracer powertube leak
I've been trying to fix up my old PMI trracer, and have ordered some parts for it from Bacci paintball which I just got today. I put in a whole new brass nut into my valve assembly, complete with cupseal and powertube. Everything looks like its in great shape, and the valve nut assembly was advertised as 'tested, no leaks'. I can't see any marks at all on the cup seal, looks new.
However, when I screw the valve assembly onto my HPA tank, it leaks out of the powertube. If I cover the powertube with my thumb, it gets much quieter but I can still hear a very slight leaking noise. I've tried putting in a heavier valve spring I had lying around inside to 'push' the cup seal against the seat a bit tighter with no luck.
Is it possible that the low pressure in my tank (its only somewhere between 100-500psi according to the gauge) could cause the cup seal not to seal properly?
I'm thinking teflon tape on the valve nut threads might help the quiet leak I hear when I cover the powertube. I'll try re-filling the tank and putting teflon tape on the nut threads. Is there anything else I can try, or easy to obtain parts from other guns that might make a good cupseal?