Hey buddy, I had the EXACT same problem, and here's the answer that fixed my issue as quoted from Bill the PE tech here on the nation:
(It turns out that my Ego didn't like my brand new CVS brand 9v and would only accept a brand new Duracell brand battery and then worked fine....picky little b*tch. Pretty...but picky.)
- Try a new Energy, Duracell or Energizer battery. The gun needs a good amount of power to run the marker properly. A lessor brand of battery may read fully charged but doesn't have the upkeep to sustain the power needed to run the gun. This is the #1 cause of all issues in an EGO.
- Replace the #11 rammer oring. Even if it looks good. It will be the largest black oring towards the rear of the rammer.
- Set your dwell (14.0).
- QEV Diaphragm issue. Inside the QEV, between the blue and silver halves, is a rubber diaphragm. This part should be one piece. Make sure it is not ripped or cut (see page 63 in the manual).
- Check the HPR. Make sure it is assembled, lubed. Make sure there are 16 shim springs properly assembled. The shims are slightly bent. You want them opposing each other. )()()()()()()()(
- While you have the HPR apart, check the HPR Piston reg seat. Make sure it is there and not cracked (See page 44/45 of the manual). Perfect preesure would be 325 psi. It can be achieved by properly assembling it then spinning the adjuster screw all the way out and then 3.5 turns in. This will give you the approximte pressure.
- Check the LPR. Make sure both springs are present. There should be 5 pieces within the LPR. Starting from front: Adjuster screw, Adjuster piston, gold spring, Regulator piston and second gold spring. Both springs are the same. Put the adjuster screw flush to one turn out, see if this affects the velocity at all.
- While you have the LPR apart check the LPR piston seat. Looks just like the HPR piston but smaller. Seat is in the same area...
- ASA On/Off knob turned in to far? When you add your air system to the gun you want to turn the knob until you hear the initial gas transfer. Do not turn it more then one complete turn more or you will actually restrict the airflow coming out of your air system.
- Complete oring overhaul