Paul,

Get yourself a can of silicone spray lubricant. Carefully spray some into a cup. Attach a short piece of hose to the cylinder nipple closest to the shaft, extend the shaft, put the end of the hose into the liquid and push in the shaft to draw some liquid into the cylinder. Let the liquid sit in the cylinder overnight then exercise it a few times. The silicone causes the o-rings to swell and seal better.

My FEJ cylinders leaked where the shaft exits the cylinder. The above did the trick and they now hold air just fine. I also put some silicone lube in my retract cylinders for insurance.

Joe