Hydraulic system operation should be instant and smooth. For every pump stroke, the cylinder should rise evenly. If the cylinder movement is erratic or jerky, there may be air in the system.

Air will always go to the highest point in the system; this includes the inside of the cylinder plunger. That is why the cylinder must be turned upside down (single-acting) or laid on its side (double-acting) to get the air out. To remove air from the system, position set-up as illustrated.
(NOTE: double-acting cylinders must have the couplers facing up.)
Fully advance and retract the cylinder two or three times. You can usually hear the air escaping through the reservoir.