My son was nice enough to unscrew the pressure screw on my floor jack. It is circled in yellow. Under the set screw is a spring and a round ball. I put the ball in first then the spring back in and tightened the screw down, but I don’t have and can’t get any pressure to build back up in the jack. The jack will not even lift its arm by itself, let alone the weight of an axle. I also need to put the cover on the hydro-fluid reservoir. Can anyone explain how I can fix my floor jack so it can build up pressure? I figure it is like bleeding brakes, but don't know how to do it with a floor jack.