Had a system that wouldn't pump down last weekend. In the process of figuring out what was wrong, replaced the pistons/o-rings in my gauges and gaskets on my hoses. Then tried to pump down just the gauges and couldn't get below 3,000microns,then tested gauges against 350psi with leak check solution and found no leaks. Concluded that something in the pump needs rebuilt. Then pumped down gauges with different pump,went down to 200 and slowly climbed back up. Checked my 4 other sets, the same thing. ....any thoughts? and has anybody ever rebuilt their own pump?