I love my Silca Super Pista pump. It recently stopped holding pressure so I took it apart and discovered the leather plunger cup had deformed on one side. Also the original plastic washer had cracked, probably causing the failure . I got a new metal washer the same size from my toolbox , threaded on the new leather plunger, greased it up, bolted it back on and I'm back in business. I love things that are rebuildable and come out as good as new!
Note: This is the 28mm diameter size for use with pumps with steel barrels 2008 and older. You will need to use the 30mm size for aluminum barrel pumps 2009 and newer. To tell which one you have, just get a magnet and if it sticks, it's steel.