All I have to offer is how I got mine working again, it was leaking air. I removed the compressed inlet line and added a couple drops of air tool oil. after working it a few times it began operating properly-stopped leaking.
The "O" rings get too dry to slide properly is my conclusion. DO NOT use ordinary oil, additives may cause the "O" rings to swell.
2000 Winnebago Ultimate Freedom USQ40JD,
ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG 11B5MX,Infantry retired;Good Sam Life member,FMCA." My fellow Americans, ask not what your country can do for you, ask what you can do for your country. John F. Kennedy