Diaphragms have swelled and won't open/close...I've already disassembled and cleaned them. Looking for the model number of the valves to source repair parts, if available.
Thanks, Gator Guy, but I don't think that's it. This one doesn't have a flow control, just a bleeder with steel rod extending from the bleeder screw. I think these are at least 10 years old, if that helps.