Is my compressor shot?

It should be easy to eliminate check valve/ unloader issue. With compressor cycled off, and disconnect "OFF" turn pulley. Should turn fairly easy with no or very little hint of compression and YOU SHOULD be able to hear air hiss out of the unloader as you turn it. Then with power back "ON" Pull relieve valve or "unleash" a blow gun, etc, until you bleed enough air that it starts. If it does not start or trips something you likely have a motor problem