I have been working on an airgun that was my great grandfathers (Benjamin 317). so far I have replaced the felts and changed out the pump cup for a synthetic one. my issue is I able to pump and get some pressure in the piston but for some reason the airgun wont actually pump up the air will just stay in the piston. so far I have tried an alcohol flush but the valve itself wont open up to let anything in. Im not to sure where to go from here whether that might be opening up the valve itself from the back or just trying the alcohol flush over and over again until it might work.
I am relatively new to airguns and I own the Benjamin and a Ruger uforce. I have experience maintaining and fixing paintball guns which are surprisingly similar with the hammer and valve system. Anywise help from a more experienced airgun owner or somebody that has worked with vintage airguns like this would be immensely helpful.