[encantotom]

when the tank is totally empty, i would take the screws out of the top and take the entire interior assembly out.

if it is sticking it is one of two things. the first being the unit itself. it can be easily rebuilt and i have done several. you can try the thing when it is not installed (except for air) and see if it moves freely. the paddle that is on the unit often gets distorted and wont go into the slot that is on the bottom of the body of the fitting that is glued in.

if it is old, i would probably replace it if it looks distorted at all.

the second is if there is debris in the bottom of that valve body in the slot, making it hard for the paddle to go down in there.

i use a boroscope to see down in there or take a picture with your phone. then you can take a long flat screwdriver and gently clean that slot out.

parts have been avail in the past and i always keeps spare paddle, paddle assembly and cylinder rebuild kit.

tom