Just finished installing a hydraulic thumb but I can only get it to move one way. I can't find anything in my op manual about selecting single or two way functions. I just find a bypass selector valve which routes oil through a secondary filter for single way breaker operations. I have this valve set for normal two way operations. I can get it to extend, but not retract. The extension side is the way it would work in a single way setup. I can not crowd it with the bucket and overcome the thumb so I know I need to adjust my pressure relief. However, if I hold the pedal and try to retract the thumb while crowding with the bucket it will move. But it won't stay there. The thumb cylinder was empty when I hooked it up. Do I need to bleed air somewhere? I am used to my tractors and I just flow oil one way until the air has moved back to the tank. I closed it when I first tried it and held flow to it for 30sec or so. Or did I miss a valve or switch somewhere to make it two way?
you need two lines to make it double acting, one to push the cylinder out, and one to push the cylinder back in. If you only have one line it will never be double acting.
Did you ever figure out your problem?