Hi all; I'm new here, so bear with me. I bought a used, but very heavy duty log splitter last year - got it home and waited a few months to use it as I bought it during the Summer. Guess what it was not able to split any log over 8". So I tore it down and replaced many parts, the pump with a 3500 psi model, a new valve for the same, and had the 5 1/4" piston checked in a certified shop. The piston checked out fine. I reassembled it and replaced a few of the hoses, flushed the lines, filled the hydraullic tank, and started it up. Started up and ran fine which is a plus. Its a 12 h.p. engine. The problem I'm having is odd, apparently the ram will retract fine when the engine is started, but it will not push forward at all now when running. There is no binding on the beam at all. It operates very smoothly when it does operate. If I reverse the lines on A and B, the ram will extend to the max, but will not retract. I have no detent adjustment on the valve. The valve was purchased from Northern Tool, made in USA. It was supposed to be a detent valve and when you engage the pump by pushing the lever forward, to push the piston forward, you can hear the pump strain but nothing happens. The valve can then be snapped backwards but there is no "auto return". At this point I'm at a loss as to why I can't get the darned thing working. I have wood to split! Anyone have any ideas what to check? I've nearly replaced the whole thing other than the wedge and the I beam. *update* OK, basic question here. I have a double acting cylinder (Piston) on it - its massive. I bought a single action valve from Northern Tool basically because I didn't know any better....is this the reason why if I change the lines on A and B I get the same results but in different directions? I need it to push/pull, not push, or just pull. Can I use a single acting valve on this at all?