I'm dealing with a gear retraction problem on PA28-201. The gear will not retract, just starts by braking main gear locks and then nothing more. To me it looks like the system is not building up pressure. I did install a new hydro pump e had but no change, replaced all hydraulic in the system etc. No luck so far, anyone had this encouter that could save me time. I'm thinking free fall switch problem as it could be stuck open not allow prssure build up. Note that the aircraft had been standing o ground for 12 months.