Sounds like the priority valve on the hydraulic pump the spool is sticking(stuck open)....should have 150 PSI for the load sensing sytem to open the spool for oil flow to the steer orbitol.....following is for the sytem

The steering system is a load sensing closed center type and uses hydraulic oil for its operation. Oil flow through the steering system is closed unless the steering wheel is turned. The flow through the steering gear is sensed by the priority valve, which then allows additional oil flow to the steering system. The priority valve also fills the requirements of the power brakes (if equipped) and then the mast.

Hydraulic oil is pulled from hydraulic tank (17) through a strainer to hydraulic pump (16). The pump sends the oil through hose (7) to brake valve (3). When the steering gear and brake valve are in NEUTRAL position, pressure in hose (15) and the priority valve internal sensing line rises to 1035 kPa (150 psi). When this pressure is at least 1035 kPa (150 psi) more than load sensing signal hose (12) the priority valve metering spool shifts to stop oil flow to the steer gear.