I'm working on a cat m50d. serl.6GC02632. power steering won't come on? i unhooked the orbital pressure switch nothing. when the key is turned on primary contactor engages. sitting on seat. move direction control fwd or reverse accelerate still no power steering. pump never comes on. when lift.tilt.S/S. lever is used the function selected works and power steering also works. release lever steering stops. if i'm not mistaken isn't the directional lever what turns on the pump for steering. other than steering problem truck operates as it should. any ideas would be greatly appreciated.