I have a 1993 chevy silverado and i'm having troubles with the power stearing. when i turn the wheels the lines move like the pump is trying to pump but it doesnt make turning the wheels any easier an every once in awhile when i first start it the wheels move freely until the vehicle gets warmed up..
Probably a bad power steering rack. What color is the fluid?
Get under the truck, disconnect the return line and put a pan under it. Pull the fuel pump fuse or the ignition coil wire so the truck won't start and crank it for a couple of seconds. If black gunk comes out, you have a bad rack. DON'T run the pump dry!
Check the rack mounting bolts. If one or more are loose, it can cause the problem you describe, but unless the pump itself is leaking, it is almost always a bad rack.