I have 2000 f350 deisel dump truck and my bed wont raise

Can you see the PTO shaft spinning to pump? If it is spinning when you engage PTO, check hydraulic fluid. If you have good torque to pump and hydraulic fluid is up, you may need a pump. But they are expensive. Very. Before buying one, get a tester from a bearing and industrial hose place, the have them that you can take off the high-pressure hose from pump, put in-line from pump to hose. Should have up to 2000 psi. If you have pressure, next is hydraulic ram. The seals.