Since the power steering is functioning and there isn't any unusual sounds like cavitation from the pump(Clogged filter) we can assume that we have sufficient pressure and flow.
View attachment POWER STEERING TUBES%2C 1910.pdf
Your hydraulic system uses a unloader valve (Part #1) to prioritize the flow into two separate systems. The first system is the steering and the second is every thing else or in your case the FEL and the TPH.
Your first test is to lift an object over 200Lbs with the FEL
If you can lift a heavy object proceed to Blockage.
If you cannot lift a heavy object proceed to Unloader valve and pressure relief.
Blockage:
If you can lift this object you have sufficient pressure but reduced flow.
Connect two pressure gages in line with the flow in front(pressure side) and behind(relief side) the FEL valve. While lifting the arms of the loader without a load there should be less than 250psi on the pressure side and less than 100Lbs on the relief side.
If your pressure is high on the relief side there is a blockage between the loader valve and the TPH valve or in the THP valve.
Unloader valve and pressure relief:
If you cannot lift the heavy object you have reduced pressure and flow.
1. Connect a flow gage to the steering relief port (Part #10). While lifting the arms of the FEL without a load there shouldn't be any oil flow on the steering relief.
If oil flows from the steering relief port while lifting the FEL your unloader valve is not operating correctly. Most likely a broken spring in the unloader valve.
If oil isn't flowing from the steering relief port while lifting the FEL then your pressure relief valve is not working.
Mike
