Log Splitter - Low Pressure

[Troy Field]

Hi. Recently my 3 year old log splitter, with approximately 100hrs on it, has lost almost all of its splitting pressure. When the problem began I noticed the control valve was leaking so I replaced it with an identical valve. The splitter didn't come equipped with a return line filter or pressure gauge so I installed a new filter between the valve and the oil tank and a new 4000psi gauge on the pump outlet. I also stripped the pump to look for signs of wear but everything looked clean and there were no obvious signs of damage. I replaced the oil, filled the ram and topped up the tank to the right level. Sadly I am still getting no pressure to split anything and the problem seems to get worse as the oil heats up. When first started the pressure gauge reads 0 then jumps to 500psi once the ram makes contact with the wood, and there it stays. The engine doesn't bog down and the ram just stops. As the oil heats up this pressure drops to around 300psi. If I hold the control valve in the half open position the pressure jumps to 3000si, which is pumps working pressure, so I am confident eh pump is working fine. No obvious oil leaks either. I am stumped as to what may be causing this problem and am at the limit of my hydraulic knowledge. Any help greatly appreciated. Splitter specifications are:

Engine: 11hp Diesel, 3600rpm working speed
Pump: CBNA 16GPM 2 stage pump, working pressure 3045psi @36000rpm
Ram: Unknown brand, 37ton
Valve: Unknown brand, 5300psi max, 25GPM max, 3000psi relief

 

[ChoppyChoppy]

What pressure do you see with the cylinder run all the way in or out?

 

[Troy Field]

If I run the cylinder either in or out then hold the valve in that position the pressure still doesn't climb above the 500-600psi mark.

 

[Haywire Haywood]

Seals blown on the cylinder so the oil just flows past the piston or the pump is shot. Cap the line going to the cylinder from the valve and see if it will build pressure that way.