hydraulic problem on Cat 330b excavator

It is possible that these functions are fed from one pump. Trace the pressure line from each pump back to the control valve to see if all from one pump. Must check pressure at load sense port. Cat uses sensitive load sensing system. Could be a number of things causing slow reaction or low hydraulic power. I have dealt with problems similar to this in the past. Must check pump output pressure before going any further. Are all other hyd functions normal ie. left hand track movement.

Hi Chutzy
Thanks for the reply. Yes all the other functions are completely normal. Perhaps you could give me a brief list of what the problems could be. Unfortunately the machine is about 100 miles away so I can't readily refer to it.

First I would check pump output pressure at load sense port on pump in question. Determine if the hyd functions are slow or weak or both. Swing pressure for 330B would be anywhere from 3200-3900 psi. Travel from 4000-5000 psi. A simple easy test you can do to narrow your search is to swap circuit relief valves to see if problem follows relief valve. If load sense reads low possible problem with P.C.O relief valve. If pump strokes, builds high pressure, but is slow doing so possible margin pressure adjustment required. L.S signal acts on pump output pressure plus margins pressure if margin pressure is not right may not allow pump to reach full stroke therefore not displacing the required oil in a given time frame. Saying all this is fine, I try to check all the simple things first!!!!. The reason the pump was replaced was??? Could there be debris in control valve?

Hi,

I am having the exact same problem as Jimech. Please help me out.!

Hi Jimech,

Please give me some direction if you have found the solution to this problem. Many thanks.