We have problem with CAT 5090B, engine loading when we unlock the hydraulic lock lever, the load was remove when we unlock the hydraulic lever even we try to block the load sensing line, ps to the main pump but nothing change. Please share with me your experience to help solve this problem . M THANG
Does the machine have auxilliary hydraulics?
Hmm, just looked up a 5090B. That's a big machine! Front shovel? I Doubt it has aux hydraulics. I don't recall seeing someone discuss a problem of a Cat that size here, not saying they haven't though. I don't know how similar the 5090 is to smaller excavator machines, but on them when you unlock the safety lever to operator the machine, all it does is allow pilot oil pressure to the machine controls. Of course on a machine that big, that pilot pressure can go to any number of controls and solenoid valves that control the output of the pumps. I don't have any ideas of what's causing your problem, but it sounds like something is telling the pump to stroke out as soon as you active pilot pressure system.