I have a kx121-3 that intermittently has No hydraulic functions whatsoever upon start-up. This has been an ongoing issue for some time now in which i only have limited time to work on/diagnose. I have checked and inspected many relief valves, pump pressures, hydraulic system and all filters have been serviced. All mesh in-line filters ive been able to locate have been cleaned and inspected as well as all orifices (that i can find). So the main pump, when the hydraulics work, has about 500psi standby pressure and will build to 3400-3500psi when you deadhead a function. Same goes for the pilot pressure. When the hydraulics decide not to work Nothing works, no pilot function and No blade or boom swing which are live linkage hydraulic functions that are Not protected by the pilot safety switch. This is the first time the machine has started up with no hydraulics while actually at the shop. With gauges on, while no hydraulic function, the pilot pressure is 500psi but the main pump shows basically no pressure. Im wondering if this is a main pump control valve issue or am i missing a relief valve somewhere that could be sticking? Schematic for this has not been much help. I feel like i may be missing something? Anyone have a similar experience with one of these?
Heres what the gauges show when the hydraulics are not functioning...
Good day Your issue could be down to the pilot lockout, it may be missing the connection from time to time. Not so uncommon. Kind regards Uffex
Uffex, thank you for the reply. If this were the case, would it affect the hydraulic functions not protected by the pilot lockout? Say if one of the selenoids were only opening partially? The boom swing and blade are both linkage operated and are live even with the lock lever up. Neither of those functions work when this happens. Throttled all the way up, the boom, bucket etc. will ever so slightly move but basically only if gravity is on their side. I read an old post from another member that you assisted with this same exact issue with one of these kubotas. However, they never posted back what the fix ended up being. Brandon
I should add that the travel lever lock does indeed unlock when the lever is down in the operate position.
Good day Brandon You are correct, control lock out will only affect pilot control circuits. I overlooked the point that the mechanical functions also lose power. The issue comes back to the pump, any noise when you lose power (Drive coupling). If the signal was not working so good I would still expect movement, be it slow. Any history prior to the problem? Kind regards Uffex
Never had any issues prior to the first time this happend. There are no unusual noises or anything of that sort coming from the pump/drive. When this happens there is 500psi at both test ports on the pilot circuit. At the accumulater block and at the selenoid valve for the control lock. There is enough pilot pressure supplied to actuate and unlock the travel lock cycle as soon as the lever is dropped. I believe it to be something sticking in the pump or something with the control valve for the main pump. Im not exactly sure how the control valve actuates the pump to build pressure without taking it apart though. Seems it Could also be something in the load sensing circuit... Just not sure at this point.
Good day Do you have the pressure checking - adjustment information ? If you can post a photo of the pump label that may be helpful. Kind regards Uffex
I don't have any adjustment info but i believe, from what ive read, 3400psi is max for the main pump and it hits that when you deadhead a function. I will try to get the pump tag info when im back in the shop. May be a couple days though. Brandon
Good day Brandom You are measuring main pressure the machine has Load Sensing. When you operate a circuit the LS pressure comes back to the pump regulation reduced to a certain level activating the pump. The level of the pressure coming back is critical to have the pump work correctly. I do not have that Bcat information it will take some research to find this if you can take a photo of the pump & label then I can help some more. Kind regards Uffex
Uffex, finally got back to the shop and got a pic of the pump tag. Was back to working and loaded up to take to a job and ofcourse it would not move once again when attempting to unload. If i get time today or tomorrow i plan to get some adapters and T into the load sensing line and check the pressure going back to the pump control valve.
Uffex, yesterday i removed the control valve, cleaned, inspected etc. Both orifices on the valve and pump side were cleaned as well but were clear with no debris or blockage so we'll rule out a control valve issue. Back to the picture i previously posted of gauges on the supply and pilot test ports... with it running at idle (when theres no hydraulic function) 500psi on the pilot side and basically nothing on the main supply side... sound more like something internally sticking in the main pump? Its currently not functioning so i cant check but if i remember correctly, back when i had gauges on and the hydraulics were functioning, i want to say there was a constant 500psi on both the supply and pilot side at idle.
Good day The question for me are you getting a lS signal, with a gauge in the Ls line you should see something like 300 psi less than main line pressure when you opertae the arm for example. If the pressure reacts correctly it comes back to the pump. If you can catch the machine working as it should and get the Ls value that would be useful reference when the machine fails. Kind regards Uffex
Previously when i had gauges on and the hydraulics were working, the gauge on the pilot side would signal close to the same pressure as the main pump when a function was used. The gauge is in the accumulator block which is T'd off the line going to the pilot filter which i believe is the load sensing line. On the valve side that ls line comes off the service (top section) of the valve directly next to the pressure switch. Line with the orange mark is ls i believe.
Whatever became of this? Working on a machine now with a similar issue. Thanks
I ended up taking the pump off and over to a hydraulic shop. He took it apart and says the valve plate i believe is a little worn and a couple piston shoes. Having trouble getting the few hundred dollars in parts needed to repair so unfortunately will more than likely end up with a new pump.
Thanks for posting what you have figured out so far. Would like to know end result as they have a model like yours where I work. Simon C
Would like to know if this fixed the problem? Have same issue
I am also experiencing this issue, did you end up with any answers?