Long time forum reader for knowledge and advice, newbie member. I have a Kubota Kx121-3 that has no hydraulic movement. The pilot pump is supplying pressure to valve block and I also have change valve pressure with safety lever down. Looking at the schematic I then checked pressure at bottom of valve bank of Pps and Pls and do not have any pressure at all. I can try to figure out how to post a schematic if anyone would like to have a look. I'm hoping for some advice before I take the machine somewhere to be diagnosed. If I don't have any pressure I assume either pump or unload valve or maybe a control valve is just dumping flow to tank. FYI my uncle was last owner of this machine and this has happened a few times before I bought it but the problem has always just went away. It's been sitting for a while at my father in laws, went to float it home, started right up, got on trailer fine then when I got home to remove from trailer nothing would work... thanks for any input...
P.S...I also have already removed unload valve spool as well as main control valve relief, inspected and cleaned, although I may have missed something..
Good day According to my schematic we have a solenoid valve between the pump and distribution, have you a gauge to check if this is as it should be ? Kind regards Uffex
Oops should I mention if you have a pattern change valve check it is in position.
Uffex, thanks for your reply. The pattern change is in position. I checked with gauge and have PSI after the solenoid yes. I should mention even the dozer blade does not move as I believe this is not controlled by the solenoid.
Good day Travis I not to sure where you have checked the pressure after the solenoid valve the feed line connects to the slew brake then returning to connect to the remote controls. Take a look at the attachment to be sure we are on the same page. Kind regards Uffex
Hello, I had my gauge right into the outlet of the change valve. Where it leaves the solenoid and goes to the slew brake and the travel lock cylinder. Should I try to follow that line and test at more places?
Do you mean you have zero pressure at that point ? You should see about 40 bars 500 psi
If we simplify the schematic, maybe help. See attached
Sorry, outlet of the change valve does have about 500 psi.
Ok we can discount the solenoid and pump but if I understand you correctly there is zero at the remote controls?
The problem is nothing will move, dozer blade, tracks, boom etc. Some of these actions are controlled mechanically with a linkage.
Good day Travis Your post has all the symptoms of a control lock out failure be it the solenoid valve, can you please hook a gauge into the line that runs to the swing brake and test for pressure. Kind regards Uffex
Hey, the line that goes to swing brake comes from the "change valve" correct?
Hi Travis Yes that is according to my schematic, may I suggest follow the output line from the small gear pump, it should go through a filter attach to an accumulator then to the solenoid valve. Mark the line at the solenoid, take a photo and post it. The slew brake has a number of lines, you can follow those back and note which goes into the solenoid valve. Kind regards Uffex
Hi Travis I am sorry for the differences in industry terminology, manufacturers use university grads to write manuals all have a new interpretation of a common part "change valve" is also called "Lock" in the same document both of which mean "Control lock out" self-explanatory blocks the use of levers & pedals. Sorry if this is confusing, a bug bear of the machines we work with. One day the industry will adopt common expressions helping all concerned.
Uffex, I understand what you are explaining. That solenoid has a tee, one line to the "travel lock cylinder" and one to the slew brake (which tees of again). I have 400-500 PSI at the valve where it tees to slew brake and to travel lock cylinder. Thanks, Travis
Good day Travis Can you check to see if we have pilot pressure from the R.C.V. at the main valve stack, take one that is easy to get to, no matter if it boom bucket or arm. Kind regards Uffex
I will check this later on today and report back. Thank you for you're time.
Looking at say the dozer blade valve, it is controlled by mechanical shuttle, not hydraulic pilot shuttle, if I have a pilot control issue shouldn't the dozer blade still work?
hi Travis indeed the dozer should work irrespective if you have servo pressure or not.
Right, the dozer does not move, nothing will move.
Ok that could be main relief lodged open or main pump defect, any strange noise from the pump - any witness stuff in the filters? Kind regards Uffex
Small pilot filter was really dirty, I just found out it was there and judging how bad it was previous owners didn't change it either. I do not hear any strange noises. I'm not sure how to test the pump. I removed control valve main relief and everything seemed OK but I'm not positive.
Good day Travis One possible cause came to mind however when this happened for me all functions worked but very slowly, you have a small 0.7mm orifice in the load sensing line if this was obstructed it would prevent the pump from coming off minimum flow. You can see this in the schematic at the very end of the MCV. Kind regards Uffex
Good day, I had that orfice out, cleaned it and no difference. I installed a gauge on the bottom of the MCV to see pressure on that load sensing and the gauge didn't show any signs of pressure.
Good day The pressure would only show up when you used a function if that was the case it points more to the main pump - drive failure or pump defect. Kind regards Uffex
That's where I'm beginning to believe my problem is also. With no operator function being used would my main pump probably have some pressure? Should it have "standby pressure" of approx 400 psi , the setting of relief valve " a3 " on the schematic?
Good day Travis Before we condemn the pump just make sure the high pressure valve in the inlet section is not lodged open. Kind regards Uffex
I'll check that again tomorrow, had it out before and it appeared to be OK but I'll have another look. What about the main relief on the outlet valve? Could that one be an issue?
good day Travis Main relief (A3) is a possibilty you should have stand by pressure at port "P", check out the main relif first and then if you have no stand by pressure we are back to the pump. Kind regards Uffex
I had a3 off the inlet and a1 off the outlet valve. Can not see anything wrong with either. I removed P line from inlet valve and blew air into the valve. With the return lines removed I get some air coming out of the outlet valve at the tank line. I assume the air would have to be bypassing the relief a1 to be coming out on the tank line. I'm not sure if this is a sure sign of a1 relief trouble..?
Oh, disregard my last post. I read of my manual more and I believe that a1 main relief on the outlet should in fact have slight bypass on low pressure passage, it does not go right to tank, it goes to the oil cooler.
I know this is an older post but Just curious what the diagnosis ended up being? I have the same machine with the same exact symptoms ive been fighting intermittently for some time.
I realize this is an old post but thought I could jump in as I am just curious if hyd. pump failures are common on the 121-3 machines. I am aware of two local owners that have had what I would consider premature failures at between 22 and 25 hundred hours. The machines were from the 2007 era.
Cześć, czy udało Ci się rozwiązać problem? Mam identyczny, ale w Kubocie 161.