Kubota KX121-3

[windyvalleyfarmtabby]

Excavator starts but will not move. It obviously has down pressure. But it will not move period. The boom will not move the thumb will not move absolutely nothing. New machine to us so we are a little confused. I checked all the fuses below the seat and all are good. Can someone please help?

 

[Seven Gables]

Are you dropping the safety lever down on the left side of seat? If you are could very well be the safety switch under the lever. Try wiggling the wires or tapping on the switch while activating a function like boom up , sometimes this will momentarily let it come to life

 

[jdtractor]

Already been stated… make sure the lock out lever to the left of the seat is down or all the way forward. It usually has a red handle… good luck. This would be my suggestion.

 

[windyvalleyfarmtabby]

Are you dropping the safety lever down on the left side of seat? If you are could very well be the safety switch under the lever. Try wiggling the wires or tapping on the switch while activating a function like boom up , sometimes this will momentarily let it come to life

Yes its down all the way.i know how to run the machine just all this electrical stuff is not my gig.

 

[Seven Gables]

Another question to help diagnose the issue. Does that machine use mechanical linkage to operate the dozer blade and also the cab swing? Do these functions work? If they are mechanical linkages and don’t work it would indicate a hydraulic related issue, possibly a stuck open master control valve or pump issue.

 

[hayden]

Another question to help diagnose the issue. Does that machine use mechanical linkage to operate the dozer blade and also the cab swing? Do these functions work? If they are mechanical linkages and don’t work it would indicate a hydraulic related issue, possibly a stuck open master control valve or pump issue.

Excellent suggestion. The dozer blade is definitely mechanical. Also perhaps the boom swing. I'm sure there are test ports when you can check for pressure to help narrow things down too.

 

[Mike1955]

Yes it’s down all the way.i know how to run the machine just all this electrical stuff is not my gig.

He is correct. That’s how it act when this lever is not activated. On mine, when I engage this thing it makes a little hydraulic sound. Hope this helps

 

[4570Man]

Another question to help diagnose the issue. Does that machine use mechanical linkage to operate the dozer blade and also the cab swing? Do these functions work? If they are mechanical linkages and don’t work it would indicate a hydraulic related issue, possibly a stuck open master control valve or pump issue.

A 121 excavator doesn’t have any electrical controls beyond maybe the thumb. The main controls are hydraulic pilot controls. Hydraulic pilots are pretty reliable. They might leak a little bit but complete failure of all of them is extremely unlikely. The lap switch lockout controls a solenoid actuated valve that blocks off all the hydraulic flow when it’s up. I suspect that valve or the 12 v source that feeds it isn’t working correctly. Thats where I would start troubleshooting. I don’t think my KX-040 will move the blade or the boom swing with the lap switch up so that test doesn’t prove anything.

 

[Seven Gables]

A 121 excavator doesn’t have any electrical controls beyond maybe the thumb. The main controls are hydraulic pilot controls. Hydraulic pilots are pretty reliable. They might leak a little bit but complete failure of all of them is extremely unlikely. The lap switch lockout controls a solenoid actuated valve that blocks off all the hydraulic flow when it’s up. I suspect that valve or the 12 v source that feeds it isn’t working correctly. Thats where I would start troubleshooting. I don’t think my KX-040 will move the blade or the boom swing with the lap switch up so that test doesn’t prove anything.

Yes I understand completely how the pilot lock out system works, the lockout switch must get power to the pilot lockout solenoid valve which then opens and allows pilot oil to the joysticks and all other Pilot operated functions. However I believe on the older 121 they used mechanical linkage to the blade and house swing directly to the directional control valves in the main valve stack. Now on your 040 and correct me if I’m wrong they changed this to all pilot operated controls off all Valves in the main valve stack. You’re 040 will not operate any functions with the lockout lever raised . With the 121 there is nothing to lock them out, nothing electrical or pilot oil involved, just mechanically operated.
I would agree his most likely cause is either the pilot lockout switch or the pilot lockout solenoid valve. One of his first tests should be to check for power at the solenoid valve when the lockout lever is down . If no power then it’s most likely the lockout switch or the lockout relay. Did you know there’s a relay involved? Now if he does have power to the lockout solenoid then it is most likely the lockout solenoid, either the coil is faulty or the tiny spool valve is stuck.
The lockout solenoid can also very easily be checked by removing the cap on the electromagnet end and insetting a small Allen wrench to manually shift the tiny spool valve and thus allow pilot oil flow to the joysticks and all other Pilot operated controls.

 

[hayden]

The thing on a 121 is that although most of the controls are pilot valves, a few are not and are mechanically locked in position when the safety lever is up. This is definitely true for the track controls, but I can't remember for others.

So if the safety lever is down and the pilot controlled functions don't work, but the non-pilot valve functions do work, then there is an issue in the pilot control system, not the main hydraulics.