Construction and Road Equipment
Have a komatsu sk1020 skid steer. have a problem with the work equipment as it is not working when engine is started the
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Customer: hi have a komatsu sk1020 skid steer. have a problem with the work equipment as it is not working when engine is started the hydraulic pump goes under load and pressure at valve block is 200 bar at neutral. checked gear pump and is fine checked pilot pressure and is fine ,disconnected servo pipes at block and pipes going to hyd cylinders and no flow which is fine. the only thing I did notice is was oil coming out off a servo port on the valve block on the bucket slice.took apart valve block and went threw every valve and washed it out saw no damage. put it back together and still have the same problem, no movement and high unload pressure .did anyone come across this problem, I know problem is in valve block but don't know where
Answered by curtis b in 15 hours 9 years ago
curtis b
Auto Mechanic
75,234 satisfied customers
Specialities include: Auto Body Technician, Heavy Equipment Repairs, Heavy Duty Engine Repairs, Brake and Transmission Repairs
Hi my name isXXXXX will try to help. If the pumps are good and making good pressure than you could likely have a safety interlock circuit problem disabling your functions. Check your safety interlock circuit and switches to be sure all switches are functioning and the harness checks out OK. Let me know the results and ill help any I can.
Customer
do you mean my servo pressure from levers ,if so they are fine and is sending down pressure problem is I have too much pressure in neutral
Thanks for the info Ger.What is the serial number?
Customer
Sk1020-5
S no 37c f00159
Hi Ger. I will be out on a job today so let me opt out in case someone can help you sooner as I will not be able to dig into this further until tonight when I get back. If no one has picked this up I will follow up with you and continue on.
If the pump pressures up on start up, what is happening at the return line? Could the return be plugged or the line pinched? The flow should be straight through the valve and back to the tank through the return, I would be checking the return side of the valve block.
Customer
Checked that and it is fine.looped the pressure pipe from the pump to the tank pipe and it flowed perfect
So the blockage is in the valve block. What valve is stuck in wrong position?
Customer
Thats my question took valve block out and stripped every valve and all looked fine and smooth cleaned every port and steam washed it out . Can not fimd anything
Are all pilot lines off valve? No pressure from any?Have you air checked valve on bench? Should be matter of finding which valve spool is not centered.??
Customer
Did all Of what you said and spools returned to centre opened up oulet pipes and no flow while pressure was high
Valve has to be moving to a closed position! You say it is open before engine is started? With no pilot pressure to any spool,the valve should be free flow back to tank. Not happening! I will opt back out and maybe Dan will have better idea when he returns . Please do not respond to me, or it locks the question. Sorry.
Hi, Check your return circuit for restrictions. Click here for your return circuit diagram. Check your filter for metal/debris that would indicate a potential pump failure occuring and check your oil cooler for restrictions click here. If Ok and your pumps are under a load instantly on start up you could have a control problem to your pumps causing the pump to stay stroked when they shouldnt be. Click here for the pump servo/ pump control diagram. Also, check your pump signal pressure which should be equal to pilot pressure. Reply back with your results and if you need further help with this and Ill be glad to help.
Customer
Hi dan
Thanks for replying. Checked the return pipes and all is fine .servo pressure is fine and work equipment pump is fine .work equipment pump is a gear pump so is not variable and dose not depend on a signal from valve block
Good Morning and thanks for the update. This is a load sensing hydraulic system. According to your serial number this is your main pump. There is a standard and a high flow pump for this machine. Let me know id this looks like the main pump on your machine. The other picture shows the pilot pump mounted to the end of the main pump.
Ger, Click here for a downloadable troubleshooting guide for your serial number with schematics and troubleshooting specs for under 15 dollars. there are other manuals available for your machine on this site as well. Unfortunately I do not have the manual for your serial number machine to be able to post these specs but this downloadable copy should provide you with the test specs and schematics you will need. Cut open your return filter and check it for metal. Let me know the results and if I can help you further.
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