Hey guys I am having a little problem with a old komatsu pc210lc-3 . Pump was rebuilt a while back . machine sat for probably a year or two . never had the NC , CO or TVC valves properly adjusted . I tried doing it according to the shop manual . TVC valve pressure doesn't change from 200psi but it does adjust the load on the engine . only when I relieve a function the tvc pressure goes up . (actually went up to about 1200 psi at one point) . NC valves are the only things that seem to work . I adjusted them to the specified values about 100 psi all levers at neutral CO valves seem to not work properly . but they do read about 60psi when I relieve the pump . but when I try to adjust the readings do not change . was also confused because the shop manual does not specify what is the CO valves standard pressure . I see two possible answers which can either be 5 kg/cm2 which they labelled as (lowered hydraulic pressure) . or minimum 18 kg/cm2 which is the NC valves pressure when lever is at full stroke .. was a bit lost because i know the NC valve is only actuated when all levers are at neutral . I actually got the machine to work ok but then I just needed to adjust the CO valve for the front pump and when I tried doing that everything that works on that pump got really slow and lacked power .. I tried adjusting it to its original position and no results, I took the screw right back out till it was not making contact inside same thing . sent the screw in a bit no change , sent it right in same thing .. from that point I stopped and decided to do some more research because it seems as though that valve is not responding as it should . tomorrow I am going to check over everything again . starting with differential pressure of the jet sensor .. any assistance would be greatly appreciated !
Do you know where all the test ports are and which adjusting screw adjusts which pressure? If so I can walk you though the procedure. The book is written like it was translated from Japanese and is very hard to understand.
isnt every komatsu manual?
I have a fair understanding of each test port .. nc and co valve are from the same test port under the pump front and rear , tvc valve test port is behind the front pump nc + co valve . jet sensors are on the lines high pressure (engine side) and low pressure .. I know all of the adjustment points also .
I'll run through the procedure I have used for years then. I start by setting pilot pressure. Once done with that the NCs are set by adjusting the jet sensor reliefs on the main control valves to get about 72PSI on the pump servo pressures. Do this with the engine at high idle and the mode switch in H. Now check and set the main relief pressures. When that is done you can adjust the COs so the servo pressure is again at 72 PSI with system over relief. I usually do this on the boom or stick circuit so I don't get the CO cancel involved. Once those are set you can adjust the TVC. You can do it with a gauge installed but I used to just adjust it by how much it pulls done the engine. I didn't want the engine to lose more than 150 RPM. If you use a gauge I set it at 270 PSI with one pump over relief and then check engine RPM with two pumps over relief. Good Luck
this machine only has 2- stage olss so only have S and L options . tried adjusting tvc valve as you stated . but again no change . any suggestions ? I did follow in that order . I notice that you don't mention the differential pressure of the jet sensor . that is measuring hi and low sides and adjusting that way . any specific reason for this ? these are the valves that my machine has .
i believe it is the earlier -3 series . if that changes anything
You provided a big clue when you said you only of the two mode system. It means you don't have a computer in the machine, only a resister that provides two settings on the TVC. In your case just adjust the TVC screw to set your engine RPM drawdown to your preference in the S mode. You likely don't want engine RPM to drop more than a hundred RPM in this configuration but the book might give you a spec. On the question of the jet sensor settings, you are indirectly reading the jet sensor differential with the servo pressure. The differential is just an arbitrary reading that may or may not put the NC pressures in the right place. Reading the servo pressure tells you the differential is in the right place. Does the machine walk straight now that you have done all the settings?
yes it walks straight . I have had a few big improvements . all functions were really slow . now it has reached to approximately 85% of performance I would think . it just dies down a lot no matter what I do with the TVC valve . and the bucket close function is a little on the slow side but is powerful . when I relieve the bucket close circuit I do get full pressure 4550psi. I would try adjusting the tvc valve again and see if I get any change .
You can test your performance by running a cycle time on the boom circuit. Stretch the stick all the way out and open the bucket. Set it down on the ground and set engine speed at max and the dial in S mode. Lift the boom as fast as it will go till it tops out. That should take between 4 to 4.5 seconds total. If you get that then your machine is on the spec. If the engine is pulling down a little hard then adjusting the TVC pressure can affect that. I don't recall which way to turn the screw but logically turning it out will put less load on the engine.
ok I will try that . if it doesn't walk straight what would that mean ?
It would mean the pump flows wasn't balanced. One could put out more that the other making one track faster than the other.
so this would be an easy fix if I had this problem ? just asking for future reference
Probably not easy because you first have to make sure other issues were not causing the problem. Bad travel motor or swivel joint are other possible causes so those I usually check out first.