We have a pc490-10 and occasionally the boom will raise slow. Some other function like stick out and slew seem to also be slow. It is very random. What we are seeing is the rear pump not increase displacement. It sits at 24cc while the front pump will go to 206cc. When the boom functions normally both stroke to 206. Both pumps will deliver the same pressure. Pcc boom up pressure is 380psi when both fast and slow. I have attached screenshots of what the computer is seeing when it is acting slow. Is there a valve that could be randomly hanging that would cause the rear pump to not increase displacement but would still allow it to build pressure? Machine has 7000 hours and has been trouble free up until now. We did a hydraulic service recently and there were no contaminants. Issue had come up prior to the service. The main reason for the service was a leaky return to tank line. Looking for some insight as komatsu doesn’t seem to have any techs readily available.
Well you might want to check your manual. I think your pilot oil is too low. Should be closer to 500psi iirc. If there's no sense of demand, then the rear pump is unlikely to give full flow. Are you working in P mode or E or L?
This is in p mode. I also thought this was on the low side but I am more familiar with Deere where they run around 550. What led me away from pilot pressure issues was it functioning normally with the same amount of pilot pressure. I should have noted it will do this more often with a full bucket but will also do it with an empty bucket.
I will look up specs in AM . That is if Lachou doesn't beat me to it. Did you notice if merge/divide solenoid was energized?
I did not. Does it have a specific callout in the menu or does it need to be checked on the control valve? I’m unsure of the location..
Its in monitoring, pre-selected
I will check in the am. Thanks for your help.
Please see attached
@tbone1471 : You should check 02 items 08000 (Merge-divide Sol Current Main) and 08001 (Merge-divide Sol Current LS) to see what their values are. If their values are correct, then I would say that you should disassemble the Merge-Divider valve to check, most likely this valve is stuck
Sorry to revive a sorta dead post but I have a pc490 that is slow on all functions. The pump isn't stroking and I've checked most of the things in the merge and ls circuits. It's there an way to see if the pump controller is causing this? Is the pump controller a regular failure? I'm a cat field tech and I've been "gifted" this pc490-11 cause it moves too slow to get it far enough away from me.
We never fixed ours. Komatsu came out and has suggested we replace the quick dump valve for the stick circuit on the control valve. Parts showed up but no time to sort it out. They recommended this replacement because they were seeing pilot pressure on both sides of the stick pilot . I.e. when stick in on control we would have a few psi on the pilot for stick extend. Almost like they are fighting each other.
I apologize for not asking sooner, does your machine have a pattern change valve? If those things aren't all the way one side or the other, you get all kinds of issues with boom and stick. This applies to you as well tbone, check for a pattern change and make sure it's all the way in ISO or backhoe. No in between.
We checked ours and the initial issue followed the sticks ruling out the pattern valve. I am supposed to be on that job site tomorrow and if everything works out I am going to put the quick dump valve on.
Not seeing how quick dump is gonna put pilot oil on the other side of the spool. I think I'd be gauging pilot oil at the RCVs. They are monitored, you could observe in the service screen.
After tearing this control valve all to hell and checking all sorts of electrical stuff, if the damned pattern change fixes it I'm gonna have to write one hell of a story. And drink quite a bit.
Well it isn't the pattern valve. I did find that the pmf and pmr pressures are 150psi at low idle and 150psi high idle. Spec is 300/150 tore apart the can behind the main control valve, saw nothing unusual.
What kind of pilot pressure do you have, At the spool caps?
the bucket dig pilot is 175-200psi at the spool and I put a gauge on the #10 epc valve posted on the pic lachau posted above and no pressure ever came to that solenoid no matter what I moved.
Well I knew this was going to end up being weird. I pulled off the pressure reducing valve block and pulled everything out of it. One of the valves has a sharp little pin in it. I took some scotchbrite and cleaned up a wear ring on the pin and stretched the spring out and now it works fine. Everything else in there looked ok other than the pin and seat. I'll order one of those and replace it later, but at the moment its running fine.
Tbone1471 did ya ever fixed the issue? I’m having similar issues. Pc490-10 left track won’t speed up, it travels really slow and looking at the parameters pump 1 is not stroking like pump 2 on the cc/rev it stays under 100 cc/rev and it creeps up but pump w goes to 200 cc/rev instantly.
We have not gotten around to fixing it. Our local dealer is stumped… but I believe it is the merge divert valve spool sticking. Check you hydraulic oil for metal. We had some steel show up which led us away from the electronics.
We ended up putting a merge diverter valve in this machine and it resolved 90% of the issue. I think it was the ls spool in this valve that hung up slightly. It had to be in just the right position to hang up which is why it was not consistent. This was causing a lag or no swash plate movement in pump 2. We now have the pumps stroking properly. But sometimes we have a low power issue or both pumps not stroking enough causing the stick to stop moving out with a loaded bucket or the boom to raise slowly. It seems like it is all the movements not just a single. Both main relief valves were replaced and they are opening around 5250-5500 psi (36MPa). The pilot pressure reads 385 psi (2.7-2.8 MPa). I think this is a little low. But I believe the pressure reducing valve is on the merge diverter and was included with the valve. Any ideas on the next direction to look?
Surprised it was two years to work out the merge divide fault dealer should have put gauges to ls lines on pump and see if pump was getting signal to ramp up, if not follow to control valve, swap lines, fact it was during boom up or single operation shows it's from merge divide which then needed to detirm if it is epc or valve really. They don't always change the self pressure reducing valve I would confirm it 100% as it can cause intermittent faults like you're seeing especially if it was already worn out like you were saying, it's a 700$ aud part not worth stuffing around with. When it does the fault still I'd be watching pilot pressure on dash or gauge in the side of the valve. Then watch ls and see if it drops off as well due to lack of pilot pressure.
The dealer is not very responsive to any issues. They like to sell machines and walk away. I tell them it is get the check and run. I thought the new merge divide came with the self pressure reducer? It is mounted to the side of the merge divert. It has been much better but we still have the issue occasionally. Hydraulic oil is clean no metal. Pump pressure is good. We were going to start looking harder into the pressure compensation valves. I am not certain that is the answer but I would like to resolve it 100%. I have been out to the machine recently and it seems somewhat slow and lacks a little power. In my opinion. We did both main reliefs at the same time as the merge divert and the pressure is good. If I make it to the machine today I will look at the ls and pilot pressure correlation
They don't always come with new spr valve in my experience doing them on 20 tonners it comes seperate, I haven't needed to replace one on a 490 before. I would be checking that for sure if pilot is dropping off everything else will as well. The fact it's on all circuits now makes it the common link. Comp valves would be easy to quickly check, just stall circuits out and see if anything else moves. Not that common on newer machines was more a -6 thing