John C.
Senior Member
OK ,so I understand this correctly, You put a flow meter in the system and then cranked the valve on the flow meter in to get 2800PSI on the gauge and ran things that way until system was warm. Is that correct?
So everyone else knows a little more about the system I'll put some more information here. The system is CLSS which mean closed center load sensing system. Basically the pump output is set to be about 300 PSI higher than the oil leaving the control valve going to a function. Once the pump pressure and the load sensing (LS) pressure are the same the pump is at minimum stroke. There is no such thing as "Standby Pressure" in the Komatsu systems. In essence in normal operating mode the main relief very rarely ever opens. The only time it will open is when the power up function is operated. There is a button on the left control handle that when pushed will max out the flow of the pump and raise main relief pressure to a higher point. When you put the machine in travel you also get the higher flow and raised main relief pressure. The other way to apply this is to set the swing brake and operate the swing in either direction. Komatsu actually recommends setting the swing brake and operating the swing for several minutes in the morning before putting the machine to work, just to warm up the oil.
Back to the current issue. You only have one pump running the whole machine in this size range. I don't know where you are testing LS pressure from but that reading you are stating is wrong. If there was that much difference between LS pressure and pump discharge pressure the engine would be dragged to a complete stop. What your problem sounds to me like is that the TVC pressure has drifted down some. It is not a pressure that you can plug a gauge into and read. If you look at the photo you posted and see the fitting I spoke of with the paint knocked off it. Behind that fitting is a bulbous looking connection, basically a banjo type bolt. That is where you adjust TVC at on this particular pump. Loosen the nut holding the bulb tight just enough that you can turn the fitting and hose attached to it. Underneath that is a lock nut holding what is actually a bolt adjuster that is the center part going through the bulb. Mark where the bolt is at currently so you can go back if it doesn't work when you adjust it. Going in will increase pump output. I usually worked them in half flat increments because it doesn't take much to start dragging down the engine. You don't want to draw the engine down much more than 150 RPM under full load. I usually adjusted the bolt with the engine shut down and then tested operation. I have done them when running but sometimes it will blow one of the O rings in the banjo fitting.
Good Luck and let us know what you find.
So everyone else knows a little more about the system I'll put some more information here. The system is CLSS which mean closed center load sensing system. Basically the pump output is set to be about 300 PSI higher than the oil leaving the control valve going to a function. Once the pump pressure and the load sensing (LS) pressure are the same the pump is at minimum stroke. There is no such thing as "Standby Pressure" in the Komatsu systems. In essence in normal operating mode the main relief very rarely ever opens. The only time it will open is when the power up function is operated. There is a button on the left control handle that when pushed will max out the flow of the pump and raise main relief pressure to a higher point. When you put the machine in travel you also get the higher flow and raised main relief pressure. The other way to apply this is to set the swing brake and operate the swing in either direction. Komatsu actually recommends setting the swing brake and operating the swing for several minutes in the morning before putting the machine to work, just to warm up the oil.
Back to the current issue. You only have one pump running the whole machine in this size range. I don't know where you are testing LS pressure from but that reading you are stating is wrong. If there was that much difference between LS pressure and pump discharge pressure the engine would be dragged to a complete stop. What your problem sounds to me like is that the TVC pressure has drifted down some. It is not a pressure that you can plug a gauge into and read. If you look at the photo you posted and see the fitting I spoke of with the paint knocked off it. Behind that fitting is a bulbous looking connection, basically a banjo type bolt. That is where you adjust TVC at on this particular pump. Loosen the nut holding the bulb tight just enough that you can turn the fitting and hose attached to it. Underneath that is a lock nut holding what is actually a bolt adjuster that is the center part going through the bulb. Mark where the bolt is at currently so you can go back if it doesn't work when you adjust it. Going in will increase pump output. I usually worked them in half flat increments because it doesn't take much to start dragging down the engine. You don't want to draw the engine down much more than 150 RPM under full load. I usually adjusted the bolt with the engine shut down and then tested operation. I have done them when running but sometimes it will blow one of the O rings in the banjo fitting.
Good Luck and let us know what you find.
