Have a 320d that has low lh track power and stick power. Swivel joint has been resealed, track motor inspected, system flow tested, main relief pressure cracks off at 6000 psi. On low idle rh pump will relief at 6000 psi and lh only reaches 3200 psi and stalls the engine down. Thanks guys for reading and any ideas or fixes would be appreciated
You need to sperate pressure from flow in your problem and your one pump that shows 3,200 psi is your problemarea. Look at the hydraulic schematic and I sure it will show one pump feeds each side of the control valve so that each track is supplied oil from each pump, P1 and P2. If P1 runs left track it will also be usede as half of the total flow for the arm circuit as arm in and boom up use a spool in each side of the control valve to combine flow of both pumps. You mentioned the items that were flow tested, what are the circuit cycle times ? Your service manual should give you a spec for allfunctions. Remember flow is speed ,pressure is power. Gotta finish breakfast and get going, I`m sure others will add more than I have, good luck.
You have a problem with the control of one side of the main pump. Likely the NFC valve. If you could find the NFC lines and remove them from the pump and plug them for at test would help. The NFC signal comes from oil flow through the open center of main valve. Flow gives NFC pressure and that tells the pump you are doing nothing so the respective pump halves stay at minimum angle and flow. When a control is used the flow and NFC pressure drop and the pump half feeding that half of the valve opens up to feed the circuit. I suspect that isn't happening on one half of your pump. This can happen if the NFC relief valve is plugged, oil is slow to bleed off and pressure drop. Or the control on the pump could be worn. If you remove the lines the pumps will open up to max flow on start. Don't run long this way. Also when running with lines off very little oil should come out of the pump NFC control. Need some one to post deg of pump and lines to show you the right ones. Later Bob
So left pump only reaches 3200psi AND stalls the engine at the same time, is this correct? What pressure do you see for right pump while doing this?
Sounds to me the left pump is staying fully stroked. It could be a NFC issue but the oil will be being bled off to command that. Likely from the lh travel spool, which if I remember right, is located inside the stick spool, which should be the last valve. That could also explain why both functions are showing poor performance.
Are you sure one pump runs each side or do they both work together with a compensation valve in order to travel in a straight line ?
Im not sure of anything, But Hitachi calls it a flow combiner valve. One pump runs one track and the other pump runs the other side. If while traveling you use a front function, without the valve you would starve the one side and the machine would go in circles. The flow combiner valve shifts and diverts one pump to run both tracks, slower, but still goes straight. Release the front function and the flow combiner valve goes back to normal and the pump flows back to it`s normal operation.
The 320 does the same, likely most excavators do. Later Bob
So if one pump was weak wouldn't it slow the other track down to match track speed ? ........ Unless the combiner valve was bad ?
There is a logic control that keeps one pump feeding one side untill you are driving both tracks and pull in one more circuit. At that time one pump feeds both tracks and the other feeds the used circuit, there is also an orifice that allows any unused flow to join the travel oil. You can check the operation by traveling and working a circuit, travel is straight but slow, as circuit ends travel but still held in machine speeds up, let go of circuit and machinemspeedsmup more. Later Bob