- There may be air in the load sensing signal circuit.
- The pump flow compensator spool may not be adjusted properly.
- The load sensing relief valve may not be functioning properly.
- The pressure compensator spool may not move.
- The signal duplication valve may not be functioning properly.
- There may be a internal leak or internal blockage in the load sensing signal circuit.
- The control lever is not calibrated properly.
- There is an electrical problem.
Be sure that your machine pauses before the machine supplies pressure to all circuits. If this is the case then you should proceed with the following procedures.
There May Be Air In The Load Sensing Signal Circuit
There may be air in the load sensing signal circuit. Purge the air from the hydraulic system by cycling the system several times.
The Pump Flow Compensator Spool May Not Be Adjusted Properly
Make sure that the flow compensator spool in the compensator valve is adjusted correctly. Perform the margin pressure test. Refer to Testing and Adjusting, "Hydraulic Pump - Test and Adjust" for your machine.
The Load Sensing Relief Valve May Not Be Functioning Properly
Verify that the load sensing relief valve opens at the correct oil pressure. Perform the high pressure stall test for the hydraulic pump. Refer to Testing and Adjusting, "Hydraulic Pump - Test and Adjust" for your machine.
The Pressure Compensator Spool May Not Move
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| Illustration 1 | g00850889 |
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(1) Flow compensator spool
(2) Orifice | |
Make sure that flow compensator spool (1) moves freely. Repair the compensator valve, if necessary.
The Signal Duplication Valve May Not Be Functioning Properly
Make sure that the signal duplication valve is operating properly. If necessary, replace the valve.
There May Be A Internal Leak Or Internal Blockage In The Load Sensing Signal Circuit
Make sure that the signal that is flowing to the compensator valve is not blocked. Perform the margin pressure test. Refer to Testing and Adjusting, "Hydraulic Pump - Test and Adjust" for your machine.
If necessary, adjust the flow compensator spool in order to set the correct margin pressure. If the correct margin pressure cannot be achieved, there may be blockage in the load sensing signal circuit. Refer to Testing and Adjusting, "Hydraulic Pump - Test and Adjust" for your machine. Repair the circuit, if necessary.
The Control Lever Is Not Calibrated Properly
Be sure that the control lever position sensor is calibrated properly. Refer to Testing and Adjusting, "Hystat Operator Control Calibrations" for your machine.
There Is An Electrical Problem
Check all electrical connectors in order to make sure that the connectors are not loose or have a bad connection. Inspect all electrical wires in order to make sure that the wires are not damaged in any way.