Fault Phenomenon: Caterpillar 320 excavator all actions are slow and weak, engine RPM normal.

Troubleshooting Process:
– Checked main pump: swashplate angle cannot increase.
– Checked control oil: pilot pressure too low.
– Checked compensator: power regulator stuck.
– Checked filter: suction filter clogged.

Root Cause: The power regulator (LS valve) of the main hydraulic pump is stuck in the small displacement position, unable to increase flow with load.

Required Parts: Clean or replace main pump regulator assembly.