Fault Phenomenon: Caterpillar 320 excavator all actions are sluggish, control levers feel heavy, unable to move spools.

Troubleshooting Process:
– Checked pilot pump: pilot gear pump worn, internal leakage.
– Checked pressure reducing valve: pilot pressure reducing valve set too low.
– Checked filter: pilot oil filter clogged.
– Checked lines: line leakage.

Root Cause: The pilot gear pump is internally worn, reducing volumetric efficiency and unable to build sufficient pilot pressure (typically 39-41 bar).

Required Parts: Replace pilot gear pump.