Fault Phenomenon: Caterpillar 336 excavator hydraulic pump displacement locked at maximum or minimum, unable to self-regulate.

Troubleshooting Process:
– Checked feedback rod: feedback rod connecting to swashplate broken or detached.
– Checked pivot point: ball joint worn and detached.
– Checked regulator: internal regulator stuck.
– Checked spring: spring broken.

Root Cause: The mechanical feedback rod of the hydraulic pump variable mechanism broke, preventing the pump from receiving LS pressure signals for displacement adjustment.

Required Parts: Replace feedback rod and ball joint.