Fault Phenomenon: Foton Raysta L12 PTO functions normally when cold. During high-load pumping (operating temperature), the PTO automatically disengages, accompanied by gear grinding noise, and eventually power transmission is interrupted.

Troubleshooting Process:
– Checked PTO engagement cylinder: cylinder stroke normal.
– Checked air system: air pressure stable.
– Checked PTO gears: gear meshing normal.
– Measured engagement lock mechanism at operating temperature: found insufficient lock pin spring force.

Root Cause: The PTO lock spring anneals due to heat, causing loss of spring force and disengagement.

Required Parts: PTO lock spring and repair kit.