Fault Phenomenon: Zoomlion ZLJ5440THB diesel tank functions normally when cold. After high-temperature summer operation (operating temperature), engine power is low, exhaust appears normal, and eventually stalls.

Troubleshooting Process:
– Checked diesel pre-filter: filter not clogged, water drained normally.
– Checked fuel transfer pump pressure: pressure meets standard, no leakage.
– Checked fuel tank breather: breather unobstructed, no blockage.
– Measured pressure inside fuel tank at operating temperature: found negative pressure inside tank.

Root Cause: The fuel tank cap breather valve sticks due to heat, causing negative pressure in the tank and poor fuel supply.

Required Parts: Diesel fuel tank cap assembly.