Fault Phenomenon: XCMG XR280 rotary drilling rig engine power low, stalls under high load, manual primer pump feels no resistance.

Troubleshooting Process:
– Checked transfer pump: disassembly revealed diaphragm ruptured.
– Checked fuel: fuel mixed with air.
– Checked push rod: drive push rod worn.
– Checked filter: primary filter clogged.

Root Cause: The rubber diaphragm in the mechanical fuel transfer pump ruptured due to aging or fuel corrosion, unable to build sufficient transfer pressure.

Required Parts: Replace fuel transfer pump repair kit (includes diaphragm).