Fault Phenomenon: Dingli GTBZ20 telescopic boom aerial work platform when starting, the starter motor spins at high speed but the engine does not turn.

Troubleshooting Process:
– Checked one-way clutch: clutch slipping.
– Checked flywheel ring gear: ring gear missing teeth.
– Checked motor shaft: spline worn.
– Checked electromagnetic force: insufficient solenoid travel.

Root Cause: The starter motor one-way clutch is worn and slipping.

Required Parts: Starter motor one-way clutch or motor assembly.