Fault Phenomenon: CAT rotary drilling rig difficult to start on cold winter mornings, starter motor turns but engine does not start.

Troubleshooting Process:
– Checked glow plugs: multiple glow plugs burnt, open circuit.
– Checked relay: glow plug relay not engaging.
– Checked timing: glow time set too short.
– Checked voltage: low battery voltage.

Root Cause: Multiple glow plugs are burnt, causing insufficient combustion chamber temperature for diesel ignition.

Required Parts: Replace all failed glow plugs.