SPIDER & BEARING AS 1720871 - Caterpillar

The probable root causes are listed below:
Faulty Crank Enable Switch
Start Enable Relay circuitry from the Electronic Control Module (ECM)
"Deck Start/Run/Kill" switch
Battery cables and/or batteries
Starting motor
Hydraulic cylinder lock
Engine accessory
Internal engine problemPerform the following checks:
Ensure that the shutdown switch is in the OFF position. Use the Caterpillar Electronic Technician (ET) to confirm the switch status. Check for CID-FMI 337-02. If the CID-FMI 337-02 is active, perform the diagnostic functional test Troubleshooting, "Emergency Kill Switch".
Ensure that the Crank Enable Switch is not faulty. Measure the voltage across the 9X-8124 Magnetic Switch between pin 3 and pin 4. The voltage should be 24 5 VDC. If the voltage is not within this range, something is wrong with the circuit. Check the wiring.
Check that the "Deck Start/Run/Kill" switch is not in the KILL position.
The following items should be checked for loose connections and corrosion: battery posts, battery and battery cables Clean the cables and/or connections if corrosion is found. Load test the battery. Refer to Special Instruction, SEHS9249, "Use Of 4C4911 Battery Load Tester" for more information. If necessary, charge the batteries. Refer to Special Instruction, SEHS7633, "Battery Test Procedure".
Test the operation of the starting motor. Check the system wiring to the starting motor. If equipped, inspect the Caterpillar Prelubrication System for proper operation. Refer to the diagnostic functional test Troubleshooting, "Starting Motor System".
Remove the fuel injectors and check for fluid in the cylinders.
Inspect the engine accessories if the engine will not turn. Remove the engine accessories and inspect the engine accessories that can lock up the engine. Repair the engine accessories and/or replace the engine accessories. Refer to Systems Operation for additional information.
Ensure that the timing pin is not left in the flywheel housing after you set the valve lash. Use the 9S-9082 Engine Turning Tool and attempt to manually turn the engine. Disassemble the engine. Inspect the engine for internal component damage. Refer to Disassembly and Assembly Manual.