C15 – Engine Will Not Crank

Probable Causes

Note: This is NOT an electronic system problem.
Refer to Testing and Adjusting for additional information.
The probable root causes are listed in order below:
• Batteries
• Starting circuit
• Starting motor solenoid
• Starting motor
• Flywheel Ring Gear
• Transmission
• Engine accessory
• Hydraulic cylinder lock
• Internal engine problem

Recommended Actions
Perform the following diagnostic procedures in order:
1. Inspect the batteries.
a. Charge the batteries. Refer to Special Instruction, SEHS7633, “Battery Test Procedure”.
b. Load test the batteries. Refer to Special Instruction, SEHS9249, “Use of 4C-4911
Battery Load Tester for 6, 8 and 12 Volt Lead Acid Batteries”.

2. Check the vehicle wiring to the starting motor solenoid. Refer to the OEM vehicle manual.

3. Check the engine start switch and the relay for switch power.

4. Inspect the starting motor cables for damage or loose connections.

5. If the starting motor cables are corroded, remove the starting motor cables and clean the starting
motor cables.

6. Test starting motor operation.

7. Inspect flywheel ring gear for damage.

8. Ensure free movement of the driveline.

9. Remove engine accessories that may lock up the engine and inspect engine accessories that may lock up the engine.

The following list illustrates examples of engine accessories that may lock up the engine:
• Air compressor
• Power steering pump
• Engine oil pump

10. Check for fluid in the cylinders (hydraulic cylinder lock) by removing the individual
electronic unit injectors.

Note: Drain the fuel from the cylinder head. Fuel will flow from the cylinder head into the cylinders when the electronic unit injector is removed.

11. Disassemble the engine. Inspect the internal components for the following conditions:
• Seizure
• Broken components
• Bent components

Refer to Disassembly and Assembly.


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