The possible causes of this failure are listed below:
- The battery is discharged or the battery is faulty.
- The disconnect switch is open or failed.
- The cables to the starter have failed.
- The start relay has failed.
- The ignition switch has failed.
- The engine is locked.
- The starting motor solenoid has failed.
- The starting motor has an internal problem.
The following tables will be referenced in troubleshooting the starting motor.
| TYPICAL SYSTEM VOLTAGE DURING CRANKING AT VARIOUS AMBIENT TEMPERATURES | ||
| Temperature | 24 V System | 12 V System |
-23 to -7° C (-10 to 20° F) |
12 to 16 Volts | 6 to 8 Volts |
-7 to 10° C (20 to 50° F) |
14 to 18 Volts | 7 to 9 Volts |
10 to 27° C (50 to 80° F) |
16 to 20 Volts | 8 to 10 Volts |
| MAXIMUM ACCEPTABLE VOLTAGE DROPS DURING CRANKING | ||
| Circuit | 24 V System | 12 V System |
| Negative battery post to negative starting motor terminal | 1.4 Volts | 0.7 Volts |
| Drop across disconnect switch | 1.0 Volts | 0.5 Volts |
| + battery post to positive solenoid terminal | 1.0 Volts | 0.5 Volts |
| Solenoid terminal "Bat" to solenoid terminal "Mtr" | 0.8 Volts | 0.4 Volts |
Test Step 1. CHECK THE BATTERY VOLTAGE
- Attempt to crank the engine. Measure the battery voltage with the digital multimeter. Measure the voltage at the battery posts. Do not measure the voltage at the terminal of the battery cable.
- Compare the voltage to table 2.
Expected Result:
The battery voltage is equal to or greater than the voltage in table 2.
Results:
- OK - Battery voltage is correct. Go to test step 2.
- NOT OK - Battery voltage is too low.
Repair: Check the charging system. See Special Instruction, REHS 0354, "Charging System Troubleshooting".
Stop.
Test Step 2. TEST THE DISCONNECT SWITCH
- Ensure that the disconnect switch is in the CLOSED position.
- Measure the resistance across the terminals of the disconnect switch.
Expected Result:
The resistance should be less than 5 ohms.
Results:
- OK - The resistance is less than 5 ohms. The disconnect switch is correct. Proceed to test step 3.
- NOT OK - The resistance is greater than 5 ohms. The disconnect switch is not correct.
Repair: Replace the battery disconnect switch.
Stop.
Test Step 3. TEST CABLES FROM THE BATTERY TO THE STARTING MOTOR
- Visually inspect the battery cable terminals for the following conditions:
- Loose connections
- Corroded cables
- Loose connections
Expected Result:
The cables should be clean and the cables should be tight.
Results:
- OK - Battery cables are in good condition. Proceed to test step 4.
- NOT OK - Battery cables are incorrect.
Repair: Clean the terminals or replace the terminals. Tighten the terminals.
Stop.
Test Step 4. TEST CABLES FROM THE BATTERY TO THE STARTING MOTOR FOR VOLTAGE DROP
- Attempt to crank the engine. Measure the voltage from "Mtr" terminal to ground.
Expected Result:
The battery voltage is less than the voltage in table 2.
Results:
- OK - The voltage drop is less than the specified voltage drop. Proceed to test step 5.
- NOT OK - The voltage drop is greater than the specified voltage drop.
Repair: Repair the cables or replace the cables. Repeat the voltage measurement. If the voltage remains low, measure the voltage drop across each component that is listed in table 2. Replace all components that are out of specification.
Stop.
Test Step 5. CHECK ENGINE ROTATION
- Remove the starter from the engine.
- Turn the engine by hand.
Expected Result:
The engine turns with normal effort.
Results:
- YES - The engine turns with normal effort. Proceed to test step 6.
- NO - The engine turns with more than normal effort. The engine needs to be serviced.
Repair: Repair the engine. Refer to the Disassembly and Assembly manual for the engine.
Stop.
Test Step 6. TEST THE START RELAY
- Locate the start relay for the starter.
- Attempt to crank the engine. Measure the resistance across the start relay.
Expected Result:
The resistance should be less than 5 ohms.
Results:
- OK - The resistance is less than 5 ohms. The start relay is correct. Proceed to test step 7.
- NOT OK - The resistance is greater than 5 ohms. The start relay has failed.
Repair: Replace the start relay.
Stop.
Test Step 7. TEST THE STARTING MOTOR SOLENOID
- Perform the starting motor solenoid test. See Testing and Adjusting, "Starting Motor Solenoid - Test".
Expected Result:
The solenoid is correct.
Results:
- OK - The solenoid is correct. Go to test step 8
- NOT OK - The solenoid is incorrect.
Repair: Replace the solenoid.
Stop.
Test Step 8. TEST THE INTERNAL COMPONENTS OF THE STARTING MOTOR
- Check starting motor brushes. See Testing and Adjusting, "Brush and Brush Holder - Check".
Expected Result:
The brushes of the starting motor are correct.
Results:
- OK - The brushes of the starting motor are correct.
Repair: Perform the component tests for the starting motor. See the proper test in the Testing and Adjusting section.
Stop.
- NOT OK - The brushes are incorrect.
Repair: Replace brushes or repair brushes. Repair the brush holder or replace the brush holder.
Stop.