Detroit Diesel Troubleshooting Diagrams

To determine if a defective starter is causing no start, perform the following steps: ‪

1. Place the red lead of a voltmeter to the solenoid “BAT” or terminal;

1. Red Lead ‪
2. Starter Ground ‪
3. Solenoid Terminal ‪
4. Black Lead ‪
5. Voltmeter ‪

2. Place the black voltmeter lead to the starter ground terminal;
3. Engage the starter switch.
4. View the voltage reading on the meter.

1. If the voltage is less than specification (refer to OEM guidelines) while cranking the engine, starter replacement is necessary;
2. If the voltage is to specification (refer to OEM guidelines) while attempting to crank the engine, check for internal damage;

Starter Replacement

Perform the following steps for starter replacement: ‪

1. Replace the starter;
2. Verify replacement of starter;

‪

To determine if a defective magnetic switch is causing no start: ‪

1. Start engine.
2. Clamp a heavy gage battery jumper cable between the two large studs of the magnetic switch;

Basic Cranking Circuit

1. If the engine cranked with the jumper cable in place, the magnetic switch must be replaced; refer to section .
2. If the engine did not crank with the jumper cable in place, check the starter.

Magnetic Switch Replacement

Perform the following steps for magnetic switch replacement: ‪

1. Replace the magnetic switch. Refer to OEM guidelines.
2. Perform verification of magnetic switch replacement;

Test Engine with New Magnetic Switch

Perform the following steps to determine if the magnetic switch replacement resolved the no start condition:

Attempt to start and run the engine.
1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
2. If the engine fails to start or run, check the starter;

To determine if a discharged battery is causing the engine not to start, perform the following steps: ‪

Measure and record the voltage at the battery terminals; refer to OEM guidelines.

1. If the voltage recorded is below OEM specifications and the engine failed to start, replacement is necessary;.
2. If the voltage recorded is at recommended OEM specifications and the engine failed to start, check the magnetic switch;

Discharged Battery Resolution

Perform the following steps for battery replacement: ‪

1.Replace the battery; refer to OEM guidelines.
2. Verify replacement of the battery.

Test Engine with New Battery

Perform the following steps to determine if the new battery resolved the no start condition: ‪

Attempt to start and run the engine.

1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
2. If the engine fails to start or run, check the magnetic switch.