Cranking Speed Test

NOTE: Cranking speed is critical for a diesel engine to start, whether the engine is hot or cold. Some tachometers are not accurate at cranking speed. An alternate method of testing cranking speed or determining the accuracy of tachometer is to use a scan tool.

1. Remove the fuel solenoid fuse.
2. Install the digital tachometer to be tested (if desired).
3. Install the scan tool.
4. Crank the engine for 2 or 3 seconds in order to allow the starter to reach full speed.
5. Observe the engine RPM reading on the scan tool.
6. The minimum cranking speed is 100 cold and 180 hot. The actual cranking speed needed will vary depending on the condition of the engine (compression) and nozzles.