DIAGNOSE ENGINE DOES NOT CRANK

by Kyle McFadden

SYMPTOM SUMMARY
The engine fails to crank over.

USUAL CAUSE
This symptom is usually a result of a defect in the electrical system. It is usually a result of a drained battery, defective starter, or a defect in the ignition switch circuitry.

DIAGNOSIS
The first step in the diagnosis is an inspection of the fuses. Refer to the fuse box placard and owner’s manual for fuse ratings and designations. Some vehicles use fusible links that are at or near the batteries positive battery cable. These fusible links are designed to open when an electrical overload is present. They will not reset and will require replacement when blown. An inspection of the fusible links should be performed. Clean the battery terminals using a wire brush. Ensure that the inside of the battery terminal and posts are clean and free from corrosion. You should ensure the vehicle has a fully charged battery. Attempt to jump start the vehicle. If the vehicle cranks, a functional check of the battery and charging system should be performed. Refer to the “Battery Goes Dead” or “Battery or Charge Light On” articles for further diagnosis. If the engine will not jump start, a defect in the starter or ignition circuit is the most probable cause. Using a voltmeter, measure the voltage on the small wire of the starter solenoid while an assistant cranks the vehicle. If voltage is present, the most likely cause is a defective starter. If there is no voltage present, a defect in the ignition switch or circuitry is indicated. Refer to a vehicle specific wiring diagram and service manual for specifics on diagnosing the ignition switch circuitry.

PRECAUTIONS, TIPS, and NOTES
Use caution when working around hot or rotating engine parts. When using test equipment, refer to the manufacturers instructions for proper usage.

(Kyle has an affinity for Pale Ale and tooling on his 1956 Chevrolet Nomad Station Wagon.)