When turning the ignition to start, a loud grinding sound is heard and the engine does not turn over. The most likely cause is

• A. Defective starter drive
• B. Worn timing belt
• C. Faulty ignition coil
• D. Bad battery terminal connection

Answer: (A)

When you hear a loud grinding sound as you turn the key and the engine doesn’t turn over, the likely issue is with the starter drive not engaging the flywheel properly. The starter motor spins to crank the engine, and its drive gear (pinion) must mesh smoothly with the teeth on the flywheel. If that gear is worn, damaged, or not being pushed into mesh correctly by the starter solenoid, it grinds against the flywheel teeth instead of engaging, so the crank doesn’t rotate and you hear a grinding noise.

Other possibilities don’t fit the symptom as well. A worn timing belt affects valve timing and can prevent starting, but it doesn’t cause a grinding engagement sound during crank. A faulty ignition coil affects spark, not the mechanical engagement of the starter. A bad battery terminal connection can prevent the starter from getting enough current and might cause slow cranking or a click, but it wouldn’t produce a loud grinding when you try to start.