What Causes the Car Key to Turn but the Engine Not to Start?

[OAmy]

When the car key can turn but the engine fails to start, it is typically due to a depleted battery, burnt-out relay, or a faulty electromagnetic switch. Below are the detailed explanations for each cause: Depleted Battery: A drained car battery or disconnected battery terminals, loose positive/negative terminal connections, or broken battery cables can prevent the engine from starting. Check if the battery is dead and recharge it promptly. Burnt-out Relay: Severely corroded starter relay contacts, an open-circuit relay coil, or a damaged electromagnetic switch in the starter (burnt contacts or a broken pull-in coil). Internal winding faults (open/short circuits) in the starter motor, a bent armature shaft, or excessively tight bearing clearance may also be culprits. Replace the relay immediately. Faulty Electromagnetic Switch: Severely burnt contacts or a broken pull-in coil in the starter’s electromagnetic switch. Internal winding faults (open/short circuits) in the DC motor, heavily corroded commutator, excessively worn brushes, stuck brushes in the holder, or weak brush springs. Visit a repair shop for replacement.