* Dead battery (unlikely if it's cranking): While a weak battery might *prevent* cranking, if it's turning over strongly, the battery itself is probably not the primary culprit. However, a failing battery might not deliver enough power to the ignition system under load.
* Faulty starter motor (unlikely if it's cranking): A problem with the starter could prevent the engine from turning over. Since it's turning, the starter isn't likely the problem.
* Fuel delivery problems:
* Empty fuel tank: Seems obvious, but worth checking.
* Fuel pump failure: The pump might not be delivering fuel to the engine.
* Clogged fuel filter: A blocked filter prevents fuel from reaching the engine.
* Bad fuel injectors: These spray fuel into the cylinders; if they're clogged or malfunctioning, the engine won't start.
* Low fuel pressure: The fuel system might not be supplying enough pressure to the injectors.
* Ignition system problems:
* Spark plug issues: Worn, fouled, or damaged spark plugs prevent ignition.
* Spark plug wires: Damaged or loose wires can interrupt the spark.
* Ignition coil failure: The coil provides the high voltage needed for the spark plugs. A faulty coil will prevent sparking.
* Crankshaft Position Sensor (CKP) or Cam Position Sensor (CMP) failure: These sensors tell the computer the engine's position to time the ignition correctly. A faulty sensor will prevent proper timing and starting.
* Ignition control module (ICM) failure: This module controls the ignition system.
* Distributor cap and rotor (older vehicles): These components distribute the high voltage to the spark plugs. Wear or damage can disrupt sparking.
* Other possible causes:
* Security system issues: An immobilizer or alarm system might be preventing the engine from starting.
* Faulty alternator: While it won't directly stop the engine from starting, a bad alternator can cause issues if the battery is already weak.
* Computer problems (Engine Control Module/ECU): A fault in the engine's computer can prevent it from starting, though this is less common.
To diagnose the problem, you'll likely need a mechanic or at least a multimeter to check voltage and test components. Simply checking basic things like fuel level and obvious damage to wires is a good first step.
