* Dead or Weak Battery: This is the most common cause. Even if the car cranks slowly, it might not have enough power to start the engine. Test the battery voltage.
* Bad Starter Motor: While cranking indicates the starter is *somewhat* working, a failing starter might not be providing enough power to turn the engine over fast enough for ignition. A clicking sound is a strong indicator of a failing starter.
* Faulty Ignition System: This includes:
* Ignition Coil: This provides the high voltage spark to ignite the fuel-air mixture. A faulty coil will prevent the engine from firing.
* Spark Plugs: Worn, fouled, or damaged spark plugs can prevent proper ignition.
* Ignition Wires (Spark Plug Wires): Damaged or loose wires can disrupt the spark.
* Crankshaft Position Sensor (CKP Sensor): This sensor tells the computer the position of the crankshaft, crucial for timing the spark. A faulty sensor will prevent ignition.
* Cam Position Sensor (CMP Sensor): Similar to the CKP sensor, but for the camshaft. A fault here also disrupts timing.
* Fuel System Problems:
* Empty or Low Fuel: Sounds obvious, but check the fuel gauge!
* Fuel Pump Failure: The fuel pump delivers fuel to the engine. A failing pump might not provide enough pressure.
* Fuel Filter Clog: A clogged fuel filter restricts fuel flow.
* Fuel Injectors: Clogged or faulty fuel injectors prevent fuel from being sprayed into the cylinders.
* Fuel Pressure Regulator: This regulates the fuel pressure; a malfunction can lead to insufficient pressure.
* Security System Issues: Some vehicles have immobilizers that prevent starting if they don't recognize the key or key fob.
* Engine Mechanical Problems:
* Broken Timing Belt/Chain: This is a serious issue that can cause the engine to not turn properly or at all.
* Low Compression: This indicates a problem with the engine's ability to create the pressure needed for combustion.
To diagnose the problem, you'll need to check some things yourself or take it to a mechanic. Testing the battery voltage is a good first step. If the battery is good, a mechanic can use diagnostic tools to pinpoint the exact cause. They can test the ignition system, fuel system, and check for any error codes stored by the car's computer.
