* Fuel System Problems:
* Empty or Low Fuel: The most obvious – check your fuel gauge and try adding fuel.
* Fuel Pump Failure: The pump might not be delivering fuel to the engine. You might hear a whirring sound from the fuel pump when you turn the key (sometimes you can hear this in the back of the car, near the fuel tank). If not, or if the sound is weak, the fuel pump is a suspect.
* Fuel Filter Clogged: A clogged filter restricts fuel flow.
* Fuel Injectors Clogged or Faulty: They may not be spraying fuel properly.
* Fuel Pressure Regulator Problems: This regulates fuel pressure; a malfunction can prevent proper fuel delivery.
* Ignition System Problems:
* Spark Plugs: Worn, fouled, or damaged spark plugs prevent ignition. Check their condition and replace if necessary.
* Spark Plug Wires: Cracked or damaged wires can prevent spark from reaching the plugs. Inspect for damage or cracks.
* Ignition Coil: This provides the high voltage for the spark plugs. A faulty coil won't produce sufficient spark.
* Crankshaft Position Sensor (CKP Sensor): This sensor tells the computer the engine's rotational position. A faulty sensor prevents the computer from sending the signal to fire the spark plugs at the right time.
* Camshaft Position Sensor (CMP Sensor): Similar to the CKP sensor, but for the camshaft. A problem here will also prevent proper timing.
* Ignition Module (Distributorless Ignition Systems): If your car uses a distributorless ignition system, the ignition module might be faulty.
* Ignition Switch: While less common, a failing ignition switch might not be sending power to the ignition system correctly.
* Other Possibilities:
* Security System: If your car has an aftermarket or factory alarm/immobilizer, it might be preventing the engine from starting.
* Low Battery Voltage: While the starter is turning, a weak battery might not provide enough power for the ignition system to function correctly. Test the battery voltage.
* Engine Control Module (ECM) Problems: The computer that controls the engine might be malfunctioning. This is a less likely but possible cause.
Troubleshooting Steps:
1. Check the obvious: Fuel level, battery voltage.
2. Listen carefully: Do you hear the fuel pump prime when you turn the key?
3. Check spark: With the spark plug wires disconnected (be careful!), ground them against the engine block and crank the engine. Look for a strong spark. (Do this with caution and be aware of high voltage)
4. Check the fuses and relays related to the fuel pump and ignition system. Consult your owner's manual for their locations.
If you're not comfortable working on your car yourself, take it to a mechanic for diagnosis. They have the tools and expertise to pinpoint the problem accurately. Providing them with the information that the engine turns over but doesn't start will help them narrow down the possibilities quickly.
