Common Causes:
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position. A faulty CKP prevents the engine from starting because the computer can't determine the timing for fuel injection and ignition. This is a very common cause of no-start conditions.
* Cam Position Sensor (CMP): Similar to the CKP, but monitors the camshaft's position. A faulty CMP will also prevent the engine from starting due to incorrect timing.
* Fuel Pump Relay or Fuel Pump: The fuel pump might be failing, or the relay that controls it might be bad. This will result in no fuel being delivered to the engine. You might hear the fuel pump prime briefly when you turn the key to the "on" position – if you don't hear anything, this is a strong possibility.
* Ignition System: This includes the ignition coil(s), spark plug wires, and spark plugs. A faulty component here will prevent the engine from igniting the air/fuel mixture. Weak or failing spark plugs are a common culprit.
* Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A dirty or faulty MAF can cause a lean condition, leading to the engine stalling and refusing to restart.
* Battery/Alternator: A weak battery or a failing alternator can prevent the engine from starting, especially if the battery is low. Check the battery voltage with a multimeter.
Less Common, but Still Possible Causes:
* Computer (PCM): A faulty PCM can cause a variety of issues, including no-start conditions. This is less likely than the other possibilities.
* Security System: If the car has an aftermarket or factory immobilizer, a problem with the system could prevent starting.
* Wiring Issues: Damaged or corroded wiring anywhere in the system can disrupt electrical signals, preventing the engine from starting. Focus on the wiring harness related to the sensors mentioned above.
* Fuel Filter: A clogged fuel filter can restrict fuel flow.
* Throttle Position Sensor (TPS): While less likely to cause a complete no-start, a faulty TPS can sometimes contribute.
Troubleshooting Steps:
1. Check the obvious: Battery voltage, listen for fuel pump priming.
2. Check for error codes: Use an OBD-II scanner to retrieve any diagnostic trouble codes (DTCs) stored in the PCM. These codes can point directly to the problem.
3. Visual inspection: Inspect the spark plugs, wires, and other easily accessible components for signs of damage or wear.
4. Test components: Use a multimeter to test the CKP, CMP, MAF, and other sensors for proper voltage and resistance. This requires some basic automotive electrical knowledge or a repair manual.
5. Check fuel pressure: If you suspect a fuel delivery problem, you'll need a fuel pressure gauge to measure the pressure.
If you're not comfortable working on your car yourself, take it to a qualified mechanic for diagnosis and repair. The "no start" condition can have many causes, and accurate diagnosis often requires specialized tools and expertise. Remember to always disconnect the negative battery terminal before performing any electrical tests.
