* Fuel System Issues:
* Empty or Low Fuel: The most obvious, but worth checking first.
* Fuel Pump Failure: The pump might not be sending fuel to the engine. You might hear a whirring sound from the fuel pump when you turn the key if it's failing.
* Clogged Fuel Filter: Restricts fuel flow.
* Fuel Injector Problem: Injectors might be clogged, faulty, or not receiving the signal to spray fuel.
* Fuel Pressure Regulator: Regulates fuel pressure; a faulty one can cause low pressure or leaks.
* Ignition System Issues:
* Spark Plugs: Worn, fouled, or damaged spark plugs prevent ignition.
* Spark Plug Wires: Cracked, damaged, or loose wires can disrupt the spark delivery.
* Ignition Coil: Supplies high voltage to the spark plugs; a faulty coil will prevent sparking.
* Crankshaft Position Sensor (CKP) or Cam Position Sensor (CMP): These sensors tell the computer the engine's position; a faulty sensor prevents proper fuel/spark timing. This is common on older vehicles.
* Ignition Control Module (ICM): This controls the ignition system; failure here can cause no spark.
* Other Potential Issues:
* Security System: An aftermarket or factory alarm or immobilizer might be preventing the engine from starting.
* Computer/ECM Problems: The engine control module (ECM) could be faulty. This is less common but possible.
* Low Battery Voltage (Even if cranking): While it cranks, the battery might not have enough power to consistently run the fuel pump and ignition system. Test the voltage.
Troubleshooting Steps:
1. Check the obvious: Fuel level, listen for the fuel pump (key on, engine off).
2. Check for spark: A simple spark tester on a spark plug wire will quickly tell you if you have spark.
3. Check fuel pressure: A fuel pressure gauge is needed to verify proper fuel pressure. This often requires a mechanic.
4. Check codes: Use an OBD-II scanner to retrieve any diagnostic trouble codes (DTCs) stored in the ECM. These codes can point directly to the problem.
Without more information (e.g., any unusual noises, smells, check engine light status), it's impossible to pinpoint the exact cause. A mechanic will be able to diagnose the problem more accurately and efficiently.
