* Spark: A lack of spark is a common reason. Check these:
* Spark Plugs: Inspect them for wear, fouling (black sooty deposits), or damage. They might need replacing or cleaning.
* Spark Plug Wires: Look for cracks, fraying, or loose connections. A faulty wire can prevent spark from reaching a plug.
* Ignition Coil(s): The coil(s) provide the high voltage for the spark plugs. A faulty coil will prevent or weaken the spark. This often manifests as misfires or no start in one or more cylinders.
* Ignition Control Module (ICM) / Crankshaft Position Sensor (CKP) / Cam Position Sensor (CMP): These are electronic components that control the ignition timing. A fault in any of these can prevent a spark. Diagnosis usually requires a mechanic or OBD-II scanner.
* Air Intake System:
* Air Filter: A severely clogged air filter restricts airflow, preventing proper combustion. Replace it if it's dirty.
* Air Intake Hoses: Check for leaks or disconnections in the hoses leading to the engine.
* Compression:
* Low Compression: This means the engine isn't creating enough pressure to ignite the fuel-air mixture. This often requires a compression test by a mechanic to diagnose. Possible causes include worn piston rings, valve problems, or head gasket issues.
* Timing:
* Timing Belt/Chain Issues: A broken or severely slipped timing belt or chain will prevent the engine from firing. This is a serious issue that requires professional attention.
* Security System:
* Immobilizer: Some cars have immobilizer systems that prevent starting if they don't recognize the key or there's a fault in the system. Try a different key if possible.
Troubleshooting Steps:
1. Check for error codes: Use an OBD-II scanner to read any diagnostic trouble codes (DTCs) stored by the car's computer. These can pinpoint the problem.
2. Listen carefully while cranking: Do you hear any unusual sounds (clicking, ticking, grinding)? This can provide clues.
3. Visual Inspection: Check all the components mentioned above visually for obvious problems.
4. Test the spark: A simple way to check for spark is to remove a spark plug wire, ground the end of the wire to the engine block, and crank the engine. You should see a spark jump the gap. (Be careful; high voltage!)
If you're not comfortable working on your car's electrical system or engine, take it to a mechanic. Incorrect diagnosis and repair attempts can cause further damage. Provide them with the information that the fuel pump is working and the car cranks but doesn't start.
