Ignition System Problems:
* Spark Plugs: Worn, fouled (covered in oil or carbon), or damaged spark plugs prevent a spark, crucial for ignition. Check their condition and replace if necessary. Gap may also be incorrect.
* Spark Plug Wires: Damaged, loose, or corroded wires can interrupt the electrical signal to the spark plugs. Inspect for cracks, damage, or poor connections.
* Ignition Coil: This component boosts the voltage to create the spark. A faulty coil can prevent sparks or produce weak ones.
* Distributor (if applicable): Older cars have distributors. Issues here can include a faulty rotor, cap, or internal components.
* Crankshaft Position Sensor (CKP) or Cam Position Sensor (CMP): These sensors tell the computer the engine's rotational position, essential for proper timing of the spark. A faulty sensor will prevent starting.
* Ignition Switch: A failing ignition switch might not be sending enough power to the ignition system.
* Computer/ECU Problems: Rare, but a faulty Engine Control Unit (ECU) can prevent the engine from starting, even if everything else seems fine.
Fuel Delivery Problems:
* Fuel Pump: A failing fuel pump can't deliver enough fuel to the engine. You might hear a faint whirring sound when you turn the key if it's struggling, but often it's silent.
* Fuel Filter: A clogged fuel filter restricts fuel flow.
* Fuel Injectors: Clogged or faulty fuel injectors can prevent fuel from being sprayed into the combustion chamber.
* Fuel Pressure Regulator: This regulates fuel pressure. A faulty regulator can cause low fuel pressure or leaks.
* Empty or Low Fuel Tank: Sounds obvious, but sometimes overlooked!
Other Possibilities:
* Security System: An anti-theft system could be preventing the engine from starting.
* Starter Motor (though unlikely if it cranks): While you say it cranks, a weak starter *could* still be barely providing enough power. If the cranking is unusually slow or weak, this could be a contributing factor.
* Battery: A weak battery might have enough juice to crank the engine but not enough to power the ignition system effectively. Have the battery tested.
* Alternator (though unlikely if it cranks): A bad alternator won't directly prevent starting, but a completely dead battery *because* of a bad alternator will.
Troubleshooting Steps:
1. Check the obvious: Fuel level, battery voltage (use a multimeter), and listen for any unusual noises.
2. Listen carefully during cranking: A weak cranking sound usually indicates a battery or starter issue, a whirring sound could be the fuel pump.
3. Check the spark plugs: Remove a spark plug, attach it to the wire, ground it to the engine, and crank the engine to see if you get a spark. (Be careful not to touch the metal parts.)
4. Check fuel pressure (requires a fuel pressure gauge): Measure the fuel pressure to ensure the fuel pump and injectors are working correctly. This is best left to a mechanic.
If you're not comfortable working on your car, take it to a mechanic. They have the tools and expertise to diagnose the problem quickly and efficiently. Providing them with the information that it cranks but doesn't start is a good starting point.
