1. Fuel System:
* Empty Tank: Sounds obvious, but check your fuel gauge and consider whether it's accurate. Low fuel can cause intermittent starting issues.
* Fuel Pump: Listen carefully near the fuel tank while someone cranks the engine. You should hear a whirring sound from the fuel pump for a second or two when the key is first turned to the "on" position (before cranking). No sound suggests a faulty pump, relay, or fuse.
* Fuel Filter: A clogged fuel filter restricts fuel flow. This is a relatively inexpensive and easy part to replace.
* Fuel Pressure: This requires a fuel pressure gauge to check the pressure at the fuel rail. Low pressure indicates problems with the pump, filter, regulator, or lines.
* Fuel Injectors: While less common as an initial problem, clogged or faulty injectors can prevent fuel from reaching the cylinders. This usually requires specialized tools and knowledge to diagnose.
2. Ignition System:
* Spark Plugs & Wires: Check the spark plugs for wear, fouling (covered in black soot or oil), or damage. Inspect the spark plug wires for cracks or damage; ensure they're securely connected. A weak spark can prevent starting.
* Distributor Cap and Rotor: Inspect the distributor cap and rotor for cracks, carbon tracking, or corrosion. These components distribute the high voltage to the spark plugs. Replacing them is relatively inexpensive.
* Ignition Coil: The coil provides the high voltage for the spark. A failing coil may provide weak or inconsistent spark.
* Ignition Module (Computer): This is a more advanced component, and testing it usually requires specialized tools or a mechanic. A failing ignition module can prevent the coil from functioning correctly.
* Cranking Sensor/Distributor Sensor (depending on engine type): These sensors tell the computer the engine is turning and to send spark. Failure can prevent starting.
3. Other Potential Issues:
* Battery: Though it cranks, a weak battery might not provide enough power for the ignition system and fuel pump. Check the battery voltage with a voltmeter.
* Alternator: While this doesn't directly prevent starting, a faulty alternator could have drained the battery over time.
* Starter Relay: Ensure the starter relay is functioning correctly. A bad relay prevents the starter from engaging even if the battery is good.
* Security System (if equipped): Some older cars had aftermarket or factory security systems that could prevent starting if the system is triggered.
* Computer Issues: A malfunctioning computer can prevent the engine from starting. This is usually a last resort and requires diagnostic tools.
Troubleshooting Steps:
1. Start with the basics: Check fuel level, battery voltage, and obvious visual checks of the spark plugs and wires.
2. Listen for the fuel pump: Does it prime when you turn the key on?
3. Check fuses and relays: Ensure all related fuses and relays are intact and functioning.
4. Visual inspection: Look for any obvious signs of damage or corrosion in the engine bay.
5. If you're not mechanically inclined, take it to a mechanic: Attempting advanced diagnostics without the proper tools and knowledge can lead to further damage.
Remember safety first! Disconnect the battery negative terminal before working on any electrical components. If you're uncomfortable working on your car, it's best to take it to a qualified mechanic. Providing the engine type (e.g., 305 V8, 2.8L V6) will help narrow down the potential problems.
