I. Fuel System:
* Empty Tank: The most obvious – check your fuel gauge and, if unsure, add some fuel.
* Fuel Pump: The pump might be failing to deliver fuel to the carburetor or fuel injectors. You can listen for the pump's hum when you turn the ignition key to the "on" position (before cranking). A lack of humming suggests a problem.
* Fuel Filter: A clogged fuel filter will restrict fuel flow. It's relatively inexpensive and easy to replace.
* Clogged Carburetor (if carbureted): If it's a carbureted model, the carburetor might be clogged, causing fuel starvation. This requires cleaning or rebuilding.
* Fuel Injector Issues (if fuel injected): A fuel injector could be clogged or failing. This often requires specialized tools and knowledge to diagnose.
* Fuel Pressure: Low fuel pressure prevents proper fuel delivery. A fuel pressure gauge is needed to check this.
II. Ignition System:
* Distributor Cap and Rotor: Cracks or corrosion in the cap and rotor can prevent a spark from reaching the spark plugs. Inspect for damage.
* Spark Plugs and Wires: Worn, fouled, or damaged spark plugs or wires will prevent ignition. Check the gap on the plugs and inspect for damage.
* Ignition Coil: A failing ignition coil won't produce the high voltage needed for sparking. This often requires testing with a multimeter.
* Ignition Module (or Electronic Ignition Control Unit - EICU): This controls the ignition timing and spark. Failure is less common but possible. Testing usually involves a multimeter or specialized diagnostic equipment.
* Distributor Problems: Worn bushings, timing chain issues or the distributor itself failing can disrupt the ignition signal.
* Cranking Speed: The engine may not be turning over fast enough to create sufficient spark. A weak battery or starter motor are possible causes here.
III. Other Possibilities:
* Crankshaft Position Sensor (CKP Sensor): This sensor is essential for the computer to know the engine's rotational position to trigger ignition. A faulty sensor will prevent starting.
* Battery/Charging System: A weak battery or faulty alternator can prevent the engine from starting reliably.
* Computer/ECU Issues (if fuel injected): While less common, a faulty computer can prevent the engine from starting. Diagnosis usually requires specialized equipment.
Troubleshooting Steps:
1. Check the obvious: Fuel level, battery voltage, obvious visual inspection of wires, connections, and components.
2. Listen for the fuel pump: Does it prime when you turn the key on?
3. Check for spark: Remove a spark plug, ground it to the engine block, and crank the engine. Look for a strong spark.
4. Test the ignition coil: Use a multimeter to test the coil's primary and secondary resistance.
5. Check the distributor cap and rotor: Look for cracks or corrosion.
If you're not comfortable working on your car's electrical system or fuel system, take it to a qualified mechanic. Attempting repairs without the proper knowledge and safety precautions can be dangerous. The more details you can provide about symptoms (e.g., is there backfiring, unusual smells, etc.) the more a mechanic can diagnose the issue.
