1. Fuel System:
* No Fuel: Check the fuel pump (listen for a whirring sound when the key is turned to "on" – but *not* cranking). Check the fuel filter (for clogs). Verify you have fuel in the tank. Check the fuel pressure at the rail with a gauge (should be within specs for your engine).
* Fuel Delivery Problems: Inspect the fuel lines for leaks or cracks. Check the fuel injectors (may require a fuel pressure gauge and/or a noid light to check for pulsing).
2. Ignition System:
* Spark: This is the most crucial aspect. You need a strong spark at each spark plug. Use a spark tester (a gap between two wires, that should jump when cranking) on each wire, one at a time. If no spark:
* Distributor Cap and Rotor: Inspect for cracks, carbon buildup, or corrosion. Replace if necessary.
* Ignition Coil: A bad coil won't produce enough voltage. Testing requires a multimeter or a coil tester.
* Ignition Module (or Control Module): This controls the coil firing. Often difficult to test without specialized equipment, but a faulty module is a common culprit.
* Cranking Speed: Is the engine cranking over fast enough? A weak battery or starter can prevent spark generation.
* Ignition Switch: Check if power is reaching the ignition system when the key is turned.
* Wiring: Check all wiring for breaks, shorts, or loose connections in the ignition system.
3. Computer/Sensor Problems (if equipped with a computer):
* Crankshaft Position Sensor (CKP): This sensor tells the computer where the engine is in its cycle. A faulty CKP will prevent firing.
* Cam Position Sensor (CMP): Similar to the CKP, but for the camshaft.
* Other Sensors: Numerous sensors (like MAP, TPS, etc.) can prevent the computer from allowing the engine to fire if their readings are out of range. Diagnosing these usually requires a scan tool to read fault codes.
4. Starting System:
* Battery: A weak or dead battery won't provide enough power to crank the engine or power the ignition system. Test the battery voltage.
* Starter: A bad starter won't crank the engine. Test the starter or have it tested.
Systematic Troubleshooting:
1. Check for fuel: Is there fuel in the tank, and does the pump work?
2. Check for spark: This is the most likely cause if the fuel system seems okay.
3. Check the battery and starting system: Ensure the engine cranks over adequately.
4. If spark is missing: systematically check the coil, distributor cap and rotor, ignition module, and wiring.
5. If you have spark and fuel, and still no start: Investigate computer-related problems (sensors, etc.). A code reader will be very helpful here.
Important Note: Working on a vehicle's ignition system involves high voltage. Be careful, disconnect the negative battery terminal before working on it, and use appropriate safety precautions. If you're not comfortable working on cars, take it to a mechanic. They have the tools and experience to diagnose the problem quickly and efficiently.
