I. Ignition System:
* Dead Battery: The most common cause. Test the battery voltage with a multimeter. Should be around 12.6V when fully charged. A lower voltage indicates a weak or dead battery.
* Bad Battery Cables: Corroded or loose battery terminals can prevent current flow. Clean them thoroughly with a wire brush and baking soda/water solution.
* Faulty Starter: The starter motor cranks the engine. If you turn the key and hear a click or nothing at all, the starter might be bad, or its connections faulty. You might hear a "solenoid click" (a single loud click) which indicates a problem with the starter motor itself or its connections.
* Ignition Switch Problems: A malfunctioning ignition switch can prevent power from reaching the starter or other essential components.
* Ignition Coil: This component provides the high voltage needed for spark plug ignition. A faulty coil will prevent the engine from firing.
* Distributor Cap and Rotor: These components distribute high voltage to the spark plugs. Worn or cracked parts can cause misfires or no spark. Check for cracks, corrosion, or excessive wear.
* Spark Plugs and Wires: Worn, fouled, or damaged spark plugs and wires will prevent proper ignition. Inspect for cracks, corrosion, or excessive wear. Gap should be correct.
II. Fuel System:
* Empty Fuel Tank: Obvious, but easily overlooked.
* Fuel Pump Failure: The fuel pump delivers fuel from the tank to the engine. A faulty pump will prevent fuel from reaching the carburetor or fuel injectors. Listen for the pump humming when the key is turned to "on" (but not started).
* Clogged Fuel Filter: A dirty fuel filter restricts fuel flow.
* Fuel Injector Issues (if fuel injected - less likely on a '86): Clogged or faulty injectors will prevent fuel from reaching the combustion chamber. (More common in later fuel-injected models, but possible.)
* Carburetor Problems (if carbureted): If it's carbureted, the carburetor might be clogged, need adjustment, or have a faulty choke.
III. Other Potential Problems:
* Security System (if equipped): An aftermarket security system could be interfering.
* Neutral Safety Switch: This switch prevents the engine from starting unless the transmission is in park or neutral. Check to ensure the gear selector is in the correct position.
* Sensor Issues: Various sensors (e.g., crankshaft position sensor, coolant temperature sensor) can prevent the engine from starting if they malfunction. These are less likely to be the primary cause on an older vehicle, but possible.
* Alternator Issues: While not directly preventing starting, a failing alternator might prevent the engine from running *after* it starts. Test the alternator's output voltage.
* Broken Timing Belt (catastrophic): A broken timing belt will render the engine unable to start, and may cause significant internal engine damage.
Troubleshooting Steps:
1. Check the obvious: Battery, fuel level, and if the gear selector is in Park or Neutral.
2. Listen carefully: Pay close attention to any sounds (clicking, humming) when you turn the key.
3. Visual inspection: Check for loose or corroded connections, damaged wires, and worn components.
4. Start simple: Check the battery and cables first.
5. Use a multimeter: This tool is essential for checking voltage and other electrical components.
6. Consult a repair manual: A Haynes or Chilton manual for your specific year and model will provide detailed diagrams and troubleshooting information.
If you are not comfortable working on your vehicle yourself, it's best to take it to a qualified mechanic for diagnosis and repair. Many of these issues require specialized tools and knowledge to properly diagnose.
