1. Ignition System:
* Ignition Switch: This is a common culprit. It might be failing to send power to the starter motor. Try jiggling the key while attempting to start. If it starts intermittently, the switch is likely bad.
* Starter Motor: The starter itself could be failing. It might be getting power but not engaging the flywheel to crank the engine. You might hear a clicking sound when you turn the key – this is often a sign of a weak starter or a bad connection.
* Ignition Coil: This part provides the high voltage needed for the spark plugs. A faulty coil will prevent the engine from firing.
* Spark Plugs and Wires: Worn or fouled spark plugs or damaged wires will prevent a spark, leading to a no-start condition. Check for cracks or corrosion on the wires and visually inspect the plugs.
* Distributor (if equipped): Older vehicles often have distributors. Check the cap and rotor for cracks or corrosion. A faulty distributor can disrupt the spark timing.
2. Fuel System (despite having gas):
* Fuel Pump: Even with gas in the tank, a faulty fuel pump might not be delivering fuel to the engine. You might hear the pump whirring when you turn the key (listen closely near the fuel tank). If not, it could be failing.
* Fuel Filter: A clogged fuel filter can restrict fuel flow. It's relatively inexpensive and easy to replace.
* Fuel Injectors (if fuel-injected): Problems with injectors can prevent fuel from reaching the combustion chambers. This requires more advanced diagnostics.
3. Other Possibilities:
* Neutral Safety Switch (Automatic Transmission): Prevents the car from starting unless the transmission is in Park or Neutral. Check if the transmission is correctly positioned.
* Security System (if equipped): Some older cars had aftermarket or factory security systems that could disable starting if a problem is detected.
* Loose or Corroded Connections: Check all battery terminals, starter connections, and other electrical connections for corrosion or looseness. Clean them with a wire brush and apply dielectric grease.
Troubleshooting Steps:
1. Listen Carefully: When you turn the key, do you hear anything (clicking, whirring, nothing)? The sounds give clues.
2. Visual Inspection: Look for any obvious problems – loose wires, corroded connections, etc.
3. Check for Spark: A simple way (if you're comfortable working with electricity) to test for spark is to remove a spark plug wire, ground the metal end of the wire to the engine block, and crank the engine. A strong spark should jump the gap. Caution: This involves high voltage and should only be done with the ignition system turned off and the battery disconnected.
4. Check Fuel Pressure (Advanced): This requires a fuel pressure gauge and some mechanical knowledge. It's a more definitive way to check if the fuel pump is working properly.
If you're not comfortable working on the car yourself, it's best to take it to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately and efficiently. Providing them with the information about the sounds you hear when you try to start it will be helpful.
