1. Battery:
* Voltage Test: This is the *first* thing to check. Use a multimeter to measure the battery voltage. It should be around 12.6 volts when fully charged. Less than 12 volts indicates a weak battery. Try jumping it with a good battery to see if it cranks. If it does, replace the battery.
* Clean Terminals: Corroded battery terminals can prevent current flow. Clean them with a wire brush and baking soda and water solution. Make sure the connections are tight.
* Battery Cables: Check the cables for damage, looseness, or corrosion at both the battery and starter ends.
2. Starter Motor:
* Listen for a Click: When you turn the key, do you hear a single click? This often indicates a low battery, a bad starter solenoid, or a bad connection to the starter.
* Tap the Starter: (Use caution!) Gently tap the starter with a wrench or hammer while someone tries to crank the engine. Sometimes, a stuck solenoid can be freed this way. This is a temporary fix and doesn't address the underlying problem.
* Starter Solenoid: The solenoid is a part of the starter. A faulty solenoid won't engage the starter motor. It might require replacement.
* Starter Motor Itself: The starter motor itself could be failing. This often requires replacement.
3. Ignition System:
* Ignition Switch: A faulty ignition switch might not be sending power to the starter.
* Neutral Safety Switch (Automatic Transmission): Make sure the transmission is in Park (or Neutral if manual). A faulty neutral safety switch prevents the starter from engaging unless the transmission is in the correct gear.
* Wiring: Check for any broken or loose wires in the ignition system, particularly those leading to the starter and solenoid. Look for corrosion or damage.
4. Other Potential Issues:
* Security System (if equipped): Older vehicles sometimes had aftermarket security systems that could prevent starting.
* Fuse: Check the fuses related to the ignition and starter circuits.
Troubleshooting Steps:
1. Battery Voltage Test: This is the absolute *first* step.
2. Clean Battery Terminals and Cables: This is a simple fix that often solves the problem.
3. Listen for Clicks: Determine if it's a battery/solenoid issue or something else.
4. Check Neutral Safety Switch (Automatic): Ensure the transmission is in Park (or Neutral).
5. Inspect Wiring: Look for damage or corrosion.
6. Check Fuses: Eliminate this possibility.
If you're not comfortable working on your vehicle's electrical system, take it to a qualified mechanic. Incorrectly working on electrical systems can be dangerous. Providing more details about the sounds you hear when trying to crank the engine would help narrow down the possibilities.
