1. Check the obvious (but important):
* Battery connections: Make absolutely sure the battery terminals are clean, tight, and corrosion-free. A seemingly good battery can fail to deliver power due to poor connections. Clean them with a wire brush and baking soda and water solution, then apply dielectric grease.
* Battery voltage: Use a multimeter to check the battery voltage directly at the terminals. It should be around 12.6 volts when not cranking. If significantly lower, even with a "good" battery, it might be failing.
* Grounding: A poor ground connection can prevent the starter from receiving power. Trace the main ground cable from the battery (usually negative) to the engine block. Ensure it's clean, tight, and has a good connection. Check other ground straps as well.
2. Check the Starting Circuit:
* Ignition Switch: A faulty ignition switch is a common culprit. Try wiggling the key while attempting to start. A weak or intermittent connection within the switch could be the problem.
* Starter Relay/Solenoid: This is a common failure point. Located near the starter motor, it's an electromagnetic switch that engages the starter motor when you turn the key.
* * Listen for a click: When you turn the key, do you hear a *click* from the starter relay? One click usually means the relay is working, but may have issues supplying the current to the starter motor. Multiple clicks can indicate a weak or failing relay. No click indicates a relay problem or problem before the relay.
* * Jump the Solenoid (CAUTION): With the key OFF, carefully use jumper cables to bypass the solenoid. Connect one end to the large terminal on the solenoid (connected to the battery cable), and the other end to the smaller terminal (usually with a smaller gauge wire). This bypasses the solenoid. Try to crank the engine. If it cranks, the solenoid is the most likely culprit. Be careful, the engine could crank even with the key off when using this method.
* Starter Motor: If the solenoid seems good, the starter motor itself might be bad. This would require removing the starter to test it or replace it. This is usually a mechanically difficult task and may require a professional mechanic.
* Wiring: Visually inspect the wiring between the battery, ignition switch, starter relay/solenoid, and starter motor for any damage, corrosion, or loose connections. Pay close attention to the heavy gauge wires.
3. Other possibilities (less likely but still worth considering):
* Neutral Safety Switch: On an automatic transmission, this switch prevents starting unless the transmission is in Park or Neutral. If it's faulty, the starter won't engage.
* Wiring harness issues: A break or short in the main harness could affect the entire system. This is a difficult problem to diagnose.
* Ignition system problems: While less likely to directly prevent cranking, problems in the ignition system (distributor, coil, etc.) could sometimes manifest as a no-crank condition.
Troubleshooting Strategy:
Start with the simplest checks (battery connections, grounding). If those are okay, move on to the starter relay/solenoid. Jumping the solenoid is a great way to isolate this component. If all else fails, a qualified mechanic will need to diagnose the problem. Trying to test or replace parts without sufficient knowledge can lead to damage or injury.
