You get in your car; turn the ignition key and all you hear is a clicking sound. This means you have an issue with the starter motor or starter solenoid. Diagnosing the issue by how the car reacts to being started or by the sound the car makes when you try to start it is just about impossible. The best way to determine which component is bad is to short out the starter. With this method, you eliminate the starter from the circuit and send power directly from the battery to the starter motor.
Locate the starter motor under the vehicle. The solenoid bolts to the starter, and the starter typically bolts to the bell housing or transmission housing. It is approximately 8 inches in length and tubular in shape, with several wires extending out of it.
Identify the two metal lugs on the back of the starter solenoid. The lug on the left has a large wire that extends to the ignition. The lug on the right has a jumper wire that goes down to the metal casing on the starter motor.
Place the metal portion of a screwdriver across both lugs. This will short out the solenoid and eliminate it from the circuit so the starter motor has a direct connection to the ignition and to the battery.
Hold the screwdriver in place while a second person attempts to start the vehicle. Because the screwdriver has shorted out the solenoid, the engine will not start. Listen to the starter motor. The motor inside the starter should turn on and have a consistent hum. If the motor makes a crackling sound or does not turn on at all, replace the starter. If the starter runs smoothly, replace the solenoid.
Make sure you have the parking brake set on the vehicle when you perform this test. Also, expect some sparks when you short out the starter. This is normal and will not hurt you, provided you only touch the insulated portion of the screwdriver.