If the starter motor does not turn when the switch is operated, first check the shift lever (for automatic transmission) or clutch pedal (for manual transmission). Ensure the battery is charged and all cables are securely connected. If the motor spins but the engine does not crank, the starter motor may need to be replaced. If the solenoid clicks but the motor does not operate, the issue may be with the battery, solenoid contacts, or starter motor. If the solenoid plunger cannot be heard, it may be defective or there may be an open circuit. To check the solenoid, connect a jumper lead between the battery and "S" terminal. If the motor operates, the solenoid is fine. If not, remove the starter/solenoid assembly for testing and repair. If the motor cranks slowly, check the battery and terminal connections. If the engine is partially seized or has the wrong oil, it may crank slowly. To diagnose further, run the engine until normal temperature, then stop and disconnect the coil wire. Connect a voltmeter to the starter motor terminal and ground. Crank the engine and take voltmeter readings. A reading of 9 volts or more at normal cranking speed is normal. If the reading is less than 9 volts and the cranking speed is slow, the solenoid contacts may be burned.