The solenoid on a Briggs and Stratton engine acts as a fuse between the ignition switch and the engine starter. When the key is in the ON position, the electrical current flows to the solenoid and then on to the starter on the engine. If the solenoid becomes damaged, the engine will no longer turn over. Testing the solenoid is the first step in troubleshooting an engine that will not start. Knowledge of engine theory will help in this procedure,which will take 15 minutes to complete.
Place the engine on a hard, flat surface. To locate the solenoid on the engine, follow the positive (red) wire coming from the battery; it will lead into the solenoid.
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Remove the spark plug wire from the spark plug. Clean any corrosion off the battery terminals. Turn the key to the ON position and turn on the voltmeter. Place the negative lead from the voltmeter to the negative post on the battery. Place the positive lead (red) lead to the post on the solenoid that has the positive lead screwed on to it. Check the reading on the voltmeter; the reading should be 12 volts. If there is no voltage, tighten the bolt on the positive cable on the battery; tighten the nut on the solenoid.
Keep the negative lead from the voltmeter connected to the negative battery post. Place the positive lead from the voltmeter to the other post on the solenoid. Turn the key to the OFF position and then turn it to the ON position, while checking the voltmeter. If the voltmeter reads 12-volts while in the ON position and no voltage in the OFF position the solenoid is not defective. If no voltage is present in both the ON and OFF position, the solenoid is defective.