1. Check the battery. Check for a loose connection. Remove the corrosion on the terminals, if any.
2. Check the switch. Make sure there are no loose connections and check with a test light if the switch is any good.
3. Check battery for charge. It must have atleast 12 volts. If battery is dead and you charge it for and hour or two and it still does not have 12 volts, the battery is bad and must be replaced.
4. Check the starter. If the battery is good, check the voltage to the starter by taking a volt meter and grounding the black probe to a good ground and touching the red probe to the starter terminal. Turn the key. If all 12 volts are going to the starter and the engine still will not crank, then starter must be repaired. If less than 12 volts are going to the starter, check for exposed areas in the wiring which could cause a partial ground or corrosion. Remove the corrosion, if any, and tape up the wire with electrical tape.
5. Check the starter solenoid. After all the above checks have been done, finally check the starter solenoid. To check the solenoid, remove the wire from spade terminal. With a screw driver, touch the spade terminal and the hot side of the solenoid. If the starter turns, the starter solenoid is good and there is a problem in the safety switches. The solenoid is usually located on the back side of the accessories panel, in the engine compartment, on Riders and Tractors. On Rear Engine Riders, the solenoid is located under the seat or in a seprate compartment. Follow the Positive (Red) battery cable to find the solenoid.
6. No Ground. Check the ground cable at the battery and where it connects to the engine or chassis of the power equipment. Replace if necessary cable if necessary.
7. Worn Brushes. Remove the starter and remove the end cap. Do this slowly as the brushes will fly out if you are not looking for them. If you have brushes from another starter, simply replace the brushes, or replace the end cap if brushes are not available. You must use brushes from the same starter as the one you are fixing. You can't use Tecumseh brushes in a Briggs starter or in a Kohler starter.