If you have a test light and a helper, have them depress the clutch, and turn the key (make sure the blades are off mower is in neutral) FInd the starter silonoid (the red wire from the battery leads to it. put the test light on the small wire lead on the silonoid.( there will be 2 large wires and one or two small wires. if there are 2, one if the small wire just leads to ground never mind that one.) If it lights up when the key is turned but the motor doesn't turn over you need a silonoid. If it does't light up, its a fuse or a switch issue. Maybe not depressing a safety switch all the way or something simple. Good luck. ( its usually a silonoid) 14 - 20 bucks at any dealer