If your John Deere mower won't start, let it sit a few minutes in case the engine has been flooded. Check the gas tank. Depress the primer bulb--the side of the engine should indicate how many times this needs be done. Make sure the choke is on and the "engine on" switch is engaged. Pull the rip cord in long, smooth strokes three times. If this does not work, remove the air filter and check it for dirt or rust. Replace the air filter if needed. Unscrew the spark plug from the side of the engine and inspect it for corrosion or rust deposits. Sometimes the metal contact points become bridged by metal buildup, preventing it from sparking. Use a nail file to clear out the contact points and fit the plug back into the engine. You may slso need to replace the plug. Finally, the carburetor may need to be adjusted if the mower hasn't been serviced in one or more years.
Engine Won't Start
Lawn Mower Rattles and Vibrates Excessively
If your mower rattles and vibrates, switch off the engine and lift the mower. The metal casing in which the blade of the mower spins is called the deck. The inside of the deck can become clogged with grass, which forms a thick spongy layer that can grow so large that it impedes the spinning of the cutting blade. Scrape it out and start the engine up again. Make sure the throttle is completely open, as low RPM can cause rattling as well. Press your hand down firmly atop the engine. If the rattling stops, it's because the mounting bolts holding the engine to the deck are loose. If the rattling continues, then it's likely the blade of the spindle upon which it rotates is bent, causing an imbalance. Such a problem can only be fixed in a fully equipped repair shop.
Yard Debris Is Not Discharging From Mower Normally
Turn the engine off and check the mower blade. If it is notched or dull, sharpen it. Make sure the blade is designed to function with a yard debris chute. A mulching blade is designed to leave no yard debris behind. Next look at the condition of the grass being cut. If it is wet, it will get caught within the deck of the mower and clog the chute. Only mow grass when it's dry. If none of these things fixes the problem, restart the mower and begin to the cut the grass as usual. Make sure the throttle is open so the blade spins at optimum speeds. Reduce the moving speed of the mower so it has more time to cut each patch of grass.