The part(s) or condition(s) listed below for the symptom Small engine hard to start are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.
Inspect the spark plug for signs of wear or damage. If the porcelain insulator is cracked, an electrode is burned away or damaged, or there is heavy carbon buildup at the electrode, replace the spark plug. To determine if the spark plug is defective, use a spark plug tester. You should see a strong spark between the tester’s terminals when the engine is cranking. If there is no spark, this indicates that the spark plug is defective and should be replaced.
The engine may be getting too much fuel or not enough fuel. This is usually due to the carburetor not working properly. If the carburetor is clogged, the engine won't get enough fuel. If the carburetor choke isn't closing properly, the engine may get too much fuel.
As fuel is consumed, the pressure in the gas tank rises. To relieve this pressure, the gas cap uses a small vent to allow air to enter the gas tank. If the gas cap vent is clogged, air won’t be able to enter the gas tank, and the pressure in the tank will begin to rise. When the pressure in the gas tank exceeds the pressure in the engine, the engine may be hard to start. To determine if the gas cap vent is clogged, try slightly loosening the gas cap and then starting the engine. If the loosening the gas cap allows the engine to stay running, this indicates that the gas cap vent is clogged. If the gas cap vent is clogged, replace the gas cap.