What are the reasons why a pull-start gasoline engine won't start?
3 Answers
Hand-pull gasoline engine is difficult to start because: There is air in the carburetor, preventing gasoline from entering the cylinder: There is an oil drain screw at the bottom of the carburetor. First, drain some oil to let it flow out. If no oil comes out, check if the fuel switch is not open or if the carburetor is clogged. No electricity in the spark plug: The spark plug is an important component of the gasoline engine's ignition system. It introduces high-voltage electricity into the combustion chamber and causes it to jump across the electrode gap to produce a spark, thereby igniting the combustible mixture in the cylinder. It mainly consists of a terminal nut, insulator, terminal stud, center electrode, side electrode, and shell, with the side electrode welded to the shell. No electricity in the spark plug will cause the engine to fail to start.
I've repaired many pull-start gasoline engines and found that hard starting usually has various causes. Check the fuel system: ensure the gasoline is sufficient and fresh, as old or contaminated fuel can clog the fuel line and affect supply. Ignition issues are also common; a worn or fouled spark plug may prevent firing, and a faulty ignition coil can disrupt the process. Air supply is critical—a dirty air filter restricts intake, leading to an insufficient air-fuel mixture. Proper technique matters; incorrect rope-pulling, like slow or inconsistent pulls, makes starting difficult. Mechanical factors can't be ignored—worn piston rings or low compression reduce efficiency. Try fresh fuel and a clean air filter first; if that fails, disassemble for inspection. Environmental factors like cold weather increase difficulty—preheating before starting helps.
Last time my lawn mower wouldn't start, pulling the rope hard didn't help. Most likely a fuel issue: either the tank was empty or the gas had deteriorated from sitting too long, clogging the lines. Next, the spark plug might need cleaning or replacing—if it doesn't spark, starting becomes difficult. A clogged air filter restricting airflow is another common cause. If the rope feels too light when pulling, there could be an internal mechanical issue like a broken recoil spring. Additionally, low oil levels increase engine friction, making it harder to start. Quick fixes: try adding fresh fuel, clean the air filter if dirty, and give it a few more pulls. On cold days, warming it up indoors first can help. Machines left unused for long periods are more prone to problems, so I make it a habit to service mine every season to prevent issues.
