If your lawn mower isn't starting, one possible reason is a bad fuel pump. Fuel pumps are responsible for moving fuel from the gas tank to the carburetor, and if they fail, your engine won't get the gas it needs to run. There are a few symptoms that can indicate a failing fuel pump:
-Your engine cranks but doesn't start. This is often due to a lack of fuel reaching the carburetor.
-Your engine starts but then dies shortly after. This can be caused by either not enough fuel reaching the engine or air getting into the fuel line.
-Your engine runs rough or stalls frequently. A bad fuel pump can cause uneven fueling, which can lead to these issues.
If you suspect your fuel pump is failing, take it to a mechanic or lawn mower repair shop for diagnosis and replacement.