If your lawn mower doesn't fire up, it might not just be an empty gas tank. There are many different factors that cause this complex machine not to start. Before you replace your mower or spend lots of money
Siphon the Tank
Sometimes, you just need a full tank of fuel to get a gas-powered mower working again. However, if the tank is already full, the gasoline might have gone bad from sitting idle for over a month. Use a siphoning device to pump out the bad gas and refill the tank with fresh gas. Make sure to prime the mower before starting.
Check the Spark Plug
See if the spark plug has burned out, and if so, swap it out with a new one. If it's not burned out, the spark plug could be out of place or may not be receiving enough gasoline due to buildup. Detach the ends of the gas line and clean them out to make sure gas is getting through.
Examine the Air Filter
Remove the lawn mower's air filter to see if it should be replaced. If it hasn't been changed in a while, the filter could have a high buildup of debris that's not allowing proper airflow to the engine. Try starting the engine without the dirty air filter, and if the machine fires up, replace it with a clean one.
Look at the Oil Level
Verify that the oil level is correct. If it's too low, then add new lawn mower oil to your machine. You should also change the oil if you notice it's very thick or darker than usual.
Follow the Correct Starting Controls
Make sure that the starting controls are properly set when starting it. Take a moment to check the lawn mower owner's manual to verify that you're not forgetting a step. Some common missteps include not setting the choke correctly or not keeping the machine on level ground before starting.