What Does It Mean When A Lawn Mower Pops?

If you are mowing the lawn and your mower begins making a popping sound, you may initially be confused or even a little panicked. Your first thoughts likely are that it is time to replace your lawn mower. While there is a chance that these pops could be the beginning of your mower's death rattle, it is far more likely that the issue can be resolved by performing a few relatively simple maintenance tasks.

The popping sound you are hearing is often referred to as a backfire. Generally speaking, this happens when unburned gas ignites out of sync with the typical firing cycle. It can happen with automobiles or any other piece of equipment with a gas combustion engine. To that end, this is an issue for gas-powered lawn mowers, as electric mowers utilize an electric motor with no burning fuel.

While the general principle behind a backfiring engine is consistent, the specific cause can vary. Pops or backfires may be the result of issues with the air filter, spark plug, carburetor, fuel, or overheating. When a backfire occurs during the mowing process, it can help you pinpoint what specifically is happening. Luckily, whether it happens while starting, during use, or upon shutdown, there is almost always an easy fix. In many instances, the tasks required to correct the backfire are basic maintenance procedures which help extend the life of your mower. So, you can essentially kill two birds with one stone.

Often, a mower is running fine when you've prepared for winter storage, only for it to reemerge in the spring running rough and backfiring. In this instance, the culprit is typically bad fuel. The gas may have become contaminated during storage or may have simply gone bad. In fact, all gas can become stale through evaporation. Ethanol fuels have the added issue of phase separation, where water separates out and settles to the bottom of the tank. In either instance, the best thing to do is safely drain the old gas from your mower and replace it with fresh fuel.

Should your mower backfire upon first starting and have difficulty kicking in, the issue is likely your spark plug. If this is the case, remove the spark plug and either clean or replace it. Conversely, if the engine backfires when you are shutting it down, overheating is the problem. Allow the engine to idle for a minute or two during each use in order to cool it down properly before shut down. 

If your lawn mower is backfiring during use, there are a few possible causes. One is the aforementioned bad fuel issue. However, if your fuel is good, then the reason is likely either your air filter or carburetor. Your first step in this case is to remove and clean the air filter, something that should be done regularly. A clean air filter ensures your engine is receiving adequate air flow to efficiently and completely burn the gas in the combustion chamber. If that does not solve the problem, clean or adjust your carburetor as needed. This task may be best performed by a professional, unless you are adept at small engine repair.