One of the biggest killers of small engines without a doubt is dirt and grit that makes its way into the inner part of the engine. It’s a one-way ticket to the scrap yard. And you’re left to pick up the pieces (quite literally, as you’ll need a new engine). And that’s exactly why air filters exist. Their job is to stop this dirt and grime in its tracks. You’ve probably heard about the importance of maintaining these filters, but how exactly do you tell when they need cleaning or changing? Your mower isn’t going to start talking to you or send an SMS when it’s time, but there are some dirty lawn mower air filter symptoms that you can watch out for that will tell you when you need to take action.
The most common dirty lawn mower air filter symptoms include a sputtering engine/loss of power, a mower that won’t start up, increased fuel consumption and black smoke being blown out of the exhaust.
Common Symptoms of a Dirty Lawn Mower Air Filter
There are four common signs to watch out for when it comes to dirty or clogged air filters. And they’re all very easy to spot.
The Engine Runs Rough/Loss of Power
You’re probably very used to the sound produced by your mower’s engine (when in good condition, it should purr when in use), so watch out for any changes in that noise. Has the engine started to sputter and run rougher than normal? Is your lawn mower losing power when cutting? This could very well be a symptom of a dirty air filter.
You see, when the air filter is clogged up with dirt and dust, the air that is needed for the engine to run is no longer being supplied in the correct amounts. The sputtering sound you’re hearing is the equivalent of your mower gasping for air.
Mower Won’t Start at All
If your mower’s air filter is coated in a thick layer of dirt, it’s possible that it might not start up at all. The amount of air passing through the filter might not be sufficient to initiate the combustion process in the engine.
So if you can’t start your mower up, one of the first places to look is the air filter. Particularly if it’s been quite a while since you last cleaned or replaced it.
More Gas Being Used
A mower that has all of its key components properly maintained – including the air filter – is one that will run very efficiently in terms of fuel consumption. So if you notice that over the past few weeks, your mower is using more and more gas to mow the same amount of lawn, it could be a symptom of a dirty air filter.
As the engine is working under extra pressure (not enough air due to the dirty filter), more gas will be used. This won’t be something you notice right away, but rather something you will see happen gradually.
Black Smoke Emitted from the Exhaust
The carburetor is responsible for supplying your mower’s engine with the right ratio of gas to air. If the percentage of gas is far higher than that of air (which is what will happen when an air filter is clogged), it’s possible that you might see black smoke blowing out of the exhaust. The first time you see this, it may well freak you out, but it’s often just a case of replacing or cleaning the filter.
Watch Out for Dripping Oil Too
If you’ve been doing some repair work on your mower and had to turn it over, if you turned it over the wrong way, it’s possible the lawn mower filter is soaked in oil. If this happens, your mower will most likely be impossible to start.
So if you see any oil dripping from the air filter casing, it’s a sure sign that you messed up. The air filter should always be facing upward when you turn your lawn mower over.
How to Know You’ve Got a Dirty Air Filter: A Summary
Just like we need air to function properly (holding your breath while mowing wouldn’t be fun, or advisable for that matter), a mower will show some very obvious signs when its air supply is restricted or cut-off altogether.
- Sputtering and loss of power
- Won’t start up at all
- Black smoke coming from the exhaust
- Using too much gas
- Lawn mower is surging
If you spot any of these dirty lawn mower air filter symptoms, you need to remedy this issue right away. Continuing to use a dirty filter is not going to do your engine any good and may cause long-term damage.
If you’re tempted to run your lawn mower without the air filter, please don’t. You’ll thank me later!
Found clogged air filter, high gas consumption but no black smoke. I replaced the filter, plug, coil 4.5k. Still won’t start. Is it toast??
Hi Ivan!
Seems to me that since you’ve already checked the air supply and spark, you’ve got a fuel delivery problem. If your lawn mower has been sitting for a while I would guess that your carburetor has been gummed up. Another reason to suspect this would be if your air filter was clogged with oil. If oil made its way into your air filter it could’ve gotten into your carb as well.
Cleaning or replacing your carburetor would be a good next step if you can determine that fuel isn’t reaching the cylinder. One other related problem would be fuel that has gone bad. This might also be the case if your mower has been sitting for a while.
If you get new gas and find that the fuel delivery system is working well, you might need to start looking into larger engine issues.
There’s always hope, until there isn’t. Good luck 🙂
My lawn mowers definitely blow blue smoke but only once in a while when I’m mowing. I’ll turn the throttle down and then it quits smoking, throttle up and continue mowing WEIRD…
Hi Norman,
Blue or white smoke is usually caused by the engine burning off oil. This could be due to overfilling the mower with oil, using the wrong type of oil, and even mowing steep hills/slopes.
It is commonly caused when a lawn mower has been tipped on its side to remove blades and oil has spilled into the cylinder head. I would recommend that you keep an eye on the oil level in the mower and make sure that it does not get too low.
Good luck finding the cause.
Cheers, Tom.