How to Start a Lawn Mower and Troubleshoot Common Problems
After a long winter’s rest, your mower may need a nudge before springing to life. Follow these simple steps for starting a lawn mower—and learn how to troubleshoot a mower that won’t run.
Unless you’re planning to hire a lawn care company to handle your yard maintenance, you’ll need to learn how to start a lawn mower if you want to maintain a well-kept lawn. In addition to learning the basics, it’s also crucial to understand what factors influence how easy (or how difficult) it is to start a mower, including gas and oil levels and the condition of the spark plug and mower deck. The methods below will walk you through starting a lawn mower and help you troubleshoot any problems you may encounter along the way.
Below is the gear you might need to get your lawn mower up and running. It’s more than likely, however, that you won’t need more than a few items. The equipment you use will depend on whether there’s anything wrong with the mower, and the troubleshooting tips you follow below.
SAE 30 motor oil
Spark plug socket
Replacement spark plug (consult manual for the appropriate part for your mower)
Before You Begin
Before starting up the mower, take a moment to walk your yard and clear it of any sticks, toys, and other obstacles that could damage your mower blade. Make sure that you have gas, oil, and other materials listed above close at hand.
Starting a Lawn Mower
Whether you’re new to lawn mowers, know how to use a lawn mower but have forgotten how to start one after a long off season, or are dealing with a mower that is refusing to start, these steps will help you get that mower up and running.
STEP 1: Check if your mower has gas and oil.
Look for the large black cap on the top of the mower engine (it should have an imprint of a gas tank on it). Unscrew the cap and peer inside to see if you need to add gas.
The cap for the oil pan will be on the opposite side of the engine. Look for an imprint of an oil can on the cap. Unlike the gas cap, which screws off, you should be able to remove the oil cap by giving it a half turn counterclockwise. You’ll know you have the right one when you pull the cap out and there’s a dipstick attached to it. Wipe the dipstick clean with a rag, replace it, then pull it out again and check the oil level. The oil level should be between the two marks on the stick.
STEP 2: Add gas and oil if needed.
If you’re adding gas, use the same unleaded gas you put in your car, and not the 2-stroke gas/oil mix that other yard equipment uses. Most push mowers hold between 1/4 and 2 gallons of gas. Use a funnel to avoid spilling the gas as you add it to the tank.
If you need to add oil, check the lawn mower’s user manual to see what oil weight the manufacturer suggests. If the manual does not specify an oil type, use SAE 30, the best option for engines that operate in warmer temperatures.
STEP 4: Prime the engine.
Priming the engine is necessary only if the lawn mower has not been used for a prolonged period of time (over the winter, for instance). Once you’ve attended to the mower’s gas and oil, press the primer button three to five times in order to channel gas into the engine. If you’ve used the mower recently, you can probably skip this step.
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STEP 5: Pull the starter cord.
Notice how there are two handles on the lawn mower, each running horizontally only inches apart from the other. Press and hold these handles together, keeping them together as you pull the starter cord. Do so quickly and with considerable force, and the mower engine should to turn over. Sometimes it can take several attempts before pulling the starting rope achieves the intended result: a purring motor.
Troubleshooting Lawn Mower Issues
If you’ve already checked that the mower has ample oil and gas and it still won’t get up and running, it’s time to start troubleshooting. Here are the steps you should take to determine why your lawn mower won’t start:
Check the carburetor.
If you have already confirmed that there’s oil and gas in the mower, but the engine still refuses to start, it’s possible that either the carburetor has flooded or the cylinder has become soaked with gas. (The smell of unburned gas is a telltale sign.) Leave your mower on level ground for at least 15 minutes, which should allow enough time for the gas to evaporate from within the mechanism.
Check for old gas.
If you are starting your lawn mower for the first time after a long off-season in the garage, gas that was left in the machine may have gone bad. If you suspect this is the case, observe the mower the next time you try to get it going: Does it appear to start up, then quickly stall out? The fix is simple: Siphon the old gas and replace it with fresh fuel.
Check for spark plug problems.
While the spark plug’s location can vary depending on the mower, most of the time you’ll find it at the front of the engine. Pull the rubber cap off the spark plug. If you spot debris on the end of the spark plug or inside the cap, wipe it clean with a rag.
Unscrew the spark plug using a spark plug socket and socket wrench. Clean the electrode on the end of the spark plug with a wire brush and brake cleaner. If there are a lot of deposits built up on the spark plug or if it’s cracked, you’ll need to replace it with a new one. Otherwise, screw the spark plug back in, tighten it with the socket wrench, and attempt to start the engine.
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Clean the grass clippings out of the mower deck.
Lay the lawn mower on its side so you can access its underside. Use a pry bar to dislodge any built-up clumps of grass from the mowing deck. After getting rid of the large pieces, use a garden hose to spray the deck. Give it a good scrub with a stiff bristle brush to remove stubborn debris sticking to the deck. Rinse with the hose, then turn the mower back upright and attempt to start it.
If you’ve tried these methods and your lawn mower still won’t come to life, refer to our detailed guide on what to do when your lawn mower won’t start.
While starting a lawn mower isn’t a complicated task, you can run into problems if the mower is low on gas or oil, has a bad spark plug, or if clumps of grass are clogging the mower deck and blade. The troubleshooting methods will help you learn how to turn on a lawn mower and get it back in action. In the event your best efforts to start the mower fail, there may be a larger issue with the lawn mower engine. In that case, you’ll need to seek out a lawn mower repair shop for help.
For more lawn mower advice, check out our video on the most common mowing mistakes almost everyone makes.