When you own a mower long enough, you will run into times when it doesn’t start. Finding the starting problem on your push mower can be frustrating. I find it more frustrating when the mower won’t start after I’ve checked everything I can think of. In the heat of the moment, it’s easy to forget a couple things. I’ve outlined the items you should check when your push mower doesn’t start.
A push mower won’t start when your mower cannot get the fuel or air it requires to start. This may be due to bad fuel, a faulty fuel pump, plugged filters, clogged fuel lines or a dirty carburetor. A bad spark plug, broken recoil, bad battery and bad switch can also cause your push mower to not start.
Keep reading and I’ll share the items to check along with how to resolve your starting problem.
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13 Reasons Your Push Mower Won’t Start
No Gas or Wrong Gas in Your Push Mower Fuel Tank
Begin with the most obvious problem: fuel. If you don’t have gas in your push mower, your gas-powered mower will not work. Most push mowers today use a 4-cycle engine that require an unleaded gasoline with an octane rating of 87 or greater and an ethanol level of 10 percent or less.
An older push mower may use a 2-cycle engine which requires an oil and fuel mixture to run your mower. Many gas caps indicate if you are to use an oil and gas mixture. You can also refer to your owner’s manual to determine what type of fuel to use in your older push mower.
Never run straight gas through a 2-cycle engine requiring an oil and fuel mix. If you do, you will most likely have to replace your engine. Using a fuel with a 10% or lower ethanol content is required for these types of engines as well.
Fix: Fill your gas tank with fresh unleaded gasoline using an 87 octane or greater. Choose a gas with an ethanol level no greater than 10%. When your push mower uses a 2-cycle engine, you will want to mix fuel with an oil designed for 2-cycle engines at the mix ratio recommended by the manufacturer.
Find more information on the correct fuel for your 4-cycle gas lawn mower here.
Bad or Old Fuel in Your Push Mower
Gasoline begins to break down and lose its effectiveness after 30 days. Ethanol in your fuel will begin to separate from the gasoline and sink to the bottom of the fuel tank along with the moisture it attracts. The ethanol and moisture combination, once it evaporates, leaves a gummy residue that can cause clogging in the fuel system. Clogging prevents fuel from getting to the engine which will keep your mower from starting.
Because fuel begins to degrade relatively quick, it is best to purchase your fuel from a busy gas station and consume it within 30 days. If you have more than a 30-day supply on hand, you need to stabilize it with a fuel additive like Sea Foam Motor Treatment. I explain more about the advantages of using Sea Foam in this article and why this is the fuel additive I use.
Fix: Remove the old fuel in your push mower, flush the tank and add fresh fuel.
Faulty Push Mower’s Fuel Cap
Fuel caps have a vent to allow air to pass through the cap. If the vent on your push mower’s cap is plugged, your gas tank forms a vacuum that prevents your mower from allowing gas to leave the tank.
Fix: Replace your push mower’s gas cap if you are unable to clean the cap and open the vent.
Push Mower Has a Bad Spark Plug or Loose Connection
When your spark plug has a loose connection or it is not properly gapped, your push mower’s engine can misfire or fail to start. A plug that is very dirty with carbon buildup or oil can foul out causing starting problems.
Fix: Remove your spark plug and inspect it for signs of carbon buildup or cracked porcelain insulator. Replace with a new spark plug if you find it is damaged or unable to be sufficiently cleaned. Check the connections on your spark plug and make sure it is gapped according to the manufacturer’s specification.
Push Mower Air Filter is Plugged
A push mower uses a thin, rectangular shaped, air filter. It will typically be a paper or foam air filter. The function of your air filter is to prevent dirt and debris from entering the air intake and damaging your engine.
Your mower needs air to run. When the source of air is blocked, your engine is starved of air and will not start. Running plugged air filter not only can cause your mower not to start and run, it may also cause extensive internal engine damage. This could mean having to purchase a new push mower.
Fix: Take time to inspect your air filter regularly. Clean and replace when necessary. To access your air filter, unscrew the thumbscrews to remove the cover on your air filter housing. Remove your filter. Be careful to not knock dirt into the air intake when you remove your filter. Wipe out any dirt with a clean dry cloth.
Clean a Push Mower Paper Air Filter
Tap your paper air filter against a solid surface to knock as much dirt out of the air filter as you can remove. Hold your paper filter up to a light source and look to see if you can see light shine through the element. Reuse a filter where you can see light. If you can’t see any light, you need to buy a new filter.
Clean a Push Mower Foam Filter
Wash your foam filter with water and a mild dish soap to remove dirt and oil. Rinse with water until the soap is removed and lay flat to dry. Placing the filter outdoors in the sun will speed up the drying process. Once dry, lightly coat with a filter oil and reinstall. If you find your foam filter is brittle, has brown spots or has been torn, it’s time to replace it with a new filter.
Bad Push Mower Fuel Pump
Your push mower may or may not use a fuel pump. Your mower will use a fuel pump when the carburetor sits higher than the fuel tank. It requires a pump to push fuel upward to the carburetor to work against gravity.
A fuel pump can wear out over time and fail to work. Most vacuum fuel pumps are made of plastic which can degrade from the effects of fuel. Your push mower will not start if your pump no longer can hold pressure and push fuel to the carburetor.
Fix: You need to troubleshoot your fuel pump to determine if this part is the cause of your push mower’s starting problem. Fuel leaking from your pump is a good indication your pump is bad.
If the fuel pump isn’t leaking, you will need to perform some additional steps to identify a failing fuel pump. Use your fuel shut-off valve or hose clamps to start and stop flow to test flow. First check, for fuel flow to the inlet port of the fuel pump to verify fuel is getting to the pump.
Once you verify the fuel supply to the pump is not the problem, check for flow out of the fuel pump. Disconnect the fuel hose off of the carburetor and place it into a container. Start your mower and watch for a consistent or pulsating flow of fuel out of the fuel line. If you don’t have good flow, you must replace your fuel pump.
Plugged Fuel Filter on Your Push Mower
Most push mowers don’t use a fuel filter, but if yours does, you’ll want to check it to make sure it is not plugged preventing fuel from continuing to flow through your fuel system.
Fix: Replace a dirty fuel filter. Make sure the filter is installed correctly. There is an arrow on the fuel filter to show the direction fuel is to flow through the filter.
Push Mower Has a Blocked Fuel Line
Old fuel and dirt leave deposits that can clog your push mower’s fuel line.
Fix: Remove the clogged fuel line, spray carb cleaner into the tube and use canned air to blow air through the tube until the line is free of dirt and gummy residue. Replace the fuel line when you notice the line is dry and forming cracks.
Clogged & Dirty Carburetor on Your Push Mower
The function of the carburetor is to regulate the right amount of gas with the right amount of air so your engine can create a combustion. Carburetors can get crusty buildup and gummy deposits from using old fuel containing ethanol. When the carburetor is not able to regulate fuel in your push mower, your engine will run rough or it may not even start at all.
Fix: If you are somewhat mechanical, you can try to clean the carburetor yourself, otherwise bring it to your lawn mower repair shop. You can find steps for cleaning your carburetor in this article.
Bad Ignition Coil
The ignition coil sparks the spark plug to start the engine. When the coil is bad, your push mower won’t start.
Fix: After you have check your spark plug is working, check the continuity of your ignition coil using a multimeter. Replace the ignition coil if you find a break in the continuity. You don’t need an expensive multimeter. This one will work to identify your electrical problems on your push mower.
Bad Battery or Charger on Your Electric Start Push Mower
If you have an electric start mower, you will have a small battery in your push mower that provides power to the electric starter. Charge your battery using a charger plugged into the outlet on your well. Some batteries must be removed to be charged, while others have an outlet that plugs into the wall.
Fix: Replace your battery and/or charger when you battery won’t charge or it fails to hold a charge.
Blown Fuse on Your Push Mower
Check the fuse on your push mower. The fuse is used to protect your electrical system.
Fix: When the fuse is blown, replace the fuse with the same amperage. If you continue to blow a fuse, have your local mower repair shop troubleshoot the root cause of the problem.
Recoil is Bad on a Manual Start Push Mower
A mower with a pull-start type of push mower may not start when the recoil is broke.
Fix: A broke recoil may be resolved by restringing the recoil. It may have broken clips, pulley or spring that need to be replaced. Sometimes, it’s most cost effective to replace the whole recoil assembly than trying to repair.
Bad Safety Switch on Your Push Mower
Your lawn mower uses a safety switches in its operator’s presence control system. The switch is designed to kill the engine when the operator lets go of the safety bar on the push mower. A faulty switch may not sense the operator is present and fail to start.
Fix: You can temporarily bypass the safety switch to identify a bad switch. Do not operate a mower without the safety switch installed for your safety. Replace a bad switch.