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How to Start a Lawnmower that Has Been Sitting?

Winter has just passed with your mower sitting in the shed or garage, and now you want to mow again. But if your mower doesn’t seem to run corectly after you try to use it, or it does not start at all after getting it out from storage, don’t worry too much. Your mower is alright and needs a little maintenance routine. It’s possible to face some trouble starting a mower that has been sitting for some months because static components can jam, gas in the tank can go bad, or maybe your mower already had some problems before you stored it. It is best practice to service and clean all kinds of machines after a certain period of usage or storage, and your lawnmower is no exception. Even if the mower is not showing any signs of trouble, we advise you to perform a cleaning and servicing routine to ensure that it will not run into problems during the mowing season. This article will be your guide on how to do that.

How to Start a Lawnmower that Has Been Sitting:

  • The gas tank must be empty before you store the mower. Gas can go bad over time and cause several problems for the mower. If there is some gas sitting in the mower fuel tank, drain it and remove any varnish buildup. Always use fresh gas and never let it sit in the tank for over a month.
  • Remove the spark plug and check if it is dirty. Any buildup around the electrode area should be removed using sandpaper or a file. The best practice is to replace the old spark plug with a new one once a year.
  • If possible, clean the air filter. If the filter is too dirty to be cleaned, it should be replaced with a new one.
  • Over a long period of use, the carburetor becomes dirty, clogged, or corroded. Problems with the carburetor can prevent your engine from starting or running smoothly. So, check the carburetor and clean it if possible. If the carburetor is faulty beyond repair, replace it with a new one.
  • Check the oil before even trying to start the mower. Oil should be of good quality and enough amount. We advise you to change the oil twice a year for your mower’s best health, but at least one oil change a year is necessary.
  • The brake cable should be adequately tense before you start using it. Tighten the cable if it is loose.
  • Too much oil in the engine can enter the fuel pump and make it faulty. So, check the fuel pump on your mower that has been sitting and make sure it’s working fine.
  • Check to see if the flywheel is broken. Before you start a mower sitting, make sure that the flywheel is intact and working alright.

Following this easy to do routine will do great good for your mower. Before starting a sitting mower, these simple things will ensure that it starts normal and runs smoothly throughout the mowing season. More details to help you through each of the fixes mentioned above are given below.


Safety comes first. Before working on your mower, make sure that it is parked on an open level area. Wear safety gloves and goggles. Stay aware of sharp blades and sharp engine parts and edges. Keep a first aid kit nearby.


One of the most important things to do before starting a sitting mower for some months is to check its oil. Although the best time to change the oil is about half an hour after you have finished mowing, checking the oil before starting a sitting mower and changing if necessary is advised too.

Always use good quality oil and one with the right grade for your lawnmower. Furthermore, the oil should be clean and free from any residue. Also, make sure that there is enough oil for the mower to keep working smoothly. A smoking mower could indicate an oil leak. In case of a smoking mower, consult the user manual or take help from a professional mechanic.

If the oil is dirty or very black, it can become a contributing factor to your mower’s problems. So, change the dirty oil before starting a sitting mower. Changing oil is not difficult, especially for smaller mowers, and you can do it yourself. Changing the oil on a walk-behind push mower will take 15 minutes of your time tops.

Changing the mower’s oil at least once a year is a must. The best practice would be to change the oil twice a year- once at the start of the mowing season and once before winterizing the mower.

The old oil should be properly disposed of. You can take it to the nearest mechanic shop in a sealed container or use your city’s disposal program.

● Gas:

Obviously, your mower won’t start on an empty tank. Put fresh gas in the tank before starting the mower.

If there was gas already sitting in the tank, you need to drain it or siphon it out. Gas goes bad after some time, and using old bad gas can cause numerous engine problems.

After taking out the old gas, put fresh gas in it. It is advised to add a fuel stabilizer to the gas in the correct ratio. A fuel stabilizer will keep the gas stable for a longer time. Consult the user manual or a local mechanic for more info about the use of fuel stabilizers.

If you had to take out old gas, make sure to dispose of it properly according to municipal guidelines.

● Air Filter:

A mower with a faulty air filter will stop while running because oxygen is required to combust fuel, and a faulty one decreases or block the supply of clean air.

Check the air filter for dirt and clogging. If it is not too dirty or clogged up, you can clean it using a brush, soap, and water and install it back. If it has gone to bad and cleaning it is impossible, replace it with a new one. A clean new filter will ensure proper air supply for fuel consumption, and your mower will start and run smoothly.

Air filters are not too expensive. You can find the right-sized filter for your mower in a parts stores near you for around 10 bucks.

● Spark Plug:

Locate your mower’s spark plug. It is covered with a black rubber wire. Take the plug out using a wrench and check for corrosion or black buildup of carbon around the electrodes.

If it is not too dirty, a spark plug can be cleaned using sandpaper or a file. If the plug is too dirty to be cleaned, replace it with a new one. Make sure that the new spark plug matches the size and specifications of the old one. Also, make sure that the plug’s connection wire is not broken or damaged.

Another important thing to remember as far as the spark plug is concerned is to disconnect it before performing a repair or servicing of your mower. You can disconnect the spark plug simply by disconnecting the rubber wire connected to it.

A faulty spark plug prevents your engine from starting or cause it to die out during operation.

● Brake Cable:

A mower with a loose brake cable will be difficult to stop and may cause accidents. Before starting a mower that has been sitting, make sure that its brake cable is tight.

Testing the brake cable is very easy. Just pull the brake handle and then pull the cable with your hand to see if it is properly tense or not.

● Carburetor:

If your mower doesn’t start right or run smoothly after the storage period, the chances are that it has a faulty carburetor. After you have checked the things mentioned above, test the carburetor too.

After using the lawnmower for a long period, its carburetor becomes corroded. If fuel is left in the mower during storage, it can evaporate, producing a sticky varnish-like substance that clogs the carburetor. If any of these things happen, the carburetor is faulty and needs some work.

If the carburetor is not too dirty, you can clean it with carburetor cleaner or vinegar. But if it is too dirty, you must replace it with a new one.

Carburetors of small engines are easy to find in local mechanic shops or online and don’t cost much.

● Fuel Pump:

The fuel pump pumps fuel to the engine via a series of three ports. A fuel pump can become faulty if there is too much oil in the engine and some of it leaks and enters the fuel pump.

Checking the fuel pump involves checking the pulse ports line, diaphragm, and valves inside the pump. If you have already done the servicing processes discussed above, but your mower still has issues, it could be because of a faulty fuel pump.

Unfortunately, the fuel pump cannot be repaired once defective. A faulty fuel pump has to be replaced with a new one.

● Flywheel:

A flywheel is a horizontal wheel inside the mower that starts when the starter cord is pulled. Flywheel plays a role in starting the engine.

If your mower runs over a rock or hits an obstacle, its flywheel can break. Before starting your sitting mower, check the flywheel, and if it is broken, get it replaced.

Final Remarks:

It is not uncommon for machines to show signs of trouble when they are started after sitting for a long time. If your mower has been sitting in storage for some months and is now not running smoothly, there is no need to lose hope. You can recover its normal working by performing the servicing routine mentioned above. Most of the things mentioned above should be done before even starting a sitting mower for the first time. Proper maintenance of machines makes their operation better and extends their lives.