4 Fixes For a Lawnmower that won’t Stay Running

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In this blog post, I will discuss with you four different fixes for your lawnmower that dies soon after it starts or does not stay running for long enough for you to completely mow all the grass in your lawn.

The most common reasons for a lawnmower that won’t stay running are problems with the:

  • Air filter
  • spark plug
  • Fuel system
  • Carburetor
4 Fixes For a Lawnmower that won’t Stay Running 1

We will discuss each of these reasons in more detail on how to solve them. Each of these four guides will help you save a fairly huge amount of money, as you can fix these basic issues yourself.

Why lawnmowers won’t stay running?

Mostly, a clogged and dirty air filter will cause your lawnmower to suddenly stop running. If you want to continue using your lawnmower when its air filter is clogged and dirty, it will ultimately damage your lawnmower’s engine. The engine will get limited air for cooling and ventilation so it will run poorly, and gradually, the engine of your lawnmower will fail.

The most common symptom of a clogged, dirty air filter is a constant loss of power. Your lawnmower will refuse to run on wet or high grass. You will notice that you were previously able to mow the entire grass in your lawn two full times prior to its tank running out of gas.

But now you are unable to complete your second mowing as your lawnmower won’t stay running. It means your lawnmower’s fuel consumption rate has increased because of the clogged and dirty air filter. The result will be a coughing and sputtering engine that cannot draw in enough fresh air and will not turn over when you pull the cord or turn its key.

1.  Maintenance of the air filter of lawnmower:

There are different types of air filters available online and in stores, the foam filters need oil, while the paper and the hybrid filters, both have foam as their pre-filter and paper as their main filter. Now I will share with you a step by step guide on how to clean, replace, discard or maintain the air filter of your lawnmower. Tools that you will need include an adjustable wrench, four in one screwdriver, needle nose pliers, a pair of rubber gloves, rags and a socket or ratchet set.

You must read the user’s manual to locate your air filter. In most models of lawnmowers, it is located on the side of its engine behind a metal or plastic cover. Depending on your lawnmower’s make and model, you must use either a wrench or a screwdriver to loosen its bolts and screws that hold its cover in the proper place.

First of all, you must turn off the engine of your lawnmower, and wait for a while for all of its parts to completely stop moving. Now, you must disconnect the wire of its spark plug. Now, remove the cover and pull the old air filter out.

To clean your air filter housing, you must use a dry cloth. Never use any detergents or solvents, as they are harmful. Never clean the housing of your air filter with compressed air as it will force the dust and dirt down the throat of the carburetor of your lawnmower.

You must now carefully examine its frame to detect any cracks. You must also check its paper pleats for any holes or tears. If you find any cracks, holes or tears, you must at once discard the air filter because it cannot be cleaned now. You can gently tap a paper filter to dust off any debris inside it. A shop vacuum can also be used to clean a paper filter.

If you have a foam filter, you can easily wash it in warm water using a gentle detergent. It can be air-dried later on. It is always much better to replace a clogged and dirty air filter than try to clean it because the air inhibiting particles are too tiny to be removed by a vacuum.

Consult your lawnmower’s manufacturer to discover which air filter is correct for your lawnmower. Once you buy the correct air filter, you can easily snap it into its proper place by means of tabs.

To replace the air filter of your lawnmower, you must undo the clips and loosen the screws that hold your lawnmower’s protective cover over its air filter. You must examine the air filter carefully, by holding it up to a bright source of light. It is the proper time to discard the old air filter and replace it with a new one if your air filter’s paper element blocks enough light.

If you find any yellow or telltale brown stains on your foam filter, it is an indication that it cannot be cleaned anymore, instead, you will have to replace it with a new one. You must also examine the pre-filter carefully if its foam has become brittle, stained or stiff, you will have to replace it immediately.

After inserting the new air filter into the air cleaner assembly, reattach the protective cover carefully. Avoid pinching or harming the filter element. Never apply any pressure or force to push the protective cover in its proper place, if it does not reassemble easily, it means you have probably inserted your new air filter incorrectly.  

According to the engine manufacturer Briggs & Stratton, the paper or the foam filters must be replaced every twenty-five hours of operation, while the paper filters that have a foam filter pre-cleaner last for at least one hundred hours of operation. You must never use the compressed air to blow out a paper air clean as you may run the risk of perforating the paper. It only takes a single speck of dust that gets past the air filter to badly damage the engine.

Having a properly working air filter is the first line of defense for your lawnmower against the dust and dirt that is kicked up while mowing. A well-functioning air filter will prevent the dust from getting into the engine through its carburetor. If the air filter of your lawnmower is broken, cracked or dirty, dust will make its way straight into the engine.

2.  Maintenance of the spark plug of your lawnmower:

I will assume that you have cleaned or replaced the air filter of your lawnmower. Now the next step is to check the spark plug. The spark plug of your lawnmower is little more than a small, contained fire, that is harnessed to turn its driveshaft.

To light a fire you need a spark and the part of your lawnmower that makes the spark is its spark plug. If your lawn mower won’t stay running it could be an indication that its spark plug is worn out.  You must replace the spark plug every season or after one hundred hours of use.

If you are troubleshooting why your lawn mower won’t stay running, the following three-step guide will provide you with the resources that are needed to keep your lawnmower running right. You must make sure that the electrodes of your spark plug are always sharp and tidy to be able to produce the strongest spark needed for ignition. The more old or greasy your spark plug is the more voltage and greater tug on its rewind needed to make a powerful spark.

If you have not tuned the engine of your lawnmower recently, you will have to tug many times to turn the engine on. Your damaged spark plug is the culprit that is responsible for deposits on the cylinder, excessive fuel consumption, and oil dilution. Fortunately, the spark plug is one of the simplest and one of the most inexpensive engine parts to repair or replace.

First of all, you will have to locate and disconnect the lead of the spark plug of your lawnmower. In most models, you will find it on the side of the engine, facing sideways. It is not visible as it is hidden under a protective rubber cap, this cap is connected to the wire of the spark plug.

You will notice that this protective rubber cap creates a ninety-degree angle to help keep the wire attached near the engine. You must hold the rubber cap and pull it straight out. This is how you can release the cap and wire.

You will need a deep socket connected to a ratchet wrench or a simple wrench to remove the spark plug. You must turn the wrench anti-clockwise, carefully. Never apply too much pressure or force or the spark plug will break off.

You must now inspect the spark plug to look for any signs of cracks, damage or wear. You must immediately replace the spark plug if you find heavy carbon buildup at the electrode or a broken or burned away electrode. Or if you find the porcelain insulator cracked, you must replace the spark plug.

To change the spark plug of your lawnmower:

  1. Find the right spark plug and adjust its gap settings.
  2. Disconnect the plug lead then remove it from a spark plug socket.
  3. Replace with the new plug, taking care, not to over-tighten then re-attach the lead of the spark plug.

Four major problems that your lawnmower can suffer with include a dirty, disconnected, defective or loose spark plug. Dust, debris, grease, gunk or grass can infiltrate your spark plug and limit its capability to spark. Sometimes you can clean the minor deposits instead of discarding the spark plug straight away.

To clean your spark plug safely, you must use a spray-on plug cleaner and a wire brush that is specially produced for ignition parts. To get rid of the stubborn deposits you can make the use of a knife also. But you must never use abrasives or shot blaster to clean the spark plug.

Check the spark plug for any moisture, if it is wet, there is no way your lawnmower will stay running for long enough. A wet spark plug indicates a malfunction in the choke system of your lawnmower, an excessively rich fuel mixture or water in the fuel. A dry spark plug, on the other hand, indicates a clogged or stuck carburetor inlet needle or a leaking carburetor mounting gasket.

While you are removing your spark plug, you must pour one teaspoonful of fuel into the hole of the spark plug. You must clean your spark plug using a carburetor cleaner. Don’t attempt to clean it with compressed air alone as it is not enough, you will need detergent or solvent to get rid of oil residue, let it dry fully.

Once you have disconnected the wire of the spark plug, you can use a piece of cloth to clean the area around it, before removing the spark plug itself. This step is really helpful as it prevents the dust from entering the combustion chamber after removing the spark plug. To clean the spark plug, unscrew it and then use a wire brush and a spark plug cleaner to remove the deposits.

Your lawnmower won’t stay running if the spark plug is disconnected. The wire of the spark plug is sometimes visibly disconnected with its wire fully loose and hanging on your lawnmower’s deck. And sometimes its wire is slightly disconnected but its protective rubber cover makes it look as though it is still connected, the simple solution is to push back the wire firmly on the spark plug.

To determine whether your spark plug is defective or not, you can use a spark plug tester. You will notice a strong spark between your tester’s terminals while your lawnmower’s engine is cranking. If you don’t see any spark, it is an indication that your spark plug is defective and it must be immediately replaced.

These defects occur due to too much corrosion. If your spark plug is corroded, discard it and replace it with a new one. Never use a spark plug for more than one hundred hours of operation.

Sometimes, the spark plug itself not its wire has worked its way outward, it will lose contact with the engine. The simple solution is to tighten the spark plug clockwise using a ratchet wrench or a simple wrench.

If the fuel is more than one month old, you must dispose of it and refuel the tank with new gas. Now reinstall and reconnect the spark plug and try starting the engine of your lawnmower immediately. It can take a few pulls to fully suck the fresh gas into your lawnmower’s carburetor. If it takes too long to run properly it is recommended to clean and dry your spark plug a few more times.

3. Maintenance of the Fuel system:

If your lawn mower won’t stay running, it probably has problems with its fuel delivery system or fuel linkage system. You must make sure that the fuel system of your lawnmower is as clean as possible. The fuel that cannot reach the engine is a major reason why your lawn mower won’t stay running. 

When the fuel is consumed by the engine of your lawnmower, it’s level in the fuel tank drops. To make up for it, the fuel cap makes the use of a small vent to allow the air from outside to get into the fuel tank. If this small vent of your fuel cap is clogged, the air from the outside will not be able to get into the fuel tank, this will create a vacuum or vapor lock.

This obstructs the flow of the fuel to the carburetor causing your lawnmower to stop again and again. To find out if the vent in the fuel cap is clogged or not, you can try slightly loosening the fuel cap, then starting the engine of your lawnmower. If loosening the fuel cap lets the lawnmower to stay running, it means that it is clogged and must be immediately replaced.

If you can see any dust or dry grass on the pinhole, remove the fuel cap then clean this pinhole or vent with a shot of compressed air. To repair the fuel line of your lawnmower, begin by practicing safety: put on a pair of nitrile or latex gloves for protection against caustic gasoline, then disconnect the spark plug as given above, wait for the engine to fully cool down, then completely drain the mower’s fuel tank. Keep a small container near the mower to catch any spills.

Make sure you have clean and fresh fuel in the tank of your lawnmower. After refilling, make sure the fuel shut-off valve is clean and open. Dust and stale fuel are the most common causes of your lawnmower not running long enough.

If you store your lawnmower throughout the winter season with untreated gas in its tank, gradually it will lead to engine damage. To prevent this problem in advance, you must use a fuel stabilizer.

To fix the fuel system of your lawnmower you must remove the air cleaner. Then inspect the choke plate which is mounted on a shaft at the opening of the throat of the carburetor. The choke plate must be free of dust, must move freely and close easily.

A greasy choke plate won’t let your lawnmower stay running. Use a spray-on choke cleaner or a spray-on carburetor cleaner to clean the choke plate so it moves easily. If your lawnmower has a fuel valve on the base of its fuel tank, then you must turn it off.

Now you can remove the fuel line from the tank of your mower. You must carefully inspect the fuel line to know if it is clogged. Clean the fuel line if needed.

Now reconnect the fuel line and turn on the fuel valve. If your mower has a fuel pump you must be sure that it is working correctly. You must close the fuel supply to the pump by either turning off the valve or clamping off the fuel line.

Now you can remove the fuel pump. You must carefully inspect to see any cracks. If you see any cracks you must replace the entire unit immediately.

If your pump’s inner parts are brittle or worn out, you will have to rebuild the fuel pump using the repair kit supplied by the manufacturer of your lawnmower. The best remedy for a gas-powered lawnmower is the use of fresh fuel with an Octane rating not less than eighty-seven and alcohol rating not more than ten percent. The alcohol content in modern fuels can oxidize inside the tank and attract dampness, it can also eat away at the plastic parts such as the hoses.

The air-fuel system is also crucial to the engines powering the lawnmowers. The air-fuel system is made up of cylinders, pistons, rings, and valves. This system controls how the air and fuel move through the engine.

The pistons move back and forth pushing the air-fuel mixture to the ignition system. The piston rings keep it sealed up tightly. The intake valve lets the air in and the exhaust valve pushes the air out.

If there is no proper clearance in the valve or the valve is leaking, this will not let your lawnmower stay running for long enough. You can detect the problem in this system, using a leak down tester.

4. Maintenance of the Carburettor

The tools that you will need to clean your carburetor include a carburetor cleaner, a stiff wire and a pair of plastic gloves. The tools that you will need to rebuild and replace your carburetor include an adjustable wrench, clamps, four in one screwdriver, needle nose pliers, nut driver, organic vapor respirator and a socket or ratchet set. It is always wise to avoid last moment shopping trips by having all the tools ready ahead of time.

To take off the carb, you must turn off the fuel valve. You can now track its fuel line down to the carb to remove its hose. If your fuel line is cracked or damaged or it is leaking, you must immediately replace it.

You will see an overflow hose outside the carb, you must remove it. Now you can loosen the screws of the clamps in the back and front of your carb. Make sure the carb is fully loose to let you turn and twist it to take it off.

The carb is held in its place by a throttle cable. You can take off this throttle cable if you twist the top cap. Now you can unscrew it, as it will come off, you will see that the slide is still connected to it.

Once you have taken off your carb, you must now take off the throttle slide from its cable which is still connected to your lawnmower. After you unhook the cable, pull everything off the cable.

To clean your carb, first of all, you must take apart the float from the bottom of the carb. To take apart the float bowl, you will have to unscrew all of the four screws from the bottom of the carb. Now you can pull off the float bowl.

Be careful enough not to damage the gaskets, otherwise, you will have to replace them. Use a pair of needle-nose pliers to take off the float pin. First, remove the pin, then the float.

If your carb has splash plates, you must take them off too. The splash plates need to be taken off to get to the jets. Take out the float needle to clean it.

On the sides of your carb, you will see an air screw and an idle screw, take them off too. Take out the choke from the carb. Take off all the gaskets and O-rings.

The carb becomes clogged when you leave the fuel in your mower for a very long period of time. With the passage of time, some ingredients in the fuel can evaporate, leaving behind a sticky and thick substance. This thick, sticky substance causes your carb to clog and won’t let your lawnmower stay running.

The best way to clean the carb is to soak it in a gallon of carb cleaner, but this method is really expensive. You can use a spray-on carb cleaner instead, which is affordable and cost-effective. Before spraying, scrub the carb with a wire brush.

Carefully, spray into all the holes that the air screw, idle screw, choke, float needle and jets come from. To fully clean the jets, use compressed air. Use compressed air to blow dry all of these parts and the holes.

Install all the parts back into the carb in the opposite order in which they were taken off.

In order to conclude this blog post, I would say that if the performance of your lawnmower does not improve after following all of the four maintenance guides given above, then you must show it to a reputable professional mechanic. It is really important to maintain the health of your lawnmower as it grooms the beauty of your lawn.