Image of a lawn mower but Why Lawn Mower Starts then Dies?

Why Lawn Mower Starts then Dies? Guide to DIY Lawn Mower Fixing

A lawn mower is a great addition to your home and garden resources as it help spice up your yard and the surrounding. These units feature powerful engines designed to power the mower over huge patches of grass and hilly terrain. They also incorporate sharp blades to enhance a well-manicured look, strong wheels for stability, and other solid features that ensure you keep going. However, frustration sets in when your mower starts misbehaving like powering on and off, you would be wondering why lawn mower starts then dies

A lawn mower that ignites well only to die a few seconds later likely has fuel system issues. Fuel runs from the gas tank through the carburetor to the cylinder. So your mower engine could have fuel flow restrictions anywhere along this line.

Other issues can also cause your mower to die a few minutes after ignition. So keep reading as we unfold more about this in the article. Here’s I will look at some of the reason a lawn mower would fail and possibly how to handle such shortcomings without having to call a specialist.

Why Does My Lawn Mower Only Run For a Few Seconds Then Dies? 

Similar to other equipment, a lawn mower can encounter problems before nearing the end of its better days. These problems occur due to the high demands of mowing your lawn. So in this guide, we will touch on different problems that allows your mower fire up well, run briefly, then die after a few seconds.

The most likely problems with your mower could be:

  • Dirty Carburetor

A dirty carburetor could be the main reason your mower engine ignites, run for a few seconds, then dies. 

A dirty mower carburetor affects proper mix of fuel and air. As such, the explosions created by the combustion engine become too weak to sustain the mower to run.

So if your mower have a dirty carburetor, clean it thoroughly to get your mower running. If any interior components are damaged, replace the carburetor and test the mower. 

  • Low Oil

Running a mower with insufficient oil can keep it from starting because the engine is not adequately lubricated. This is very dangerous as the engine’s internal components can damage, resulting in costly repairs.

So before starting the mower, check the oil level as some mowers integrate a low oil level switch to disable starting. 

  • Faulty Spark Plug

A spark plug offers a source of ignition for your lawn mower. So if it’s damaged or dirty, your mower will start to die only a few seconds later. So if that’s your problem, remove the spark plug, assess its appearance and determine if it needs replacement or not.

Check the center electrode to ensure it has a flat top. If the top is not flat, you need to replace the spark plug for your mower to resume operation.

You will also want to check out cracks or chips in the porcelain sheath and the firing electrode.

If you don’t notice any faults, but the plug appears black with carbon deposits, clean it using a wire brush and adjust the gap between the electrodes.

How Do You Unclog a Lawn Mower Carburetor? 

A lawn mower carburetor plays a vital role as it facilitates the mixing of fuel and air in an exact ratio to maximize power and reduce fuel consumption.

Ideally, it regulates the balance of fuel and air based on the type of terrain you’re mowing, how long the engine is running, and more.

However, this device gets covered in small lawn debris over time due to regular use. This debris buildup disrupts the carburetor’s role within your mower’s internal combustion engine.

So you need to check it regularly to ensure it’s in good working order. Without frequent checkups, you may incur additional costs in replacing the carburetor. 

Before we dig deep into the steps of unclogging your mower carburetor, let’s first diagnose the symptoms of a dirty carburetor. 

  • The mower has a difficult start. 
  • The engine usually starts but stalls while you are mowing.
  • You will notice black fumes coming out of the muffler. 
  • You will notice an increase in fuel consumption. 
  • The engine runs rough when mowing. 

Now that you have diagnosed the signs of a dirty carburetor, it’s now time to clean it using the steps given below: 

Step 1: Prepare Your Mower 

First, position your mower on a flat surface, then switch off the engine and wait for it to cool. If necessary, remove the engine cover, then use a screwdriver to unfasten the bolts securing the air filter in place.

After that, uninstall the air filter housing and check the air filters to ensure they are free from dirt. If they are dirty, clean them thoroughly or replace them. 

Step 2: Disengage Fuel Pump from the Carburetor

Now that the carburetor is exposed, access the fuel valve to shut it off or pinch the fuel line and disengage it from the carburetor. Doing this will spill some fuel, so be prepared to wipe out any spillage.

After that, disengage the choke and throttle linkages from the throttle lever, then unfasten the mounting bolts holding the carburetor. 

Next, unthread the screw holding the carburetor bowl and remove the float pin to release the needle. 

Step 3: Clean the Carburetor

After exposing the carburetor’s intake and outlet ports, take your dedicated carburetor cleaner and spray it into the ports to clean all residue. Don’t disregard any part, including the bowl. 

After that, remove the pilot jet and spray the carburetor cleaner through it. 

Reminder: If your carburetor has any signs of rust, use medium-grit sandpaper to scrub out the rust. 

Step 4:  Reassemble the Carburetor

After scrubbing off rust buildup, let the carburetor dry for some time, then reassemble it, ensuring all hardware fits in their exact position.

After mounting the rebuilt carburetor, connect the throttle linkages to the throttle lever, engage the fuel line to the carburetor, and screw in the air filter housing. Next, Install a new air filter correctly, and that’s all. 

What Can I Use Instead Of a Carburetor Cleaner? 

You can use a brake cleaner to spray the inside components of your carburetor. A brake cleaner has similar working principles with a carburetor cleaner and will dissolve all grime buildup in no time. 

If you choose to go DIY then Mix 1-quart alcohol with 1-quart acetone, and 1-quart Xylol in a 1-gallon of paint thinner can to make carburetor cleaner that works pretty well. It will dissolve the gum and all the heavy varnish that has built up inside and outside your lawn mower’s carburetor.

Why Does My Lawn Mower Sound Like It’s Dying? 

When your mower surges, it howls as if the engine reaches maximum speed, only to decelerate shortly. The engine won’t die, but this issue may repeat throughout while mowing.

Mowers depend on sufficient amounts of gasoline and air for smooth functioning. So if these two go beyond or below average measures, your mower might sound like it’s dying.


Whenever your sounds like it’s dying, watch out for the following aspects:

  • Check the Air Filter

The first culprit when fixing a surging mower is the air filter. You need to check it to see if it’s dirty because a clogged air filter denies the engine cool air for the mower to run smoothly.

If your mower has foam filters, remove them and wash them with water and a liquid detergent. If it uses a paper filter, dispose of it and replace them with new ones. 

  • Fuel System 

Your mower’s gas tank has a cap vented with a small hole. This hole is large enough to let air into the tank, creating immense back pressure to help in fuel delivery to the carb.

But given that the hole is too small, it can clog up with dust buildup or dirt while mowing. As such, it causes your mower to sound like it’s dying. So you need to clean the vent for your mower to run as expected. 

Tip: Avoid leaving your mower out in heavy rains as the water that gets into the fuel can cause surging. If water enters your fuel tank, empty the tank, dispose of the existing fuel properly, and add a fresh gasoline batch. 

  • Carburetor Issues

A gummed-up or contaminated carburetor can surge your mower engine. If you’re well-versed with handling carburetors, unfasten the bowl and clean your carburetor.

Examine the float and test to see if it moves up and down freely, then clean all tiny ports on the hold-down bolt. Apply carburetor or brake cleaner to the needle valves and jets to peel down stubborn dirt. 


If you notice serious problems such as broken jets, damaged gaskets, or internal parts, replace the entire carburetor.

  • Air or Vacuum Leaks

Another reason for a surging mower is air or vacuum leaks. This happens when a loose carburetor draws in air through spaces around the spot connecting to the engine block.

The excess air renders the gasoline mixture out of balance, ruining the vacuum required to drag gasoline into the carb at the recommended flow rate. An easy fix is to tighten the bolts securing the carb until you feel firm resistance, then do the same to other bolts that connect the air intake to the engine.

Why Does My Walk Behind Mower Produce a Weird Noise? 

Your walk behind lawn mower can produce a screeching noise during mowing because of the following.  

  • Loose Belt

The drive belt is the leading reason a mower produces a screeching noise. The belt attaching the engine to the mower deck becomes loose and sticks between the guides.

Fixing the drive belt is very easy as you only need to retrieve it and align it where it belongs. 

  • An Obstacle Around the Blade

A lawn has many obstacles, so when mowing, something like a piece of string can get stuck on the blade, creating a weird noise. You can fix this by raising the rear of your mower to check for any impediment around the blades.

If you notice anything, remove it and run the mower to see if the sound disappears. 

  • Shaft Bearings

Shaft bearings need lubrication for the mower to operate smoothly. They’ll rub against the metal components and produce an unpleasant noise if dry.

If you have dry shaft bearings, locate them in the top part of the shaft, remove the cover, and add oil to them. 

  • Bent Blade

A bent blade produces a screeching sound as it touches the inside metal casing while spinning. Luckily, you can fix it by flipping the mower on its side, uninstalling the blade, and hammering it back to resume shape.

Avoid hammering the blade forcefully as you might break it. Also, ensure that you sharpen them and reinstall them back correctly. 

Why Does My Mower Run Then Die? 

There are various common and easy to fix reasons a mower runs then dies, including air loss to the engine and fuel restriction. When your mower blades encounter thick or tall grass, the carburetor comes in handy by increasing the fuel flow to the cylinder.

The increase in fuel allows the piston to continue firing exactly when the blades turn. So when your mower runs then dies, the likely problem is a decrease in fuel supply.

Insufficient airflow to the engine can also encourage your mower to run then die. Air blends with fuel to form a combustible solution in the cylinder. So if it’s limited, the fuel to air ratio won’t facilitate effective combustion hence your mower stalls. 

How Do You Know If Your Lawn Mower Engine Is Blown? 

Lawn mowers have engines that work with similar principles as with automobile engines. They can also break down when there is an improper balance of the essential elements for combustion. So how can you tell that your mower engine is blown? 

You can quickly tell that your mower engine is blown by examining the following signs:

  • Blue smoke.
  • White exhaust. 
  • Knocking sound in the engine. 
  • Blown piston. 
  • A hole in the engine block. 
  • Coolant in the engine oil. 
  • Blown rod. 
  • The engine won’t start.

What Happens If You Put Too Much Oil In a Lawn Mower? 

Overfilling your mower with oil presents various risks such as an oil leak, overheating, and a complex starting engine. Always confer with the user guide to know the prescribed oil level. 

When there’s too much oil in your mower engine and there’s resultant over heating, your mower is at a risk of major complications such as blowing of head gasket or hydro locking.

Why Is My Lawn Mower Blowing Smoke? 

Different type of smoke from your lawn mower explains the possible issue. For instance, when your mower blows black smoke, it means there is more fuel than air in the cylinder.

An incorrect blend of fuel and air causes incomplete combustion, so the unburnt fuel in the combustion chamber changes to smoke. 


A faulty or clogged air filter is the leading cause of black smoke in your mower. So you have to uninstall the faulty air filter to clean it or replace it.

Alternatively, try adjusting the carburetor to make a slighter fuel mixture if that doesn’t work. All you need is to turn a screw, but first, consult your user’s manual to be precise. 

On the other hand, a mower producing white smoke implies that the engine is burning oil. What happens is oil seeped into the combustion chamber when you tipped the mower to adjust or clean the blades.

Mowing on hilly terrain can also cause oil to sip into the combustion chamber. 

Lastly, if you notice excess blue or white smoke coming from your mower, it means the oil has a route to the combustion chamber. If that’s the case, your mower engine may sputter or stop.

The main culprit could be a crack in the breathing tube that delivers air from the combustion chamber to the exhaust port. So unless you have good knowledge of engines, this issue requires an experienced lawnmower mechanic. 

Can a Lawn Mower Battery Die While Mowing? 

A lawn mower battery is designed to produce enough power to crank the engine at startup. So once the engine runs, the charging system comes into play, ensuring your battery has the necessary power to crank the engine again. 

Despite these conveniences, a mower battery can still die while mowing for the following reasons. 

  • Old Battery

The lifespan of a mower is around four years. So as it approaches the end of its valuable days, it will fail to hold a charge, hence dying while mowing.

You will also notice that the electrical storage capacity of mower batteries is too small, meaning even a slight decrease in power can cause the battery to die while mowing.

So if your mower battery can’t hold a charge for around 1 or 2 weeks, it’s ready to fail and requires replacement. 

  • Recharging System 

A voltage regulator and an alternator form part of the electrical system that recharges a mower’s battery. If they get defective, they won’t have enough rpm to recharge your mower battery, causing it to die between mowing. 

  • Battery Post Corrosion

Corroded battery terminals are a sign of trouble, meaning your battery has loose connections. These loose connections make your battery work harder than usual, therefore draining power more quickly while mowing.

But cleaning the corroded terminals and tightening the loose connections will renew your battery’s ability to hold a charge. 

What Are The Symptoms of a Blown Head Gasket On a Lawn Mower? 

The role of a head gasket in lawn mowers is to prevent the oil and coolant from mixing. Your mower won’t operate at full power when the head gasket fails. Therefore, you need to know the symptoms of a blown head gasket so you can repair the mower in case of trouble. 

  • Oil Leak

All the head gasket seals in your lawn mower must be in good shape to keep normal compression levels in the engine. But with time, seals can dry out, become brittle, causing oil leaks around the head gasket seals.

This sign implies that the head gasket is blown, and you need to replace it to maintain optimal engine compression. 

  • Diminished Compression

A head gasket creates a vacuum seal in the engine’s combustion chamber. If it gets compromised, the combustion chamber can lose its vacuum seal, causing the head gasket to blow because pressure from the gasoline combustion leaks, providing insufficient power.

  • Smoke From the Exhaust

Plenty of smoke coming from the exhaust tells you that you have a blown head gasket. A blown gasket causes smoke because oil occupies the chamber where the fuel should fire. 

Why Did My Lawn Mower Backfire and Will Not Start? 

A lawnmower backfires when fuel ignites on the engine’s exterior inside the muffler. The backfiring makes a loud noise getting you off guard. However, the backfire won’t hurt your engine but signifies a mechanical problem. 

Backfiring Tips

  • After shut-off

A lawnmower can backfire immediately after shutting down. This happens due to incorrect carburetor settings and a compromised muffler. So checking your muffler and carburetor permits you to make the necessary adjustments and prevent backfiring. 

The gasoline you’re using could be another reason your mower backfires. Gas composed of alcohol ignites differently from non-alcohol gas. That means it can ignite in the muffler rather than the engine. 

  • During Shut-off

When your mower backfires as you shut down the engine, the most likely problem is that you have slowed down the engine speed quickly.

Mowing quickly across your lawn builds up the engine speed. Therefore, if you turn it off abruptly, the engine pumps gas into the muffler, causing it to ignite. 

You can prevent backfiring by slowly decreasing the engine speed and allowing the motor to idle for a while before shutting down the mower. 

  • When Starting


If your lawnmower backfires at startup, it means it is damaged either by a rock or other obstruction in your lawn. Today’s mowers feature safeguards to allow cheap parts like flywheels to break when the mower blade hits a barrier.

These cheap parts sacrifice themselves to save the costly ones like the crankshaft. When the flywheel breaks, your mower backfires when you start it. 

  • Special equipment 

Most mowers incorporate unique parts called anti-after fire solenoids that prevent backfire that occurs after shutting down the engine. This lets you shut down the engine at high speed without throwing excess fuel into the muffler.

So if this particular equipment is the cause of backfire, you will need a professional touch, so reach out to a certified repair facility for help. 

How Do I Know If My Lawn Mower Has a Blown Head Gasket? 

Performing a compression test is a sure way of confirming the suspicion of a blown gasket head. You can achieve this by measuring the internal pressure of the mower combustion chamber.

If the engine reads 60 psi and above, the compression pressure is within the recommended range. If the pressure is below 60 psi, apply a little engine oil into the spark plug hole to coat the pistons and cylinders.

After that, repeat measuring the pressure. If you can’t see any change in pressure, your mower head gasket is blown.  

Alternatively, check out the following steps: 

Step 1: Examine the General Symptoms

Before diagnosing the head gasket, ensure you recheck the symptoms to ensure you don’t repair something that’s not defective. A blown head gasket exhibits oil leaks through the filter cover, or the exhaust elicits white smoke. 

You will want to examine the spark plug for carbon deposits. If any, your head gasket is blown. 

Step 2: Remove the Engine Cover

The first thing when servicing a lawnmower is to remove the covers so you can access the engine and nearby components. First, determine where the bolts are to confirm the socket size.

Then use your socket wrench to unfasten the bolts. Place the bolts in a safe container, so they don’t get misplaced. After that, assess any electrical connection with the hood fan and discard it from the allotted connection clip. 

Step 3: Uninstall the Engine’s Carburetor, Filters, and Dipstick. 

The next step is to disassemble all the complementary parts surrounding the engine. 

First, locate the carburetor, filter, oil pipes, and fuel supply line. Begin by disengaging the fuel line ( close the pipe with a stopper.). Locate the carburetor and disconnect all its linkages and keep the screws safe. 

Next, disconnect the oil filter and pump connection. If your engine integrates a cooling system, disconnect those pipes. Lastly, take the precaution of placing a Collector pan or rags below these components to avoid spills. 

Step 4: Unscrew the Spark Plug

Use a torque wrench to unscrew the spark plug wire. 

Step 5:  Disassemble the Engine Head

You will find the engine head secured down onto the main engine block with mounting bolts. Once you find it, unfasten the bolts on its valve cover. Place a rag below to capture any oil present in the head. After that, remove the rocker mechanism and the push rod carefully. 

Lastly, unthread the screws around the head gasket, pull it off, and clean out any fuel spills. 

Step 6:  Check for Blows Around the Head.

A blown head gasket manifests three signs. 

  • A blown scuff around the area covered by the gasket. 
  • A blown or cracked layer of the head gasket. 
  • Traces of oil or coolant seep into the tank. 

Step 7: If Diagnosed As Blown, Replace the Gasket With a New One. 

If you have indications that your gasket is blown, replace it with a new one. If it’s not blown, reassemble all the components. But before that, ensure you clean all of these components. 

Lastly, test the mower to see if any problem persists. 


  • Avoid overtightening any bolts as you might damage the threads permanently. 
  • Always gap the spark plug before performing any checks. 

Here’s how to fix your lawn mower starting and dying problem:


A lawn mower is a piece of must-have equipment at your disposal. This machine can help you attain a rich green lawn courtesy of the powerful engines, mower blades, and other dedicated features.

However, the engine needs the right blend of fuel, air, and ignition spark for the mower to run smoothly. If this combination is out of balance, the mower starts misbehaving, and you will need to know…

Why Lawn Mower Starts Then Dies 

A lawn mower that starts the dies could be suffering from air and fuel restriction. As mentioned earlier, your mower needs the right blend of these two components for the engine to run smoothly. If not, your mower will start up well but die shortly. Other potential reasons include a faulty spark plug, a clogged air filter, and more. 

Thanks for sparing your time to read through this post, I hope all the information here meets your needs. If you have questions, please share them in the comment section below for further discussions. Meanwhile, enjoy mowing. 

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