Why Does My Lawn Mower Starts Then Dies?

As a mechanical specialist, I often encounter lawn mower owners who experience the frustrating issue of their lawn mower starting but dying off immediately. There could be several reasons behind this problem. I’m here to provide valuable insights into the common causes, various probable issues, and some helpful tips and tricks to help diagnose and resolve the problem quickly.

Why Does My Lawn Mower Starts Then Dies?

if you have a lawn mower that starts but dies immediately, the most common causes are:

1. Dirty or Clogged Carburetor

A dirty or clogged carburetor is one of the most common reasons a lawn mower starts and dies. The carburetor is responsible for mixing fuel and air in the correct proportions for combustion. If it is clogged with dirt or debris, the engine won’t receive the right mixture, causing it to stall.

Solution: Clean the carburetor using a cleaner spray or disassemble it and clean the components. It’s also a good idea to check the fuel and air filters, as these components can impact fuel and airflow to the carburetor.

2. Stale Fuel

Fuel tends to degrade and become stale over time due to the evaporation of volatile compounds. Stale fuel may cause the engine to start but then die quickly. This is a common issue if your lawn mower hasn’t been used for a while or stored over the winter with fuel in the tank.

Solution: Drain the old fuel from the tank and replace it with fresh fuel. Consider using a fuel stabilizer if you don’t plan to use the lawn mower for a while to prevent fuel degradation in the future.

3. Faulty Ignition Coil

The ignition coil is crucial for generating the high voltage required to ignite the fuel. A faulty ignition coil may prevent the engine from running properly or cause it to stall immediately after starting.

Solution: Test the ignition coil using a spark tester or multimeter. If it’s determined to be faulty, replace the ignition coil.

4. Blocked or Damaged Fuel Lines or Tank Vent

Blocked fuel lines, damaged hoses, or a clogged tank vent may restrict fuel flow to the carburetor, causing the engine to start but die quickly.

Solution: Inspect the fuel lines and hoses for any damage, and replace them if necessary. Additionally, check the tank vent and clean or replace it to ensure proper fuel flow.

5. Throttle or Choke Issues

The throttle or choke controls the engine’s air and fuel mixture flow. If it’s not functioning correctly, the engine may start but fail to keep running.

Solution: Inspect the throttle and choke mechanisms for damage or wear and replace any faulty parts. Additionally, ensure that the throttle and choke cables are properly connected and adjusted.

How To Clean a Dirty Lawnmower Carburetor?

Safety Precaution

Before we start with the guide to cleaning a lawnmower carburetor, it is crucial to emphasize the importance of safety. Ensure that the engine is turned off, the spark plug is disconnected, and you are wearing appropriate protective gear, such as gloves and safety glasses.

The Lawnmower Carburetor: Why It Needs Cleaning

A lawnmower carburetor is a key component in the internal combustion engine that mixes air and fuel in the proper proportions to ensure efficient combustion. Over time, carburetors can become clogged with debris, dirt, and gummed-up fuel deposits, which leads to decreased performance, poor fuel efficiency, and even engine failure. To avoid these problems and keep your lawnmower running smoothly, it is essential to clean the carburetor periodically.

Cleaning Your Lawnmower Carburetor: Step-by-Step Guide

Tools and Materials

To clean your lawnmower carburetor, you will need the following tools and materials:

  • Wrench
  • Screwdriver set (including flathead and Phillips’s head)
  • Carburetor cleaner
  • Compressed air (optional)
  • Container for fuel
  • Clean rags
  • Rubber gloves
  • Safety glasses

Step 1: Removing the Carburetor

  1. First, locate the carburetor on your lawnmower. It is typically connected to the air filter and the fuel line.
  2. Disconnect the fuel line from the carburetor. Use a container to catch any fuel that may spill.
  3. Remove the air filter to access the carburetor. Depending on your lawnmower model, you may need a screwdriver or wrench to do this.
  4. Unscrew the bolts that hold the carburetor in place, using either a wrench or a screwdriver, and gently remove the carburetor from the engine.

Step 2: Cleaning the Carburetor

  1. Put on your rubber gloves and safety glasses. Using a carburetor cleaner, spray all parts of the carburetor externally, paying particular attention to areas with visible debris and dirt.
  2. Disassemble the carburetor by removing all screws, gaskets, and valves. Please keep track of the order in which you remove them to make reassembly easier.
  3. Immerse the carburetor components in the cleaner and let them soak for at least 30 minutes.
  4. Once the parts are soaked, carefully wipe down each piece with a clean, lint-free rag. For stubborn dirt and grime, you can use a soft-bristle brush.
  5. If available, use compressed air to blow out any remaining debris or cleaner from the small holes and crevices of the carburetor components.
  6. Allow the parts to air-dry entirely before proceeding to reassembly.

Step 3: Reassembling the Carburetor and Testing the Engine

  1. Reassemble the carburetor by reversing the order in which you removed the components. Ensure all gaskets, valves, and screws are securely fastened.
  2. Reattach the carburetor to the engine, reconnect the fuel line, and reinstall the air filter.
  3. Connect the spark plug back into the engine.
  4. Start the lawnmower and let it run for a few minutes to test its performance. If the engine operates smoothly and efficiently, the cleaning process is successful.

How To Stop Your Lawnmower Carburetor From Clogging?

The best way to prevent a clogged lawnmower carburetor is by using fuel stabilizers. These additives help reduce the gumming of fuel and form deposits in the carburetor, which can cause it to become clogged.

Replacing your air filter regularly and keeping it clean can help prevent clogging and ensure optimal engine performance. Finally, draining and replacing old fuel with fresh fuel can also help reduce the build-up of deposits in the carburetor. Following these simple tips will ensure your lawnmower runs smoothly and efficiently for years.


Why does Briggs and Stratton’s engine run then dies?

This could be due to several issues, such as fuel delivery problems, faulty ignition coil, blocked or damaged fuel lines or tank vent, throttle or choke problems, and more. Inspecting the engine components and taking corrective action as needed is best. Cleaning the carburetor periodically may also be necessary to prevent it from clogging.

What is a fuel stabilizer?

A fuel stabilizer is an additive that helps reduce the gumming of fuel and form deposits in the carburetor. It can help prevent clogging of the carburetor and ensure optimal engine performance. It can also be used to extend the life of stored fuel.


Maintaining your lawnmower carburetor is essential for optimal engine performance, which is why periodic cleaning is recommended. Cleaning your lawnmower carburetor requires removing the carburetor from the engine, cleaning it with a cleaning solution or compressed air, and reassembling it back into the engine.

For best results, use fuel stabilizers and replace your air filter regularly. Additionally, draining and replacing old fuel with fresh fuel can also help reduce the build-up of deposits in the carburetor. Taking these steps will help ensure that your lawnmower runs smoothly and efficiently for years to come.

Thank you for taking the time to read about how to clean a dirty lawnmower carburetor! We hope this guide has been helpful & you got the answer about why does my lawn mower start then die. Please reach out if you have any additional questions or need assistance with cleaning your own carburetor.

Always remember to wear proper protective gear, such as gloves and safety glasses, when working on any lawnmower components. Stay safe!


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