Is Your Lawn Mower Surging? Here’s How to Fix It!

The hum of a well-maintained lawn mower is a symphony of summer, a relaxing soundtrack to a well-kept lawn. But when that symphony turns into a jarring, erratic surge, the joy of mowing turns into frustration. A surging lawn mower, characterized by sudden increases in engine speed, can be a real pain – and potentially dangerous. But don’t despair! This article will take you through the common causes of lawn mower surges, and provide you with practical solutions to get your mower back in smooth, efficient working order.

In a nutshell, a surging lawn mower typically points to an issue with either the carburetor, fuel system, or ignition system. By understanding these potential culprits and following our troubleshooting steps, you’ll be back to mowing with a steady, reliable machine in no time.

The Root of the Problem: Understanding Lawn Mower Surges

A surging lawn mower is essentially a symptom of an engine that’s not getting the right fuel/air mixture at the right time. The most common culprits are:

  • Carburetor Problems: The carburetor is responsible for mixing fuel and air before it enters the engine. A dirty carburetor, a worn-out needle valve, or a faulty float can disrupt this delicate balance, causing the engine to surge.
  • Fuel System Issues: Dirty fuel lines, a clogged fuel filter, or a faulty fuel pump can hinder the flow of fuel to the carburetor, leading to surges.
  • Ignition System Malfunctions: Problems with the spark plug, ignition coil, or wiring can disrupt the spark timing, causing the engine to run erratically.

Diagnosing the Issue: Where to Start Your Troubleshooting

Before diving into repairs, it’s important to accurately identify the source of the problem. Here’s a step-by-step approach:

1. Inspect the Fuel System

a. Check the Fuel Lines and Filter:

* Look for cracks, leaks, or blockages in the fuel lines. 
* Inspect the fuel filter for dirt or debris. If it's clogged, replace it. 
* Consider replacing the entire fuel line if it appears worn or brittle.

b. Examine the Fuel Tank and Pump:

*  Ensure the fuel tank is clean and free of debris.
*  If your mower has a fuel pump, check for leaks or signs of malfunction.

2. Check the Carburetor

a. Inspect the Air Filter:

*  A dirty air filter restricts airflow, affecting the fuel/air mixture. 
*  Clean or replace the air filter as needed.

b. Check for Leaks or Blockages:

*  Examine the carburetor for any visible leaks. 
*  Check for blockages in the carburetor's jets or passages.

3. Inspect the Ignition System

a. Examine the Spark Plug:

*  Replace a worn or fouled spark plug. A dirty or corroded plug can impede the spark.

b. Check the Ignition Coil and Wiring:

*  Look for cracks, breaks, or loose connections in the wiring.
*  Ensure the ignition coil is securely attached and in good working order.

Fixing the Surging: Step-by-Step Solutions

Once you’ve identified the culprit, you can address the issue with these practical solutions:

1. Cleaning the Carburetor

a. Disassembly and Cleaning:

*  Remove the carburetor from the engine.
*  Disassemble the carburetor carefully, noting the order of parts. 
*  Clean all parts thoroughly with carburetor cleaner. 
*  Use a small brush or compressed air to remove stubborn debris.

b. Reassembly and Adjustment:

*  Reassemble the carburetor, ensuring all parts are properly seated.
*  Adjust the carburetor settings as needed. Consult your owner's manual for specific adjustment instructions.

2. Replacing the Fuel System Components

a. Replacing the Fuel Filter:

*  Locate the fuel filter and disconnect the fuel lines.
*  Install a new fuel filter of the correct type and size.
*  Reconnect the fuel lines securely.

b. Replacing the Fuel Lines:

*  Replace the fuel lines if they are cracked, brittle, or leaking. 
*  Ensure the new fuel lines are compatible with your mower.

3. Fixing Ignition System Issues

a. Replacing the Spark Plug:

*  Remove the old spark plug and install a new one of the correct type.
*  Tighten the spark plug securely.

b. Repairing or Replacing Wiring:

*  Repair any damaged or frayed wiring.
*  Replace the entire wiring harness if necessary.

Preventing Surging: Maintenance is Key

Regular maintenance is essential to prevent future surging problems. Here are some tips:

  • Clean the Air Filter Regularly: A clean air filter is crucial for optimal engine performance.
  • Use Fresh Fuel: Old gas can gum up the carburetor and fuel lines.
  • Change the Fuel Filter Annually: Replace the fuel filter at least once a year, or more frequently if you use the mower extensively.
  • Perform Routine Inspections: Check the fuel lines, carburetor, and ignition system for any signs of wear or damage.

When to Call a Professional

If you’re not comfortable working on your lawn mower, or if the problem persists despite your efforts, it’s best to call a qualified mechanic.

By understanding the causes of lawn mower surges and following these troubleshooting steps, you can tackle the problem head-on and get your mower running smoothly again. Remember, a well-maintained lawn mower is a happy mower, and a happy mower means a happy lawn!


1. What is a lawn mower surge?

A lawn mower surge is a sudden increase in engine speed, often accompanied by a change in sound, like a “blip” or a “pop.” This can happen when you’re mowing your lawn, but it can also happen when you’re idling or accelerating. It’s a common problem that can be frustrating, but it’s usually easy to fix.

The surge can be caused by a variety of factors, including a clogged air filter, a dirty carburetor, a faulty spark plug, or a fuel problem. To determine the root cause, you’ll need to inspect the lawn mower and identify the potential culprit. By addressing these issues, you can restore your lawn mower to its smooth and consistent operation.

2. What are the potential causes of lawn mower surging?

There are several reasons why your lawn mower might be surging. Some of the most common causes include:

  • A clogged air filter: This can restrict airflow to the engine, leading to an uneven fuel mixture and surging.
  • A dirty carburetor: This can cause the engine to receive an inconsistent fuel supply, leading to surging.
  • A faulty spark plug: This can cause misfires and inconsistent combustion, leading to surging.
  • Fuel problems: Dirty fuel or a clogged fuel filter can also cause surging.

Identifying the specific issue is key to successfully resolving the surging problem and ensuring your lawn mower operates smoothly.

3. How can I fix a lawn mower that is surging?

There are several steps you can take to fix a lawn mower that is surging. Here are a few:

  • Check and clean the air filter: A dirty air filter can restrict airflow to the engine, causing it to surge. Remove the air filter and clean it with soap and water, or replace it with a new one.
  • Clean the carburetor: A dirty carburetor can also cause surging. To clean the carburetor, you can use a carburetor cleaning kit or take it to a professional for cleaning.
  • Check and replace the spark plug: A faulty spark plug can cause misfires and surging. Inspect the spark plug for wear or damage, and replace it if necessary.
  • Check the fuel system: Dirty fuel or a clogged fuel filter can also cause surging. Ensure the fuel is fresh and free of debris, and check the fuel filter for any blockages.

By addressing these potential issues, you can often resolve the surging problem and restore your lawn mower to its optimal performance.

4. How do I know if my air filter is the problem?

A clogged air filter is a common cause of lawn mower surging. You can tell if the air filter is the problem by inspecting it for dirt and debris. If the air filter is dirty or clogged, it’s likely restricting airflow to the engine, causing it to surge.

To ensure the air filter is the issue, replace the filter with a new one and test the lawn mower. If the surging stops, you’ve identified the problem. If the surging persists, it’s likely a different issue requires attention.

5. How do I clean the carburetor on my lawn mower?

Cleaning a lawn mower carburetor can be a bit tricky, but it’s a common DIY fix for surging problems. You’ll need a carburetor cleaning kit and some patience.

Begin by disconnecting the fuel line and removing the carburetor from the engine. Then, use the cleaning kit to spray the carburetor with cleaning solution. Once you’re done, reassemble the carburetor and reconnect the fuel line. If the surging continues, it’s best to consult a professional for further assistance.

6. How often should I check my spark plug?

It’s generally recommended to check your spark plug every 25 hours of use. However, if you notice any signs of engine trouble, such as surging, it’s a good idea to check the spark plug sooner.

To inspect the spark plug, simply remove it and look for signs of wear or damage. If the spark plug is worn or damaged, replace it with a new one. Regular inspection and replacement of spark plugs can help prevent engine issues and ensure optimal lawn mower performance.

7. Can I fix a surging lawn mower myself, or should I take it to a professional?

While many common lawn mower surging problems can be fixed with simple DIY solutions, some more complex issues may require professional assistance.

If you’re comfortable working on small engines and have the necessary tools, you can likely fix the problem yourself. However, if you’re not comfortable working on engines or the issue seems complicated, it’s best to take your lawn mower to a qualified professional. They have the experience and expertise to diagnose the issue and recommend the best course of action.

Leave a Comment