Lawn mowers are essential tools for maintaining a well-kept lawn, but they can sometimes exhibit frustrating behavior, such as revving up and down. This issue, often referred to as “surging,” can be caused by a variety of factors. In this article, we will explore the common causes of this problem, provide troubleshooting steps, and offer preventive measures to keep your lawn mower running smoothly.
Common Causes of Lawn Mower Surging
Dirty Fuel
One of the most common reasons for a lawn mower to rev up and down is dirty fuel. Over time, gasoline can degrade, especially if it has been sitting in the tank for an extended period. As gasoline degrades, it can form varnish and sediment that clog the fuel lines, filter, and carburetor. This restricts the flow of fuel to the engine, causing it to surge.
Solution
Drain the old fuel from the tank and replace it with fresh gasoline. Consider using a fuel stabilizer to prevent the gasoline from degrading too quickly.
Clogged Fuel Filter
A clogged fuel filter is another common cause of engine surging. The fuel filter is designed to remove impurities from the gasoline before it reaches the engine. If the filter becomes clogged, it can restrict the flow of fuel, leading to fluctuating RPMs.
Solution
Inspect the fuel filter and replace it if it is clogged or dirty. This is a relatively simple and inexpensive fix that can significantly improve your lawn mower’s performance.
Air Leaks in the Fuel Line
Air leaks in the fuel line can also cause the engine to rev up and down. When air enters the fuel line, it can create a vacuum that restricts the flow of fuel to the engine. This can cause the engine to struggle, leading to surging.
Solution
Examine the fuel lines for any signs of wear or damage. If you find any air leaks, repair or replace the affected fuel lines.
Spark Plug Issues
A faulty or incorrectly gapped spark plug can cause the engine to run unevenly. The spark plug is responsible for igniting the fuel-air mixture in the engine. If the spark plug is not functioning correctly, it can lead to incomplete combustion, causing the engine to surge.
Solution
Inspect the spark plug for any signs of damage or wear. If the spark plug is damaged, replace it with a new one. Additionally, ensure that the spark plug is correctly gapped according to the manufacturer’s specifications.
Air Filter Problems
A dirty or clogged air filter can restrict airflow to the engine, leading to performance issues. The air filter is designed to prevent dirt and debris from entering the engine. If the filter becomes clogged, it can reduce the amount of air reaching the engine, causing it to surge.
Solution
Clean the air filter or replace it if it is too dirty. Regularly checking and maintaining the air filter can prevent this issue from occurring.
Carburetor Issues
An improperly adjusted carburetor can cause the engine to surge. The carburetor is responsible for mixing the correct amount of fuel and air for combustion. If the carburetor is not adjusted correctly, it can lead to an uneven fuel-air mixture, causing the engine to rev up and down.
Solution
Ensure that the carburetor is properly adjusted according to the manufacturer’s specifications. If you are unsure how to adjust the carburetor, consult the owner’s manual or seek professional assistance.
Troubleshooting Steps
Check Fuel Quality
The first step in troubleshooting a surging lawn mower is to check the fuel quality. Old or contaminated gasoline can cause a variety of engine problems, including surging.
Steps
Drain the old fuel from the tank.
Replace it with fresh gasoline.
Consider using a fuel stabilizer to prevent future issues.
Inspect Fuel Filter
Next, inspect the fuel filter to ensure it is not clogged or dirty.
Steps
Locate the fuel filter (refer to the owner’s manual if necessary).
Remove the fuel filter and inspect it for any signs of clogging or dirt.
Replace the fuel filter if it is clogged or dirty.
Examine Fuel Lines
After checking the fuel filter, examine the fuel lines for any air leaks.
Steps
Inspect the fuel lines for any signs of wear or damage.
If you find any air leaks, repair or replace the affected fuel lines.
Check Spark Plug
The next step is to check the spark plug for any signs of damage or incorrect gap.
Steps
Remove the spark plug using a spark plug wrench.
Inspect the spark plug for any signs of damage or wear.
If the spark plug is damaged, replace it with a new one.
Ensure that the spark plug is correctly gapped according to the manufacturer’s specifications.
Clean or Replace Air Filter
After checking the spark plug, clean or replace the air filter.
Steps
Locate the air filter (refer to the owner’s manual if necessary).
Remove the air filter and inspect it for any signs of dirt or clogging.
Clean the air filter if it is dirty, or replace it if it is too dirty.
Adjust Carburetor
Finally, adjust the carburetor to ensure it is properly set according to the manufacturer’s specifications.
Steps
Locate the carburetor (refer to the owner’s manual if necessary).
Adjust the carburetor according to the manufacturer’s specifications.
If you are unsure how to adjust the carburetor, consult the owner’s manual or seek professional assistance.
Preventive Measures
Use Fresh Fuel
One of the best ways to prevent your lawn mower from surging is to use fresh fuel. Old or contaminated gasoline can cause a variety of engine problems, including surging.
Tips
Always use fresh gasoline in your lawn mower.
Avoid letting gasoline sit in the tank for extended periods.
Consider using a fuel stabilizer to prevent the gasoline from degrading too quickly.
Store Properly
Proper storage is essential for maintaining your lawn mower’s performance. Storing your lawn mower in a dry, covered area can prevent moisture and debris from entering the fuel system.
Tips
Store your lawn mower in a dry, covered area.
Use a lawn mower cover to protect it from the elements.
Avoid storing your lawn mower in areas with high humidity or temperature fluctuations.
Regular Maintenance
Regular maintenance is key to preventing issues with your lawn mower. By performing routine checks and maintenance, you can keep your lawn mower running smoothly and avoid problems like surging.
Tips
Perform regular maintenance, such as cleaning the air filter and checking the fuel system.
Follow the manufacturer’s recommended maintenance schedule.
Keep a maintenance log to track when you performed maintenance and what was done.
Conclusion
A lawn mower that revs up and down can be frustrating to deal with, but understanding the common causes and knowing how to troubleshoot the issue can help you get your lawn mower back in working order. By following the preventive measures outlined in this article, you can keep your lawn mower running smoothly and avoid future issues. Regular maintenance, using fresh fuel, and proper storage are key to ensuring your lawn mower performs at its best. With these tips, you can enjoy a well-maintained lawn without the hassle of a surging lawn mower.
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