A surging lawn mower can be frustrating and inefficient. If your Husqvarna mower’s engine revs up and down repeatedly, or “hunts” while running, it indicates that something is disrupting the smooth flow of fuel, air, or the spark. I’ve experienced this with my own mower, and the good news is, it’s usually caused by a few common issues. Let’s explore what could be causing your Husqvarna mower to surge and how to fix it.
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Common Causes of Engine Surging
1. Clogged or Dirty Carburetor
A clogged carburetor is one of the most frequent causes of engine surging. Over time, old fuel, dirt, or debris can clog the small jets inside the carburetor, leading to an inconsistent fuel-air mixture that causes the engine to surge.
How to Fix It:
- Clean the carburetor: Remove the carburetor and clean it thoroughly with a carburetor cleaner. Pay special attention to the jets and other small openings.
- Use fresh fuel: Old or stale fuel can cause buildup inside the carburetor. Always use fresh fuel to prevent clogging.
2. Old or Stale Fuel
Fuel degrades over time, and old gas can cause engine surging due to the breakdown of its components. Ethanol in gasoline can attract moisture, which leads to corrosion and fuel quality issues.
How to Fix It:
- Drain old fuel: If your mower has been sitting for a long time, drain the old fuel and replace it with fresh gas.
- Add fuel stabilizer: Use a fuel stabilizer to keep the fuel fresh and prevent moisture build-up, especially if the mower is going to sit for extended periods.
3. Airflow Problems (Dirty Air Filter)
A clogged air filter can restrict airflow to the engine, leading to a rich fuel mixture (too much fuel and not enough air), which can cause the engine to surge. Regularly checking and cleaning or replacing the air filter helps the mower run smoothly.
How to Fix It:
- Inspect the air filter: Remove the air filter and check for dirt or debris.
- If the filter is dirty, clean it (for foam filters) or replace it (for paper filters).
- A clogged air filter often leads to more unburnt fuel in the system, contributing to inconsistent engine behavior.
4. Fuel Line or Filter Blockage
The fuel line or fuel filter can become blocked by debris or dirt, leading to an irregular fuel supply. This can cause the engine to surge because it’s not receiving a steady flow of fuel.
How to Fix It:
- Inspect the fuel line: Check for any kinks, leaks, or blockages in the fuel line. Replace the line if it’s damaged or clogged.
- Replace the fuel filter: If the fuel filter is dirty or blocked, replace it with a new one to restore proper fuel flow.
5. Governor Issues
The governor is a mechanical device that regulates the engine speed. If the governor is damaged or misadjusted, it can cause the engine to surge as it constantly tries to correct the engine speed.
How to Fix It:
- Inspect the governor springs: Check for any broken or misaligned springs or linkages in the governor system.
- If the governor appears damaged or is misadjusted, you may need to refer to your mower’s manual or seek professional help to adjust it properly.
6. Vacuum Leaks
A vacuum leak in the carburetor or intake manifold can cause inconsistent engine performance. The leak disrupts the balance of air and fuel entering the engine, causing surging.
How to Fix It:
- Inspect the carburetor gasket and intake manifold for cracks, wear, or leaks. If you find any issues, replace the damaged parts.
7. Dirty or Faulty Spark Plug
A fouled or faulty spark plug can cause inconsistent firing, leading to engine surging. If the spark plug is dirty, corroded, or damaged, it won’t ignite the fuel mixture properly, causing surges in the engine’s performance.
How to Fix It:
- Remove and inspect the spark plug: Clean or replace the spark plug if it’s dirty, corroded, or worn out.
- Make sure the spark plug is properly gapped to the specifications listed in your mower’s manual.
Preventing Future Surging Issues
To avoid engine surging in the future, it’s essential to keep up with regular maintenance:
- Change the oil and air filter regularly.
- Use fresh fuel and add a stabilizer if the mower will sit for a while.
- Inspect the carburetor, fuel lines, and spark plug as part of your routine checks.
- Store your mower properly to prevent debris from clogging components.
Conclusion
If your Husqvarna lawn mower is surging, it’s likely caused by a fuel, air, or spark-related issue. Start by checking the carburetor, air filter, fuel lines, and spark plug. Cleaning or replacing these parts can often solve the problem. Regular maintenance is key to preventing engine surging and keeping your mower running smoothly for years to come.