How to Fix Common Lawn Mower Engine Problems and Get Your Mower Running Smoothly

Our Lawn Mower Repair Service

Key Takeaways

The most common lawn mower engine problems are failure to start, loss of power, and engine surging, all of which are usually caused by issues with the spark plug, fuel system, or air filter.

What You Need to Know

• Starting Issues: If your mower won’t start, the problem is most often a lack of spark (bad spark plug), a lack of fuel (clogged carburetor or filter), or old, stale gasoline.
• Loss of Power: This usually signals a clogged air filter or an engine that’s not getting enough fuel, causing it to struggle under a load.
• Engine Surging: An engine that revs up and down on its own is a classic sign of a lean fuel mixture, almost always due to a dirty carburetor.

How to Diagnose and Fix the Problem

Step 1: Check the Spark Plug — Ensure a Strong Spark

A clean, properly gapped spark plug is essential for ignition. Remove the spark plug with a socket wrench and inspect it. If it’s covered in black carbon, wet with fuel, or the porcelain is cracked, it needs to be replaced. A worn or dirty plug won’t create a strong enough spark to ignite the fuel-air mixture.

Step 2: Inspect the Air Filter — Maintain Proper Airflow

A clogged air filter is one of the most common causes of engine problems. A dirty filter restricts airflow, causing the engine to run “rich” (too much fuel, not enough air), which leads to a loss of power and poor performance. Replace a paper filter if it’s dirty or clean a foam filter with soap and water before letting it air dry.

Step 3: Address the Fuel System — The Most Likely Culprit

The fuel system is the source of most common engine issues, especially those related to surging or starting.

• Old Fuel: If your mower has sat with old gas for a few months, it’s likely the fuel has separated and left behind gummy deposits. Drain the old gas and replace it with fresh fuel.
• Clogged Filter: Locate your fuel filter (it’s a small canister along the fuel line) and check if it’s dirty or clogged. Replace it if it is.
• Dirty Carburetor: If the mower surges or won’t start, the tiny passages in the carburetor are likely clogged with fuel residue. This is the most common and difficult fix. You’ll need to remove the carburetor and clean it thoroughly with a specialized carburetor cleaner spray.

A Good-to-Know Tip: The Importance of Fresh Fuel

Using fresh gasoline is one of the most effective ways to prevent engine problems. Gasoline, especially the ethanol-blended type, can degrade in as little as 30 days. As it degrades, it leaves behind sticky varnish and gum deposits that clog the tiny fuel passages inside your carburetor. To avoid this, use a fuel stabilizer like STA-BIL if you plan on storing fuel for more than a month, and always use fresh fuel at the start of the mowing season.

Lawn Mower Engine Repair Service in Louisiana

If you’re in the Louisiana ( Baton Rouge and Gonzales specifically ) area and need professional help with your lawn mower engine, Gautreaux’s Outdoor Power offers expert diagnostics and repair services. Our certified technicians can quickly identify and fix starting, power, and surging issues, getting your mower back in peak condition for a reasonable price. We stock a full range of replacement parts for all major brands, including Briggs & Stratton, Honda, and Kohler.

Client Reviews

• “Took care of me like i was their only customer. Mower was brought in for repair estimate they found it was still under warranty and jumped on it. They kept in communication through the entire process and went over the mower and found other things that needed to fixed and knocked those out too. Great friendly people” – Mike Durkin S.
• “Very helpful and knowledgeable about my service. Needed and was kept informed throughout the process.” – Andree’ Guillory

 

FAQ

Q: Why does my lawn mower engine surge up and down?

A: This is typically caused by a lean fuel mixture, which means there’s not enough fuel getting to the engine. The most common cause is a dirty carburetor, but it can also be a clogged fuel filter or an air leak in the fuel system.

Q: Can old gas cause my mower to stall?

A: Yes, absolutely. Old, stale gasoline can leave varnish and gum deposits in the carburetor, clogging the small passages and causing the engine to stall under load or not start at all.

Q: Is it okay to use a lawn mower with a surging engine?

A: It’s not recommended. Continuing to operate a surging engine can lead to a less efficient cut, increased emissions, and potential long-term damage due to an improper air-fuel ratio. It’s best to fix the problem promptly.