Ariens Lawn Mower Won’t Start

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By Kirsi Jansa

Ariens is a well-known brand in the outdoor power equipment industry. Ariens produces various products, including snow blowers, garden tractors, and lawn mowers. Founded in 1933, the company has a long-standing reputation for building durable and reliable machinery.

Ariens lawn mowers are often recognized for their durability and performance. They offer walk-behind and zero-turn mowers, which are particularly popular among professionals and homeowners with larger lawns due to their speed and maneuverability.

Ariens Lawn Mower

12 Common Reasons your Ariens Gas Lawn Mower won’t Start

Empty Fuel Tank or Stale Fuel

If your Ariens lawn mower has an empty or stale fuel tank, it may not start. The engine requires fresh gasoline to ignite and run. Stale fuel can degrade over time, losing its combustibility and causing gumming or varnish-like deposits.

How to Fix: To remedy the issue, ensure your fuel tank is filled with fresh gasoline. If you suspect the fuel is stale, empty the tank and refill it with fresh fuel. For optimal performance, consider adding a fuel stabilizer when storing the mower for extended periods.

Spark Plug Issues

The spark plug is essential for igniting the fuel-air mixture in the engine. If it’s fouled, damaged, or has an improper gap, your Ariens lawn mower might not start or may run erratically.

How to Fix: Inspect the spark plug for signs of wear or damage. Clean any deposits with a wire brush and check the gap using a gap tool. If the plug is old or damaged, replace it with a new one specific to your mower’s model. Ensure the spark plug is seated correctly, and the wire is connected securely.

Fuel Cap Vent Problems

The fuel cap vent allows air into the fuel tank, balancing the pressure as fuel is consumed. If the vent gets blocked, it creates a vacuum inside the tank, preventing fuel from flowing to the carburetor, causing the mower to run sporadically or stop running altogether.

How to Fix: Inspect the fuel cap for any visible blockages and clean them. You can test for a clogged vent by loosening the fuel cap slightly and then trying to start the mower. If it runs better, the vent may be the issue. If cleaning doesn’t resolve the problem, consider replacing the fuel cap with a new one designed for your Ariens model.

Fuel Cap Vent Problems

Bad Fuel Pump

The fuel pump delivers fuel from the tank to the carburetor. If the pump malfunctions, it might lead to inadequate or no fuel supply, preventing the engine from starting or causing it to run poorly.

How to Fix: To diagnose a faulty fuel pump, try starting the mower after priming the carburetor directly with a small amount of fuel. The pump might be the issue if it starts briefly and then dies. Consider cleaning the fuel pump or replacing it entirely depending on the mower’s design. Ensure that all fuel lines are free of obstructions and connected properly.

Air Filter Blockage

A clogged or dirty air filter restricts airflow into the engine, disrupting the proper air-fuel mixture. This can hinder the engine’s performance, make it run rich, or even prevent it from starting.

How to Fix: Inspect the air filter. If it’s mildly dirty, you can clean it using soapy water (for foam filters) or by tapping out the dirt (for paper filters). Allow it to dry completely before reinstalling. If the air filter is heavily clogged or damaged, replace it with a new one. Ensure the filter sits properly in its housing to prevent unfiltered air from entering the engine.

Blocked Fuel Pump

A blocked fuel pump hinders the flow of gasoline from the fuel tank to the carburetor. This can prevent the engine from receiving the necessary fuel, causing difficulty starting or erratic engine performance.

How to Fix: Begin by disconnecting the fuel lines and carefully inspecting them for any obstructions. Clean or replace any dirty or clogged fuel filters. Examine the pump itself: in some cases, debris can accumulate inside. Clean the pump thoroughly, ensuring all passageways are free of blockages. After cleaning or replacing the necessary components, reconnect the fuel lines, ensuring a secure fit.

Fuel Pump

Carburetor Issues

The carburetor is responsible for mixing the correct ratio of fuel and air for combustion. Dirt, gumming, or misadjustments can disrupt this balance, leading to problems like hard starting, stalling, or erratic engine behavior.

How to Fix: If you suspect carburetor issues, clean it. Remove the carburetor, disassemble it, and clean all parts using carburetor cleaner. Pay special attention to jets and passageways. After cleaning, reassemble and reinstall. If problems persist, you may need to adjust the carburetor settings or consider replacing it with a new one if it’s excessively worn or damaged.

Faulty Ignition Coil

The ignition coil generates the voltage to spark the plug and ignite the fuel-air mixture. A faulty ignition coil may lead to a weak or no spark, preventing the mower from starting or causing it to run erratically.

How to Fix: To diagnose a faulty ignition coil, use an ignition tester to check for spark. The coil may be the culprit if the spark is weak or non-existent. Before replacing, ensure all connections to the coil are secure and free from corrosion. If the ignition coil is faulty, replace it with a new one specific to your mower’s model. Ensure all connections are secure upon reinstallation.

Bad Safety Switch

Safety switches are designed to prevent the mower from starting or operating under potentially unsafe conditions, such as when the mower deck is engaged or when the user is not in the seat. A malfunctioning safety switch can prevent the mower from starting even when conditions are safe.

How to Fix: Start by identifying the safety switches on your mower, commonly found on the seat, clutch, and mower deck. Test each switch for proper operation. If a switch is faulty, it might need adjustment or replacement. Always refer to the mower’s manual for specifics on testing and replacing safety switches. Ensure that all connections are resecured and free from corrosion upon reinstallation.

Bad Safety Switch

Water in the Fuel

Water contamination in the fuel can hinder the proper combustion process. Water doesn’t ignite like gasoline, so if it reaches the engine, it can cause sputtering, poor performance, or even prevent the mower from starting.

How to Fix: Drain the old fuel from the tank if you suspect water contamination. Remove and clean or replace the fuel filter. Refill the tank with fresh gasoline. Clean the carburetor may also be necessary, as water and any potential sediment can settle there. To prevent future contamination, store your fuel in a clean, dry place and avoid leaving the mower’s fuel cap open during rainy or humid conditions.

Dead or Weak Battery (For Electric Start Models):

A dead or weak battery will not provide the necessary power to turn over the engine for mowers with an electric start feature. This results in a slow cranking sound or no response when starting the mower.

How to Fix: If the battery is weak or dead, charge it using a suitable charger. Check the battery terminals for corrosion and clean them if necessary. Ensure all connections are tight and secure. If the battery consistently loses its charge or is older than its recommended lifespan, consider replacing it with a new one. Regularly check the charging system of the mower to ensure the battery is being charged while the engine is running.

Sheared Flywheel Key

The flywheel key is a small metal piece that aligns the flywheel’s timing with the engine’s crankshaft. If the mower blade hits a hard object (like a rock or root), it can cause the flywheel key to shear. This disrupts the engine’s timing, causing poor performance, backfiring, or preventing the engine from starting.

How to Fix: To address a sheared flywheel key, you’ll need to remove the mower’s flywheel. Once accessed, inspect the key for damage. If it’s sheared or bent, replace it with a new one. When reassembling, ensure that the flywheel and crankshaft alignment notches match up. Tighten the flywheel nut to the proper torque specification to prevent the key from shearing again.

Sheared Flywheel Key

Ariens Lawn Mower Still Won’t Start: Seek Professional Help

If you’ve exhausted the common troubleshooting steps and your Ariens lawn mower still won’t start, it might have a more complex underlying issue. In such cases, consulting with a professional lawn mower technician or mechanic is advisable. They possess specialized knowledge and tools to accurately diagnose and fix the problem, ensuring the mower’s longevity and optimal performance.

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