A trusty Bolens lawn mower is a valuable asset for maintaining a pristine yard, but even the most reliable machines can occasionally encounter problems. When your Bolens isn’t performing as it should, a systematic approach to troubleshooting can save you time, money, and frustration. Understanding the common issues, from a mower that won’t start to one that runs poorly, is the first step toward a successful repair. This guide will walk you through a logical sequence of diagnostics, ensuring you cover the essential components and potential culprits. We’ll delve into fuel, ignition, air, and electrical systems, providing practical advice to get your Bolens back to peak operating condition, transforming you from a puzzled owner into a confident mechanic.
Preparing to troubleshoot: Safety and initial checks
Before you begin any diagnostic work on your Bolens lawn mower, safety must be your top priority. Always disconnect the spark plug wire to prevent accidental starting, and ensure the engine is cool. Wear appropriate personal protective equipment, such as gloves and eye protection. Once safety measures are in place, start with the most basic and often overlooked checks, as these can frequently resolve a myriad of problems without deeper investigation.
- Fuel level and quality: Is there enough fuel in the tank? More importantly, is it fresh fuel? Stale gasoline, especially after sitting for extended periods, can degrade and cause starting or running issues. Old fuel can gum up the carburetor. If the fuel is suspect, drain the tank and refill with fresh, ethanol-free gasoline if possible.
- Engine oil level: Check the oil dipstick. Low oil levels can trigger safety shutdowns or cause significant engine damage if ignored. Most modern mowers have a low-oil sensor that prevents starting.
- Air filter: A clogged air filter can restrict airflow, causing the engine to run rich, lose power, or fail to start. Remove the air filter and inspect it. If it’s dirty or saturated with oil, clean it (if it’s a foam filter) or replace it (for paper filters).
- Spark plug wire: Ensure the spark plug wire is securely attached to the spark plug. A loose connection can prevent ignition.
- Safety interlock switches: Bolens mowers, like all modern mowers, have safety switches designed to prevent operation under unsafe conditions. Check that the brake lever is engaged (if applicable), the PTO (power take-off) is disengaged, and for riding mowers, that you are seated correctly. A faulty or bypassed safety switch will prevent the engine from cranking or firing.
Unraveling starting dilemmas
When your Bolens mower cranks but won’t start, or simply clicks, the problem typically lies within one of three critical systems: fuel, ignition, or compression. A systematic approach to these areas is key to pinpointing the exact cause.
Fuel system inspection:
- Fuel flow: Disconnect the fuel line from the carburetor (place a container underneath to catch fuel). If fuel flows freely, your tank, fuel lines, and fuel filter (if present) are likely clear. If not, check for clogs in the fuel filter, kinks in the line, or a clogged fuel tank vent.
- Carburetor issues: The most common fuel-related starting problem is a clogged carburetor. Residue from old fuel can block jets and passages. Try spraying a small amount of carburetor cleaner into the air intake while attempting to start. If it sputters or briefly fires, it confirms a fuel delivery issue. A full carburetor cleaning or rebuild might be necessary.
Ignition system check:
- Spark plug: Remove the spark plug. It should be clean and dry. If it’s fouled with carbon deposits or wet with fuel, clean it with a wire brush or replace it. Check the gap against your owner’s manual specifications. Reconnect the spark plug wire, ground the plug against a metal part of the engine, and try to crank the engine. A strong, blue spark indicates a healthy ignition system at the plug. (Always hold the spark plug with insulated pliers or heavy gloves to avoid shock).
- Ignition coil: If there’s no spark, and the plug and wire are good, the ignition coil might be failing. This is a more advanced diagnosis, often requiring a multimeter to test resistance or replacement for confirmation.
Compression assessment:
While less common for sudden no-start issues, low compression can prevent an engine from firing. You can get a rough idea by pulling the starter cord. If it feels unusually easy to pull with little resistance, you might have low compression. This could indicate worn piston rings, valves, or a blown head gasket, requiring professional repair.
Diagnosing performance and running issues
A Bolens mower that starts but runs rough, stalls, loses power, or smokes indicates problems that often relate to fuel-air mixture, engine timing, or exhaust. These issues affect overall engine efficiency and can stem from several areas.
- Air filter blockage: Revisit the air filter. Even if it looked okay for starting, a partially restricted filter can cause bogging down under load or excessive black smoke (too rich a mixture).
- Carburetor adjustment: If the mower runs rough, surges, or stalls, the carburetor might be out of adjustment or partially clogged. Lean mixtures (too much air) can cause surging and overheating, while rich mixtures (too much fuel) cause black smoke and poor power. For mowers with adjustable carburetors, consult your manual for proper settings. Often, a professional cleaning is the best remedy for internal blockages.
- Spark plug condition: A worn or fouled spark plug can cause misfires, leading to rough running and power loss. Inspect and replace if necessary.
- Valve clearance: Incorrect valve clearance can cause poor compression, affecting engine performance. This is a more intricate adjustment and usually requires special tools and mechanical knowledge.
- Muffler or exhaust obstruction: A clogged muffler or exhaust port can restrict the engine’s ability to expel gases, leading to reduced power and overheating. Remove the muffler and inspect for blockages.
- Blade issues: While not directly engine-related, a dull, bent, or unbalanced blade can cause excessive vibration, put extra strain on the engine, and result in an uneven cut. Sharpen or replace blades as needed.
Here’s a quick reference for common running problems:
| Symptom | Potential Cause(s) | Action |
|---|---|---|
| Engine runs rough/surges | Dirty carburetor, old fuel, clogged air filter | Clean carburetor, drain/refill fuel, replace air filter |
| Loss of power under load | Clogged air filter, dull blade, dirty carburetor, low compression | Replace air filter, sharpen blade, clean carburetor, check compression |
| Black smoke from exhaust | Too rich fuel mixture, clogged air filter | Check carburetor, replace air filter |
| White/blue smoke from exhaust | Burning oil (worn rings/valves), head gasket issue | Check oil level, consult mechanic |
| Engine stalls frequently | Dirty carburetor, clogged fuel filter, faulty safety switch | Clean carburetor, replace fuel filter, test safety switches |
Electrical system and safety interlock pitfalls
If your Bolens mower exhibits no signs of life, meaning no cranking or clicking when you try to start it, the problem often points to the electrical system or the safety interlocks. These components are designed to protect both the operator and the machine, and a fault in any one of them can prevent operation.
Battery and charging system:
- Battery charge: For electric start models, a dead or weak battery is a common culprit. Check the battery terminals for corrosion and clean them if necessary. Test the battery voltage with a multimeter; it should read around 12.6 volts when fully charged. If low, try charging it. If it doesn’t hold a charge, replacement is likely needed.
- Starter solenoid: If you hear a single click but no crank, the starter solenoid might be faulty. This component acts as a switch between the battery and the starter motor. You can often test it by carefully jumping the two large terminals on the solenoid (with the mower in neutral and spark plug disconnected) to see if the starter motor engages.
- Starter motor: If the battery is good and the solenoid clicks but the engine doesn’t turn over, the starter motor itself could be bad. This usually requires removal and testing or replacement.
- Charging system (for riding mowers): If your battery keeps dying, the alternator or stator might not be recharging it. This is a more complex diagnostic involving testing output voltage while the engine is running.
Safety interlock switches:
Modern Bolens mowers are equipped with several safety switches that must all be engaged (or disengaged, depending on their function) for the engine to start or run. These include:
- Seat switch: On riding mowers, this prevents the engine from running if no one is in the seat, especially if the PTO is engaged.
- PTO switch: Ensures the blades are disengaged before starting or if the operator leaves the seat.
- Brake/clutch switch: Requires the brake or clutch pedal to be fully depressed for starting.
A faulty or disconnected safety switch can mimic a dead battery or starter problem. Visually inspect all wiring connections to these switches for damage or corrosion. Testing them usually involves a multimeter to check for continuity when the switch is engaged and disengaged. Be aware that attempting to bypass these switches is extremely dangerous and not recommended.
Troubleshooting your Bolens lawn mower doesn’t have to be an overwhelming task. By systematically working through the possible culprits, from the simplest checks to more intricate system diagnostics, you can often identify and resolve issues yourself. We’ve explored the crucial steps, starting with vital safety precautions and initial inspections, then moving into the nuances of starting problems related to fuel, ignition, and compression. We also delved into common running and performance issues, highlighting the importance of air filters, carburetor cleanliness, and spark plug health. Finally, we tackled electrical system failures and the ever-important role of safety interlock switches, which often prevent any sign of life from your mower. Remember, patience and a logical approach are your best tools. Always refer to your Bolens owner’s manual for specific models, and don’t hesitate to seek professional help for complex repairs. With these insights, you’re well-equipped to keep your Bolens running smoothly for years to come.