Most mowers are built to be easy to operate and maintain, but you’re bound to have problems with even with the best equipment. For walk-behind mowers, at one time or another, you’ll find that the engine just doesn’t want to start. Fortunately, there are a few common causes for this that are easy to fix.
Most small engines use a splash lubrication system with the crankshaft pushing the oil around inside the motor’s bottom end. At temperatures under 50°F (10°C), the oil inside the engine is thicker, which means it takes more effort to spin the crankshaft through it. Usually, it just takes a couple of extra pulls to get the engine running, but if you’re still having difficulty, roll the mower outside so it can warm up in the sun.
If you regularly use your mower at low temperatures, switch to a synthetic oil, which doesn’t thicken as much in the cold.
A clogged filter can make drawing air into the engine so difficult that it can reduce power or stall the engine. Check the air filter and clean out any dirt and debris build-up. The filter will be in a plastic housing located either on the top or side of the engine.
To clean a paper filter element, simply tap it against a hard surface. Don’t try to wipe away contaminants: this can force them into the filter, restricting airflow.
To clean a foam filter, wash it in a mild detergent and water. Once it’s completely dry, soak the filter in clean engine oil and squeeze out any excess.
If the filter is dirty or damaged, it should be replaced.
Check the Controls
There are a number of conditions that must be met for the engine to start — most of these are for safety reasons. Your owner’s manual and engine manual will go into more detail for your specific mower, but there are a few common things to check:
- Is there a bail on the handle that has to be closed? Is the cable running between the bail and the engine still in place?
- Is there a PTO switch for the blades? Is it off?
- Does the engine have a manual choke that needs to be closed?
- Is there a separate throttle? Is it set to “fast” or “choke?”
- Is there a priming bulb that needs to be pumped to draw fuel into the carburetor?
Have a self-propelled mower? Some models have a second bail to engage the propulsion system. This bail needs to be left open for the engine to start.
Is there fuel in the tank, but the engine doesn’t want to start? Modern fuel goes stale quickly, which makes it harder for the engine to burn. If the fuel is more than 30 days old, it needs to be replaced. If you need to store fuel for over a month, add a fuel treatment.
Your mower’s engine can’t run on fuel blends with more than 10% ethanol, like E15 and E85.
Check the spark plug. Both the plug and wire need to be clean, and the wire needs to be securely snapped to the end of the plug. If the electrode is worn, there’s damage to the insulator, or the plug is fouled, the plug needs to be replaced. The end of the spark plug should be wet if you’ve tried to start the engine: this wetness is fuel from the carburetor. If it’s still dry, you probably have an intake or carburetor problem.
On models with an electric start, make sure the battery is fully charged. Plug the mower into the charger and check the charging light. If it’s yellow or red, the battery still needs time to charge. Bringing the battery up to full charge can take a full day.
Where to Buy Parts and Accessories for Your Mower
Whether you need a new filter, a spark plug, or a new charger, you can get it from Shank’s Lawn Equipment. No matter where you are in the U.S. or Canada, Shank’s can ship the parts you need to keep your mower running. Or, you can take a look at all of the 2016 models in our updated brochures.
Having problems with your mower and live in South Central Pennsylvania? Stop by our shop, located at 4900 Molly Pitcher Highway in Chambersburg, just off route 11. To get there from I-81, take Exit 10 to Marion.