Why Will My MTD Lawnmower Not Start?

Fuel System

• The fuel originates in the fuel tank and travels up to the carburetor via a fuel hose. After mixing with air in the carburetor, fuel gets sent off to the cylinder for ignition. However, if the supply of fuel drops, even slightly, the balance in the engine will be wrong, and it may not start. Fuel imbalances cause most starting problems, and the entire fuel system should be checked to locate any possible points of pressure loss or fuel blockage. Common problem areas include the fuel tank, fuel cap, fuel filter, fuel hoses and carburetor inlet jets.

Insufficient Air Supply

• Once the fuel hits the carburetor, it gets mixed with air and delivered to the cylinder. However, for the fuel to ignite properly, it needs to be mixed with a precise amount of air. Like the fuel supply, if this air supply drops, even a little, the engine may shut down and not start. Pull the air filter pad out of the air filter box and wash it in soapy water. Clean out the muffler and spark arrestor screen with a brush.

Insufficient Spark

• When the fuel and air combination hits the cylinder, it gets ignited, further powering the piston's up and down stroke and the crankcase's movement. However, this spark needs to be delivered at the right time with the right amount of voltage. Like the fuel and air systems, if the spark is off, even slightly, the engine will stop firing. Turn the ignition switch off. Pull the spark plug from the cylinder; and if the tip looks fouled, replace the plug. Take your MTD mower into a mechanic to repair the ignition system if you suspect the problem lies there.

Low Oil

• For all of these systems to continue to function normally, the engine needs to stay cool, and the piston and crankcase need to stay lubricated. If the lubricating system dries out, the piston and crankcase may heat up to the point they blow out the seals and valves or degrade the bore enough to cause movement problems. When this happens, the engine will not only start, it may never start again. Check the supply of oil in the crankcase; and if it hasn't been changed within more than 25 operational hours, change it.