The lawn mower small engine often has a separate model number. Use the small engine model number for a complete list of symptoms and parts. Watch our model # lookup video for help finding the model number.
The 2 most common part(s) or condition(s) which cause the symptom Lawn mower won't start are listed below starting with the most likely. Check or test each item and watch any available videos.
If the lawn mower does not start, the carburetor might be clogged or have old or bad fuel in the float bowl. If old or bad fuel was left in the lawn mower for a long time some of the volatile ingredients may have evaporated, leaving a thicker, stickier product that is more like varnish or shellac. This sticky fuel can clog up the small jets and ports in the carburetor and it can be difficult to burn making it hard to start the engine. The only solution is to drain the old fuel from the float bowl and thoroughly clean the carburetor with carburetor cleaner. If that isn't effective, replace the entire carburetor.
RepairClinic Item # 1826743
If the lawn mower does not start the safety switch might be defective or it might be sensing a problem with the lawn mower, preventing the engine from starting. Normally the safety switches can be checked for continuity with an Ohm meter or continuity checker. If it has continuity it's OK. If not, replace it.