Small Engine No Start Diagnosis (see description for written steps) 

This is a step by step video of the process I use at my shop to diagnose a small engine that won’t start. Here’s the basic run down; You need these things for an engine to run AIR, FUEL, SPARK, and COMPRESSION. Here’s how you find out which one you’re missing…. 1)Check the oil. Make sure it’s not low or contaminated with fuel. 2)Check to make sure the engine kill switch cable works 3) Spray some starter fluid in the carb, if it starts for a second, you have a fuel delivery (carburetor) issue. 4) Check for spark. If no spark, make sure your plug is good and check the ground wire to your coil. If it is broken or chaffed, repair and test again. If still no spark, replace ignition coil. 5). If you have spark, and still no start with starter fluid, test compression. 6) If compression is low, removing the head to check the head gasket, valves, piston and piston wall for damage or scoring.
Steps for an electric start mower are similar, the main difference is that if you get no spark, you’d also need to check the ignition to make sure it’s working properly and not grounding out the coil. The easiest way to do this is to temporarily remove the ground wire from the magneto (ignition coil) itself and attempt to start. If you still have no spark, you need to replace the ignition coil. If you get spark, either the ignition switch is bad or the ground wire from the ignition switch to the ignition coil is grounding out somewhere.