Your lawn mower can be a real pain at times when it won’t start or will run for only a few seconds. You pull it out, turn the key or pull the starter rope and nothing. Well, instead of breaking out the old “sledgehammer”, let’s take a look at some things you can do to try and get that lawn mower back up and running quickly.
If you have a self-propelled lawn mower or push mower, the first thing you want to do is check for spark and fuel. Start off by removing the spark plug and see if there is any fuel on the end of the plug. Next, attach a spark tester to it. If you don’t have a spark tester, you can leave the spark plug attached to the spark plug wire and lay the spark plug on the metal part of the engine and either video tape the spark or use a mirror in front of the lawn mower to help visually see any spark.
If you have spark and are not getting any fuel, then a carburetor problem is the likely culprit. If you have no spark but are getting fuel, then your ignition magneto is bad or something is grounding out the kill wire. The kill wire is the black wire that connects to the spade connector on the ignition magneto and is routed to the kill switch that is activated when you release the safety bail.
If your lawn mower has sat over the winter, the fuel is bad and will need to be drained and new fuel put in the tank. The carburetor may also be gummed up by that old fuel so it may need cleaned as well.
Riding lawn mowers are basically the same to troubleshoot. But with a riding lawn mower, be sure that the battery is completely charged and that the main fuse is good and not blown. If you turn the key over and nothing happens, you either have a battery issue, a bad key switch or wiring, a starter solenoid that is bad, a bad negative cable ground or a safety switch that is not working.
If your lawn mower will still not start, a VERY SMALL amount of starting fluid can be sprayed into the carburetor venturi after the air filter has been removed. If the engine does fire, then you know for sure that you have a fuel problem and there is none going through the ports in the carburetor.
Just remember, an internal combustion engine needs fuel/air mixture, spark and compression to work properly. If you have all of those and the engine timing is correct (you didn’t hit something with the lawn mower blade on push and self-propelleds), your engine should run.
Hopefully this gets you pointed in the right direction to get your lawn mower will not start troubleshooting issue resolved quickly.