Signs of bad spark plug on snow blower engines can be confused with several other issues all of which have similar symptoms. For example if your snow blower engine will not start it could be because there is no gasoline in the tank (don’t smirk this happens a lot). Also bad gas that has clogged the filters and / or carb. A bad spark plug or no spark at all getting to the spark plug. The easiest way to trouble shoot these problems is to check the easy things first.
Eliminate them and move onto the more difficult areas. For example, always check that you have gas in the gas tank and if there is a shut off cock for the gasoline, that it is open! Many people shut this off in the spring and then forget that they did that when it comes to firing the snow blower up in the fall.
The next easiest thing to check is the spark plug. Remove the wire connected to the plug and hold the metal end of the wire within 1/16th of an inch to the end of the spark plug. Have some one slowly pull the starter chord. You should see a spark. Be careful not to touch anything metal connected to the machine to avoid receiving a shock. It will not hurt you but it will give you a bit of a surprise.
Next remove the plug, clean it and re gap it to the specification in your manual. If the spark plug is badly corroded or cannot be cleaned properly, replace it with a new one. Make sure you also set the gap on this plug as well. If your engine is still running rough or not at all you will have to search for other solutions.
At this point you know you have gas in the tank. The shuttle cock is open so gas can get to the carb. You know there is spark getting to the spark plug and you have either cleaned the plug or replaced it. What’s next? Turn the engine over a few times, remove the spark plug and check for gasoline on the plug. If the plug is wet, and you can smell gasoline, then gas is getting into the engine. You will need to recheck that it is gaped properly and that the spark plug is actually receiving a jolt of electricity. If it is dry then gas is not getting into the engine and you will need to recheck and / or clean the carb and gas tank.