How To Troubleshoot Your Lawn Mower
Carburetors with primers represent a large majority of lawnmower and small engines today. They have primers to push or force air in the carburetor and in turn force gas through the center jet to make starting easier. Look to see if the primer is pumping gas in to the engine.
Things to check for if the primer is not working. This applies to several different types of engines. Check for holes or tears if you have a carburetor that has a diaphragm. (A diaphragm is a gas pump located in carburetors that have the gas tank and carburetors assembled together.) Replace the diaphragm if the diaphragm has a hole or has hardened or slightly slid over to one side, or if the engine will not run correctly and is skipping, not priming, or will not run at all.
Float Type Carburetor
With a float type carburetor, the bowl gasket Will not be sealed properly and air will leak past the bowl gasket and will not prime.
Air Assembly Primer
If you have a air assembly primer box where the air filter box is connected to carburetor, your gasket will not be sealing correctly.
If there is a tear or a hole in the gasket, air will leak past it and will not force air in the carburetor which will not force gas through the center jet. Also your air assembly box Will have a crack and will be warped because it was over tightened. If so, replace it.