Broken Primer on a Lawn Mower

Empty Fuel Tank

• The fuel tank must be emptied before you access the primer function on a lawnmower. Either run the mower -- if you can start it -- until it starves of fuel or open the tank and drain the fuel into an approved fuel container. When tilting the engine over, always drain with the carburetor up to prevent fuel and oil from spilling into the carburetor. Clean up any spilled fuel with a rag, especially if it spilled near the carburetor or the combustion chamber.

Access the Primer

• On many lawnmowers, the primer bulb sits on the side or the top of the carburetor. Other models use a remote primer, with a fuel hose connecting the primer to the carburetor and the fuel tank. To gain access to this, the air filter box must be removed on many mower models. Use a flat screwdriver to remove the air filter box from the side of the engine.

Remove the Bulb

• The bulb attaches to either the carburetor or the engine through a mounting tab. This tab often has two screws mounted on either side. These screws generally take a Phillips screwdriver and vary in size. Loosen and remove these screws. Pull the primer, connected to the tab, out of the engine. Pry the primer bulb out of the tab if it's still attached. Replace the primer if it's ripped, cracked or damaged.

Complications

• After replacing the primer bulb, check the priming function on the lawnmower again. If the bulb still doesn't inflate, pulling in enough fuel for the carburetor and engine to start, the entire fuel system may need servicing. Any point throughout the fuel system can interrupt the flow of fuel. Dirt, grass clippings and fuel impurities can jam the system. In this case, the fuel system must be disassembled and cleaned, and the fuel filter and both fuel hoses should be replaced.