My Murray Lawn Mower Bulb Primer Is Not Working

Blocked Fuel Flow

• For the primer bulb to work properly, it needs to use suction in the airtight fuel system to draw fuel out of the tank and up to the carburetor. If the fuel can't leave the tank, the suction power of the bulb may not be sufficient to pull the fuel all the way through. Clogs in the fuel tank, the fuel filter or the fuel hoses may cause a backup in the system. Dirt, grass clippings or impurities in the fuel can stick to the tank, filter or hoses and block the system.

Fuel Hose Problems

• If the fuel hoses don't maintain an airtight seal with the fuel tank and the carburetor, the primer bulb can't deliver enough suction force to pull fuel into the carburetor. Fuel hoses will degrade after several seasons and will get brittle enough to crack slightly. These cracks can let enough air into the system to stop the fuel from flowing. Replace any worn or cracked fuel hoses and change the fuel hoses at least every other season.

Primer Bulb Repair

• The primer bulb on a Murray lawn mower either sits in the middle of the purge line or directly on the carburetor. The primer bulb also needs to maintain an airtight seal with the hoses or the engine to use the force of the suction to draw up a sufficient amount of fuel. The fuel can also degrade the primer bulb, making it brittle enough to crack slightly when it gets depressed repeatedly. Replace any cracked or worn out primer bulbs.

More Serious Complications

• Issues with the primer bulb can allude to more serious complications, usually within the engine's interior. For the carburetor's diaphragm-style fuel pump to pull enough fuel in, it needs to use the vacuum pressure created through the pulsing of the crankcase. As the crankshaft spins inside the crankcase, it generates the vacuum needed to squeeze the diaphragm, which uses that suction to draw fuel into the carburetor. If the primer bulb still won't primer after making the above repairs, pressure test the carburetor and crankcase for any air leaks.