Causes for a Murray Lawn Mower That Won't Prime

Gas

• Check your gas levels. The primer’s function is to inject gas into the carburetor for the ignition function. The injected gas creates vapors, which mixes with air. The mixture is then ignited by the spark plug. If there isn’t enough gas in your tank, there may not be enough gas to load into the primer.

Primer Bulb

• The primer bulb uses air pressure to push gas from the gas tank into the carburetor. It is located next to the gas cap on the 90000 and 100000 Murray mower models. When you depress the bulb, it forces gas into a small primer tube. This usually takes a few presses to load enough gas. Thus, a broken primer bulb can prevent gas from entering the primer tube. Look for holes or tears in the bulb, which can reduce the necessary air pressure needed for pumping.

Carburetor Diaphragm

• Some carburetors use a diaphragm pump, like on Murray mowers with the Briggs and Stratton model 10T800. The diaphragm pushes gas through the carburetor when the mower’s throttle is pulled. The diaphragm also has a gasket that provides a tight seal so that none of the primed gas leaks out. If the diaphragm has a tear in it, it is possible that primed gas is not reaching the carburetor. Diaphragms can also get hardened or become off-set, also preventing gas from reaching the chamber.

Float valve

• Other mowers have carburetors that inject gas into a float chamber by using a float control valve. The float control valve drops to the primer’s level when there is no gas in the float chamber. If the float control valve is broken, it won’t reach the primer’s level to allow gas in. Float valves that hold gas for a long time can also create sediments and residues, which can clog the connection to the primer. The valve also has a gasket that will leak air if torn.