Outdoor Power Equipment and Small Engines - HELP Murray won't run decent

We have a 22 inch 4.5 B & S Murray push mower that worked fine until recently. The mower sits at a lot and is used to cut the lawn. It worked fine until we just tried to cut the lawn after a couple weeks of sitting . It isn't running correctly, speeds up, slows down, spits and sputters, and is missing. We've checked it all over and can't find anything wrong. We replaced the spark plug, (it was very black at the tip) added more fresh gas, checked the air cleaner, and also tried to run it without the gas cap on, as was a suggestion somewhere else in the forum.(didn't help in the performance any) Any other suggestions anyone? Any help would be appreciated. This mower is only about a year old. It is stored outside with some limited shelter from the elements. Help me please. :(

Hello mowingmomma!

It sounds to me like you need to replace the diaphragm. It is between the carb and the gas tank. Less than $5.00. Also, check for water in the bottom of the tank and drain/dry if necessary.

mowingmomma
With a spark plug being black like you're describing sounds to me like a very rich (fuel) running condition. Like Cheese said, it sounds like a carb issue. I'm not sure whether you have a diaphragm or float bowl carb on your unit but the carb is definately where to start checking. Because if it sits outside that isn't the greatest thing for it, possible moisture buildup in the tank, maybe the ignition could be getting rust on the legs and that can cause running problems.
Start with the carb and let us know what happens.

snoman

We will be looking into those areas over the weekend, and I'll get back with you on the verdict. At least you gave us some things to check out. Thanks for your input and help. :)