How do i fix my 1994 MTD?

First off it will not start on its own, it has to be jumped, when started with a jump it blows white smoke out of muffler along with gas and or oil but after it runs for awhile it runs ok, when shut off it will not start again, unless jumped again. I have changed spark plug, oil, fuel filter, and also new battery, it also gets gas and or oil blowing out of the breather, almost as if its not getting enough air