i have a walker mower that will just sut off. for some reason the battery keeps goin dead. i had it checked and supposly its good. i can jump the mower off and it will run for about 5 min some times less, and then just cut off. usually i can jump it back off and it will run for a bit and die again. but today it ran for about 5 min and died and now it wont start. it wont even turn the starter over. i hooked the jumper cables to it and it wont do anything. with the cables hooked up i can make the starter spin using a screwdriver to jump the selenoid. but when i turn the key with the cables hooked up it does nothing. anyone got an idea?