I got the mower up and running yesterday and I just started with the blades. I was going down a hill, that i have done the past few years. It sounded like I ran something over but I didnt see anything and then my mower died. It won't start but it goes chug chug chug then sounds like the engine scrapss..I changed the spark plug, oil filer, air filter and it still won't b e anything. Could it be a fuel filter or fuel line?... Any advice, I tried to look at the blades nothing seems to be holding the blades back.. Its a 2009 Craftsman 19.5 hp gold riding lawn mower. Never had any issues with it till now.