I just bought a john deere 310c and it started white smoking and smelling like diesel pretty bad. Runs a little rough as well smells like raw fuel. Not sure where to start
With the engine off, loosen the injector lines at the injectors, hold one wrench on the injector side of the fittings so you don't bend anything on the injector, they're fragile. Then tighten them up comfortably, start it, and loosen them again, only one at a time. You'll probably notice one where the rough running doesn't change much, and hopefully the white smoke goes way down, that's your bad cylinder. When you loosen a line on the injector on the good cylinder is should start running much rougher, and improve as soon as you tighten the nut. Once you've identified the bad cylinder, you need to remove that injector which might be tough. There's a slide hammer remover thing, or you can grab them with a vice grips and rotate until you get them loose enough to pry out. Once out, thepumpguy would tell you to rotate the line (don't bend) or the injector to hook up the injector facing out to check the spray pattern, or just put a new one in, if that doesn't fix it, then do a compression test on that cylinder.