I've got a 2012 L2800HST, And it blows a ton of black smoke when running, even at idle. It's also getting fuel into the oil. If it runs for more than a few minutes it also wont shut off, i have to pinch off the fuel line coming out of the filter and it eventually dies. i've replaced all 3 injectors, so i know they're good. i've bench checked the shut off seloniod, and it seems good. I'm pretty mechanically inclined, but not super well versed in diesels. I know black smoke is usually too much fuel? Any ideas what to look at next?