Well, your fuel system is contaminated. Maybe it was the common failure point of the CP4 injection pump, DEF was introduced to your fuel tank or that kid down the street that keeps riding his bike through your flower beds decided to sugar your tank for telling his mom on him. Having to replace the entire fuel system in your 2011-2016 LML Duramax is immensely expensive. Our friends at XDP have gathered a kit together to try to cut some of the parts costs down so your truck doesn't have to be mechanically totaled out.