I have a 7.3 that's running rough. Started it the other day it ran alright but started blowing white smoke. Bought a oil and fuel additive i was going to run through it. Came a few days later, it stated up and was real loud and sounding like it was loping. It blew a good amount of white smoke, but it just smelt like real heavy diesel. Now i can only turn it over and it won't start. Any help

 

Need more information? What year truck type etc.. Did you get it hot? Did you checjk the valve cover harnesses? Is one side of the motor, exhaust manifold, hotter then the other?

 

Sounds like a stuck open injector. Run a contribution test with a comparable scanner.