This is for any novice such as myself to learn from so you won't go threw what I had to learn the hard way.
I had a problem with a md7a not starting and thought I finally had it licked because it ran a couple weeks ago again for a couple days and then stopped again last week. Thought it was a spin on fuel filter but it was not. I would bleed it and bleed it but it would blow white smoke and get fuel but never start. What had happened "using all my newbie to diesels infinite wisdom NOT" was when all this started to begin with, I had found a bolt that had broke off on the return line right where it goes into my fine fuel filter and had replaced it. What my stupid self did not know is I replaced it with a regular bolt not a banjo bolt. I finally put all this info together tonight and will be replacing the regular bolt with a banjo bolt tomorrow and I am optimistic "hopefully not too much" that this thing will start again since I finally learned that a banjo bolt will allow fluid to flow but a regular bolt there will not. I guess when it started and ran for a little while that bolt that was in there was a little loose or enough fuel was out of the return line to just get it to start and run for a little while. Hey this is the first diesel I have ever owned, I am a computer tech not a mechanic so this has been a education for me. Hope this helps someone and even if you know the difference between the bolts it is definately a place for you to start troubleshooting if you ever have the same symptoms where no matter how much you bleed it the thing will just not start. I did replace all lines from the tank all the way to the lift pump so no leaks now if there were ever any to begin with since I think it was the bolt on the return line the whole time.