Broke down and then won't start is a bit different to plain 'won't start'.
So many possibilities that without ruling something out you'll never get to the bottom of it.
Other than a code read starting with the basics such as ensuring air free fuel is being drawn up from the tank. You could bypass the fuel filter and allow the engine to suck up some clean diesel from a clean container along the lines of this epic video (use an in-line filter to protect your system).
https://www.youtube.com/watch?v=xYsXHC2-PSw
Or just fit a section of clear fuel pipe so you can see if air free fuel is being drawn up. A few small bubbles shouldn't be an issue.