One of the most common diesel complaints is a hard to start or will not start situation.
Every detail is important when trying to diagnose such a problem.
One should determine if engine temperature has anything to do with the problem, ambient temperature should also be considered. Close attention should be paid to the cranking R.P.M. as well as the glow plug system. Starting problems are often electrical related since cranking R.P.M. and the glow plug system are very critical to getting the fuel to burn. Batteries and the starter should also be a consideration if cranking R.P.M. seems slow. Once the electrical system is ruled out, air entering the system should be considered, especially if the engine cranks, dies and is then hard to restart.