Diesel basics
Yours is a tough question in that there are many problems that cna be encountered on a diesel and ther are many degrees of idiocy. We presently have two books on the shelf pertaining to diesel engines. The first, by Don Seddon is called Diesel Troubleshooter. It is quite basic and covers many of the problems that you might encounter. The other, by Nigel Calder, called Marine Diesel Engines, is more comprehensive. Both start with the theory of operation of a Diesel Engine, which I feel is essential to understanding anything about diesels. Each diesel has its own peculiarities. Once you have the basics, you will better understand what is in the service manual for your engine. When in doubt, consult (or use) a good mechanic.