Cleanliness is a prerequisite for all work on a diesel engine. Be sure to clean the union nuts of the pressure pipe before loosening them. The high pressure fuel pump cannot be disassembled or repaired. and if it fails, it is replaced. To adjust the high pressure fuel pump, special tools and accessories are required and should be done in a workshop. Diesel engines operate with either direct or indirect injection, that is, when fuel is injected into a prechamber in the cylinder head, which is connected to the combustion chamber itself. The combustion process begins in the prechamber and, under the resulting pressure, fuel particles are drawn into the combustion chamber, where they» their complete combustion occurs.