SECTION A (40 MARKS) Answer ALL questions in this section.

During the operation of a diesel electronic fuel injection system, the "Pressure Drop Phase" refers to the rapid decrease in fuel pressure within the injector assembly after the main injection event. This drop in pressure is crucial for quickly closing the injector nozzle, preventing secondary injection or dribbling of fuel, and ensuring precise control over the amount of fuel injected into the combustion chamber. It helps to achieve clean combustion and reduce emissions.