The nozzle-and-holder assembly in a vehicle’s fuel injection system comprises a nozzle holder and a nozzle, with a compression spring inside the holder acting on the nozzle needle. This assembly plays a critical role in precisely controlling fuel delivery to the engine cylinders. The compression spring maintains the nozzle needle in a closed position until fuel pressure reaches the required level. At that point, the spring force is overcome, prompting the nozzle needle to open and inject fuel into the combustion chamber. This precise control enables efficient fuel atomization, optimal combustion, and overall engine performance.