What is the primary function of fuel units (oil pumps)?

The primary function of fuel units, or oil pumps, is to draw oil from the tank to the burner. They are designed to perform this critical task efficiently to ensure that fuel flows continuously to the burner for combustion. This flow is necessary for maintaining the fuel-to-air ratio required for optimal burner operation, which directly impacts the efficiency and effectiveness of the heating process.

In the context of the other options, storing oil for future use is not a function of the pump itself, as that is the role of the storage tank. Heating oil before burning could be a function of other components in the system, such as a heat exchanger, rather than the pump. Finally, purifying the oil before use is the role of filtration systems, which ensure that impurities are removed before the oil reaches the burner. Thus, the oil pump's primary function is clearly to facilitate the movement of fuel from the tank to the burner, making the correct choice the most relevant to the operation of heating systems.