To prime a self-contained dispenser pump, you squirt:

Priming a self-contained dispenser pump is a critical step in ensuring that the pump operates effectively, particularly in getting the pump's internal components ready to start moving liquid. In this context, the correct choice revolves around the appropriate substance used for priming.

Using heavy lubricating oil in the strainer cavity serves to create a barrier that helps in forming a better seal, thus enabling the pump to function optimally when it begins to draw the product. Heavy lubricating oil can enhance the lubrication of the internal components, decreasing initial friction when the pump starts, which can be vital for maintaining the longevity and efficiency of the pump mechanism. This helps ensure that any cavitation (which can occur if the pump isn't sufficiently primed) is minimized.

In contrast, squirting other substances, such as a lighter oil or product itself, may not provide the same level of initial sealing and lubrication needed for reliable pump operation. In addition, putting product in areas where it doesn't belong, like the gear pump cavity or strainer cavity, could lead to issues like improper function or even damage to the pump over time. Therefore, heavy lubricating oil is the correct choice for adequately priming a self-contained dispenser pump.