The primer vane is located in the primer housing, which is attached to the side of the pump. The primer vane is driven by the pump shaft and rotates in a chamber filled with oil. As the vane rotates, it creates a vacuum that draws oil from the reservoir into the pump.
Once the pump is primed, the primer vane is no longer needed and it stops rotating. The oil that is used to prime the pump is then circulated throughout the pump and its components, lubricating and cooling them.