Vacuum Pump Operation:
Diesel applications pretty much have a consistent flow of air into the engine due to a lack of restriction in the intake area. Therefore, they do not create any vacuum of their own. The addition of a separate gear driven or belt driven vacuum pump allows vacuum driven accessories to be installed to perform various tasks within the vehicle. The gear driven version is usually driven by the same gear assembly that drives the sump mounted oil pump providing lubrication for the entire engine. There are a small number of gasoline engines that use these pumps to supply supplemental vacuum as a booster to operate more accessories or perform more tasks.