Abstract: This invention relates to a positive displacement adjustable volume pumping and dispensing system used to supply measured amounts of viscous material. The system includes a pneumatically or hydraulically driven submersible adjustable volume piston-type pump, and a combination two-section pinch-off aspirator valve that is connected to the pump. The pinch-off section of the valve is used to dispense the metered amount of fluid to the aspirator section of the valve and the aspirator section of the valve prevents drip from the nozzle after the material is dispensed as well as aids in advancing the material to a dispensing nozzle.