A plunger metering pump displaces chemical using a precision-machined plunger moving through a cylinder bore, driven by a motor through a crankshaft or cam mechanism, generating higher pressures and tighter accuracy than a diaphragm pump can typically achieve at the same flow rate. Because the plunger moves in direct contact with the process fluid, sealed by packing rather than isolated behind a diaphragm, this design handles the high pressure injection points common in oil and gas production, deep well injection, and other applications where discharge pressure requirements exceed what diaphragm technology comfortably supports. Packing wear is the main maintenance consideration with this design, and is managed through adjustable packing glands and periodic replacement scheduled around chemical compatibility and operating pressure.