This document provides an overview of reciprocating engine fuel metering systems. It discusses the properties of reciprocating engine fuels and color coding used to identify different types of aviation fuel. It also describes the operation and components of typical gravity-fed and pressure-fed fuel systems, including fuel tanks, lines, valves, filters, gauges, pumps and primers. The key requirements for fuel systems are outlined, noting they must supply the proper amount of fuel to the engine under all operating conditions.