Abstract: A test apparatus and method is disclosed for a fuel pump mounted on and driven by an engine, the speed of which is controlled by the pressure of fuel supplied thereto wherein the engine continues to be supplied with fuel from the fuel pump during the test. A fluid circuit is provided which is designed to supply fuel to the engine under controlled pressure to permit the engine speed to be controlled independently of the engine throttle position and to permit the flow rate of the fuel to be adjusted to a predetermined value at which the output pressure of the fuel pump may be measured for calibration purposes. The fluid circuitry and necessary measurement circuitry may be mounted within a small, portable housing to allow for field testing of a fuel pump.