Abstract: The volumetric output of fuel injectors is rapidly and accurately measured y accumulating in first and second counters respectively, a count of pulses generated as a function of the strokes made by the injector, and a count of pulses generated by an optical encoder attached to the piston of a positive displacement flow meter through which the output of the injector is directed. When the first counter reaches a count representative of a preset number of injector strokes, the accumulated count in the second counter representative of injector output for the preset number of strokes is stored and displayed continuously while the counters are reset and the test cycle is automatically repeated. The direction of movement of the reciprocating piston of the positive displacement flow meter is automatically reversed by the control system as either end of travel is reached through coordinated operation of a pair of solenoid valves.