PURPOSE: To provide a system for determining the fuel injection characteristics of a fuel injection pump with an electric means, and which system has such a construction that a differential transformer output can be obtained according to the displacement of the valve member of an outlet valve, with the converted electric output used for various measurements and analyses.

CONSTITUTION: In a system, in which a plunger 3 is mounted on a tappet 2 engaged with a cam 1, and also in which the plunger 3 is moved along a plunger barrel 4 coupled to an outlet valve 5, an outlet valve retainer 6 coupled to an outlet valve 5 is made of a non-magnetic material and provided on a differential transformer bobbin, and a differential transformer coil 7 consisting of primary and secondary windings wound one over another is provided on the outlet valve retainer 6. A valve member of the outlet valve 5 is made of a high magnetic permeability material and provided on a differential transformer coil. With this construction, the differential transformer output can be obtained according to the displacement of the valve member of the output valve 5, and the output thus obtained through conversion can be used for various measurements and analyses.