Diagnostic system for fuel injected engines

Abstract

An electronic timing system for fuel-injected engines is disclosed in which a direct readout is provided for measuring the time relationship between fuel injection and the achievement of the top dead center (TDC) condition in a preselected cylinder of a diesel engine. A piezoelectric transducer coupled to the fuel-injection system provides a pulse upon the injection of fuel into a feed line for the selected cylinder. This pulse is detected in a noise blocking, variable threshold, amplifying circuit and initiates a timing pulse, the width of which constitutes a delay period after which a strobe light is activated for observation of timing marks on the engine. By adjusting the timing pulse width or delay of the strobe light such that illumination occurs at the time the piston reaches top dead center within the cylinder, as indicated by the timing marks on the dynamic damper, the width of the delay or timing pulse can be taken as representative of timing advance. Suitable apparatus is provided for reading the width of the timing or advance pulse in an analog or digital manner. Conversely, the desired advance angle may be set manually and the proper timing can be established by adjusting the advance angle until the strobe light coincides with the occurrence of piston top dead center within the cylinder. An alternate mode of system operation provides a readout of engine speed on the same meter used for timing readout. Appropriate switching and calibrating circuitry is included for this mode as well. Both the apparatus and method for the aforesaid timing system are disclosed, together with a plurality of transducers suitable for use with the system.