Engine analyzer power check apparatus

Abstract

An engine analyzer tests operation of a multicylinder internal combustion engine by disabling selected cylinders. The apparatus includes a semiconductor switch connected in parallel with the ignition points (or solid state circuit interrupter) of the engine's ignition system. A cylinder clock signal is derived from the engine, and exhibits a first signal transition each time the points open. A cylinder counter maintains a cylinder count identifying the current cylinder, and a period measurement timer measures the time period for each cylinder based upon the time between each first signal transition of the cylinder clock signal. The previously measured time periods of the cylinders are stored in a table which is constantly updated. Each time a first signal transition occurs, a programmable time delay timer is loaded with an input value which is based upon a previously measured time period for the current cylinder. The time delay is shorter than the previously measured time period, so that the time delay ends before the first signal transition corresponding to the next cylinder in sequence. An enable/disable table is stored which indicates which cylinders are to be disabled. If the next cylinder in the sequence is to be disabled, the switch is switched from a nonconductive to a conductive state so as to short circuit the points to prevent generation of a secondary voltage for the ignitier corresponding to the next cylinder.