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.

Abstract: An ignition analyzer apparatus tests the condition of the ignition coil of an internal combustion engine. A gating pulse is supplied to a test circuit immediately before the points are to open for a selected cylinder which causes the test circuit to provide a low resistance in parallel with the points when the points open. This allows a reduced primary current to flow through the ignition coil and prevents the production of a voltage pulse large enough to fire the spark plug for the selected cylinder. While the points are open and the test circuit is providing a low resistance path, the primary current flowing through the coil is measured. The gating pulse ends approximately half-way between the "points open" time of the selected cylinder and the "points open" time of the next cylinder so that the rotor of the distributor is between distributor terminals.

Abstract: An engine analyzer for an internal combustion engine includes an analog-to-digital (A/D) converter which digitizes an analog electrical input waveform representing, for example, a secondary or primary voltage waveform of the ignition coil of the internal combustion engine. The digitized input waveform is stored in the form of digital data in a data memory. Upon request by the operator of the apparatus, a microprocessor selects digital data stored, and supplies that digital data to a display, which displays a visual representation of the waveform based upon the selected digital data.

Abstract: Engine timing apparatus includes a timing light, cylinder clock signal circuitry, a cylinder counter, a cylinder comparator, first, second and third timers, a trigger pulse generator, operator control buttons, and a computer. The first timer measures a first time period between firing of the No. 1 cylinder, and the second timer measures a second time period between firing of the cylinder preceding No. 1 and the firing of the No. 1 cylinder. The computer derives from the first and second time periods a first digital value which represents the angular degrees from firing of the cylinder preceding No. 1 to firing of the No. 1 cylinder. Each time the comparator output signal is produced, the third timer initiates an adjustable time period, and the trigger pulse generator triggers the timing light at the end of the adjustable time period. The operator control buttons include buttons which cause a second digital value to be increased or decreased.

Abstract: The condition of a storage battery of an internal combustion engine powered vehicle is tested automatically, and an indication of battery condition is provided to the service technician. The battery testing apparatus is connected to the positive (+) and negative (-) terminals of the battery to measure battery voltage under several different conditions. In particular, the battery testing apparatus measures battery voltage under open circuit conditions, while subjecting the battery to a predetermined AC load, and while subjecting the battery to a predetermined DC load. The battery testing apparatus also includes a temperature probe which measures the temperature of the battery.

Abstract: Apparatus for measuring the ignition timing of an internal combustion engine of the type having a pulse generator for indicating when the flywheel is in a predetermined position subsequent to top dead center and in which a pulse of predetermined amplitude is initiated by a signal from one spark plug and is terminated by a signal derived from the pulse generator. Correction is made for the reference angle between the top dead center position of the piston and the occurrence of the signal from the pulse generator by algebraically adding to the pulses a DC correction which is adjusted to conform with the known reference angle. The adjusted pulses are applied to a meter to indicate the amount of ignition advance or retard. A second meter indicates the amount of the correction voltage. The apparatus also has novel calibrating means for applying to the timing device two spaced voltage pulses spaced apart by the distance of a half cycle of a periodically varying commercial voltage of known frequency.

Abstract: Engine diagnostic apparatus for displaying on a cathode ray tube the voltage conditions existing at each of the spark plugs which apparatus is intended for use with ignition systems in which the voltage pulses applied to the spark plugs are of such short duration that a cathode ray tube will not properly respond to the changes of voltage. The apparatus is effective to successively charge a capacitor to a value corresponding to the value of each voltage pulse and the voltages across this capacitor are used to control the vertical defection of the cathode ray tube. At the end of a first period of time following a voltage pulse, the capacitor is shorted. The capacitor is maintained shorted for a longer period of time less than the time between successive pulses so as to avoid undesired charging of the capacitor as a result of transient conditions.