Abstract: Methods, apparatus, and systems for distinguishing between compression and exhaust strokes of a four-cycle engine is provided. A first ionization time of a spark plug for a known cylinder is measured on a first engine stoke. A second ionization time of the spark plug is measured on a second engine stroke. The second ionization time is compared to the first ionization time. It is determined that the engine stroke with the greater ionization time is a compression stroke.

Abstract: An ignition coil with an isolated internal lead in proximity to the secondary side can be used in a capacitive discharge ignition system with a microprocessor-based signal-processing module to monitor system performance. The diagnostic lead is fed into a diagnostic signal interface circuit that provides a logic edge to the microprocessor when the spark plug fires. By measuring the time from the firing signal provided by the microprocessor to the logic edge provided by the diagnostic signal interface circuit, the precise energy necessary to fire the plug can be determined. An ignition system that includes an ignition coil with a diagnostic lead can extend spark plug life by automatically adjusting spark energy to minimize wear on the spark plug.

Abstract: Apparatus, and a corresponding method for its operation, for controlling the air/fuel ratio in a large engine having one or more banks of cylinders with separate intake and exhaust manifolds. Oxygen sensors in the manifolds are sampled periodically to provide the apparatus with an indication of the level of oxygen, and therefore an indication of the level of various pollutants, in exhaust gases discharged from the engine. The apparatus, preferably in microprocessor form, computes a fuel control correction based on the difference between the sensed oxygen level and a desired oxygen level in each exhaust manifold. The correction is applied in the form of a change to the pulse width of a binary control signal applied to a solenoid valve. In the illustrative embodiment, the solenoid valve is coupled to a fuel pressure regulator and functions to vent an air chamber in the regulator when the solenoid is actuated.

Abstract: A method of and apparatus for enabling at least one spark plug of a internal combustion engine to provide a fuel igniting spark at a selectable time in the engine cycle is disclosed. Sensors provide a first engine rotation determined pulse train the repetition rate of which is the same as the number of revolutions per second of the engine and a second engine rotation determined pulse train the repetition rate of which is an integral multiple of that of the first pulse train. The reference pulse initiates a count of pulses in the second pulse train and, upon reaching a preselected count, initiates a count of pulses in a third independent pulse train having a much greater repetition rate. The spark plug is enabled when the third pulse train count reaches a preselected count.