Method of identifying combustion engine firing sequence without firing spark plugs or combusting fuel

The invention relates generally to a method and apparatus for identifying a cylinder undergoing a compression stroke in an internal combustion engine. More particularly, the invention pertains to a method and apparatus for rapidly identifying a compression cylinder of an internal combustion engine during startup of the engine, in order to establish a proper ignition timing sequence. A method and apparatus for the precombustion identification of a cylinder undergoing compression in an internal combustion engine is disclosed. An electrode gap (e.g., preferably a spark plug) is disposed within a cylinder of an internal combustion engine. The electrode gap is provided with a voltage differential from a power supply through a circuit (preferably an RC circuit). The engine is cranked, and the voltage differential across the electrode gap is monitored during the cranking of the engine. With appropriate choices of the voltage differential across the electrode gap, the resistance R of the circuit, and the capacitance C of the circuit, voltage pulses are produced across the electrode gap during such time when the cylinder is not undergoing a compression stroke. Such voltage pulses are suppressed when the cylinder is in fact undergoing a compression stroke due to a rise in the breakdown voltage across the electrode gap, in accordance with Paschen's Law. The presence or absence of the voltage pulses is preferably converted into a binary output that is indicative of the occurrence of a compression stroke in the cylinder being monitored.