The distributor shaft is driven by a gear on the camshaft on most overhead valve engines, and attached directly to a camshaft on most overhead cam engines. By the end of the 20th century mechanical ignitions were disappearing from automotive applications in favor of inductive or capacitive electronic ignitions fully controlled by engine control units (ECU), rather than directly timed to the engine's crankshaft speed.Ī distributor consists of a rotating arm or rotor inside the distributor cap, on top of the distributor shaft, but insulated from it and the body of the vehicle ( ground). Atwater Kent invented his Unisparker ignition system about this time in competition with the Delco system. This ignition was developed by Charles Kettering and was considered a wonder in its day. (Delco) and introduced in the 1910 Cadillac Model 30. The first reliable battery operated ignition was the Delco ignition system developed by Dayton Engineering Laboratories Co. Except in magneto systems and many modern computer controlled engines that use crank angle/position sensors, the distributor also houses a mechanical or inductive breaker switch to open and close the ignition coil's primary circuit. The distributor's main function is to route secondary, or high voltage, current from the ignition coil to the spark plugs in the correct firing order, and for the correct amount of time. Upper right is Distributor.Ī distributor is an enclosed rotating shaft used in spark-ignition internal combustion engines that have mechanically timed ignition.