Ignition Systems: DISTRIBUTORLESS

Distributorless ignition system is controlled by ECM. System consists of 2 ignition coils and a power transistor assembly. Power transistor assembly consists of 2 transistors which control primary current through each ignition coil. One transistor controls coil which fires cylinders No. 1 and 2. Other transistor controls ignition coil which fires cylinders No. 3 and 4.

Although each coil fires 2 plugs simultaneously, ignition takes place in only one cylinder, since other cylinder is on its exhaust stroke when plug fires. Based on input from crankshaft and camshaft angle sensors, ECM sends signals to appropriate power transistor, which turns ignition coil on and off.