Distributor Ignition (DI) System

Distributor Ignition (DI) Input/Output Chart:

CIRCUIT OPERATION
The ignition timing is controlled by the ECM to help maintain the best blend of engine performance and emissions under all operating conditions.

The ECM uses several sensors to calculate the amount of timing based on a map stored in its memory. The ECM varies the timing during:
^ Starting
^ Warm up
^ Idle
^ Hot engine operation
^ Acceleration
^ Low battery voltage
^ Engine ping

Power Transistor:

POWER TRANSISTOR
The power transistor, located near the base of the distributor, is a voltage amplifier that allows the signal sent from the ECM to activate the primary circuit in the ignition coil. This induces high voltage in the secondary windings of the ignition coil, providing spark to the distributor cap and plugs.

Ignition Coil:

IGNITION COIL
The Ignition Coil, located near the base of the distributor, receives the on/off signals from the Power Transistor and will step up the voltage from 12 Volts to 20,000 Volts (or more) to jump the spark plug gap.