Description & Operation

Isuzu Pickup models equipped with carbureted (4DZ1) engines use a breakerless electronic ignition system consisting of a reluctor, distributor pick-up coil, ignition coil, vacuum advance and mechanical advance weights.

On Impulse, Trooper II and EFI equipped Pickup models, a crank angle sensor is built into the distributor housing. The crank angle sensor uses a photoelectric pick-up and rotor plate to measure engine speed and piston position. On Impulse models, a switching transistor is mounted on the side of the ignition coil. On Trooper II and EFI equipped Pickup models, a power transistor unit is in-line between the ECM and the ignition coil. This transistor is controlled by the ECM and triggers the ignition coil.

The Electronic Control Module (ECM) uses inputs from this crank angle sensor to control the distributor advance curve. The ECM is part of the Isuzu I-TEC engine control system. Other sensor inputs to the ECM which control ignition timing advance are as follows: coolant temperature sensor, vehicle speed sensor, airflow sensor, throttle valve switch and knock sensor (Impulse).