Isuzu G-series Twin Cam

Delco 4 cyl ignition circuit

Hacked together from a couple of sources:



The ignition module converts the AC wave from the reluctor in to a DC square wave. This is fed back to the ecu, and below 400 RPM switches the coil giving 10 degrees constant advance for start up. If you were to disconnect the 4 pin connector you should still get spark with constant advance at any rpm.

Then above 400 RPM the ECU raises the bypass line which switches the relay and the square wave then comes from the ECU which includes the programmed advance in the timing. This is normal operation.

The module switches the coil negative.