Engine Control Module: Description and Operation

Fuel metering is obtained by controlling the injector pulse during each engine cycle. The pulse duration is varied by the ECU according to inputs from the various sensors.
The control parameters fall into two groups.
The first consists of intake manifold pressure and engine speed.
Information on engine speed received by the ECU is obtained from the ignition coil negative terminal via a 6.8 ohm resistor located inside the AB14 ignition amplifier.
The intake manifold pressure is sensed by a transducer located inside the ECU and linked to the intake manifold by vacuum tubing. The transducer is an integral part of the ECU and cannot be replaced without recalibrating the electronic circuits.
The fueling information for the engine is stored in a preprogrammed memory so that for any combination of manifold pressure and engine speed, the memory gives out a number which is proportional to the amount of fuel required by the engine. The injectors will be energized for a time proportional to the number computed plus what is sensed by the secondary control parameters.
The second control parameters consist of engine coolant temperature, inlet air temperature, throttle movement, closed loop and battery voltage.