Cranking Enrichment

Cranking Enrichment

During cranking when the engine speed is below a preset threshold speed of approximately 400 rev/min the ECM increases the injector pulse width to aid starting. The amount of increase varies depending upon coolant temperature. To prevent flooding the cranking pulses are intermittent (30 pulses on 16 pulses off).

After Start Enrichment

Additional enrichment is provided following cranking at all temperatures. The amount of additional fuel supplied is controlled by the ECM and will decay at a rate depending upon coolant temperature

To implement after start enrichment, the ECM increases the injector pulse width.

Acceleration Enrichment

During acceleration, additional fuel is required to ensure response is smooth. This enrichment is applied by the ECM which receives an output voltage (rising) from the throttle position sensor and a rise in manifold absolute pressure. This additional fuel is provided by increasing the injector pulse width and instigating additional pulses at 80o crank intervals.

Over-run Fuel Cut-off

Over-run fuel cut-off is implemented by the ECM when the following conditions exist:

Coolant temperature is above 80oC approx. Throttle closed. Engine speed above 1600 rev/min approximately.

Back Up Facility

In the event of certain input failures the ECM will implement a back-up air fuel ratio to maintain driveability. A back-up value is provided for the coolant sensor, inlet air sensor and manifold absolute pressure sensor.