With Automatic Transmission

FUEL INJECTION

As the engine is turned by the starter motor, the Engine Speed sensor (7/25) and Camshaft Position sensor (7/21) deliver engine speed and crankshaft position signals to the ECM, which opens the injectors once per working cycle to inject fuel.

One terminal of each injector connector is supplied with 12 Volts from the main relay, while the second is connected to the ECM, which operates the injectors by grounding the appropriate lead.

During the start-up phase, the ECM computes the injection period on the basis of the engine temperature and speed signals.

When the engine is running, the injection period is based on the engine speed, temperature and load, battery voltage, and other parameters.

The ECM opens the injectors individually in what is known as Sequential Fuel Injection (SFI), enabling the fuel to be injected at the optimum instant to achieve a homogeneous air/fuel mixture. In normal operation, injection takes place just before the injectors open.

When the Heated Oxygen Sensor (7/15) (or the two HO2S installed in certain markets) has reached working temperature, the signal is also used in computing the fuel quantity.

The ECM compensates for variations in battery voltage, acceleration and load, and also controls the fuel cut-off function during engine braking. In addition, the system incorporates adaptive (self-learning) functions, which store information regarding optimum fuel injection under different running conditions. The ECM uses this information to compensate for wear and tolerances in system components, reducing exhaust emissions, maintenance requirements and the need for adjustment.

In the event of knock, if the phenomenon is not eliminated by retarding the timing, additional fuel is injected to reduce the temperature of the combustion process.

The ECM interrupts fuel injection if the speed of the car reaches 250 km/h (155 mph) or the engine speed reaches a maximum of 6200 rpm, and under engine braking conditions.

If the engine is over-revved, the ECM will cut off the fuel supply to prevent damage. The speed is permitted to rise to approx. 6500 rpm for 2.5 seconds and is thereafter limited to approx. 6200 rpm.

Fuel is also shut off during engine braking provided engine speed is above 1800 rpm (1920 rpm on cars with automatic transmission), provided the throttle is in the shut position (idling) and engine coolant temperature has reached a specific level. Once engine speed drops below 1200-1800 rpm (1200-1920 rpm on cars with automatic transmission) fuel injection resumes.