Fuel Control System Operation: Notes

The function of fuel metering system is to deliver correct amount of fuel to engine under all operating conditions. The fuel is delivered to engine by individual fuel injectors mounted into intake manifold near each cylinder.

The two main fuel control sensors are Manifold Absolute Pressure (MAP) sensor and Oxygen Sensor (02S).

The MAP sensor measures or senses intake manifold vacuum. Under high fuel demands MAP sensor reads a low vacuum condition, such as wide open throttle. The powertrain control module (PCM)/engine control module (ECM) uses this information to richen mixture, thus increasing fuel injector on-time, to provide correct amount of fuel. When decelerating, vacuum increases. This vacuum change is sensed by MAP sensor and read by PCM/ECM, which then decreases fuel injector on-time due to low fuel demand conditions.