Circuit description
The fuel pump is located inside the fuel tank and is connected to the fuel line. The fuel pump will remain on as long as the starter is engaged or the engine and engine control unit are running (ECM) receives a pulse signal from the crankshaft position sensor (TFR). If there are no pulse signals, the ECM will turn off the fuel pump after 2 seconds with the ignition on or 2 seconds after the engine is turned off. The fuel pump delivers fuel through the fuel manifold to the fuel injectors, where the pressure level is maintained at 379 to 393 kPa by the fuel pressure regulator. Excess fuel is returned to the fuel tank.
There are two main fuel control sensors:
- manifold absolute pressure sensor (IDA),
- oxygen sensor (O2S).
Manifold absolute pressure sensor (IDA)
The MAP sensor measures the vacuum in the intake manifold.
When there is a high demand for fuel, the MAP sensor provides information about low vacuum, which corresponds to a large throttle opening angle. The engine control unit (ECM) uses this data to richen the mixture, increasing the injector valve opening time to provide the required amount of fuel. As the throttle opening angle decreases, the vacuum increases. This change in vacuum is sensed by the manifold absolute pressure sensor and the ECM, resulting in reduced fuel injector turn-on time and reduced fuel delivery.
Oxygen sensor (O2S)
The oxygen sensor is located on the exhaust manifold. oxygen sensor (O2S) provides the ECM with data on the amount of oxygen in the exhaust gases, and the ECM changes the air / fuel ratio using injectors. The best air/fuel ratio to minimize harmful impurities in the exhaust gases is 14.7:1, which allows the catalyst to work more efficiently.
Due to the constant measurement and adjustment of the air/fuel ratio, the fuel injection system is called the «closed circuit».
The ECM receives input from various sensors to determine the correct amount of fuel to supply to the engine. Fuel is supplied according to one of the condition schemes called «mode».