Fuel Injectors

Fuel Injectors 

The fuel injector is a solenoid device that is supplied a high voltage supply circuit and a high voltage control circuit from the ECM. Electrical pulses are supplied by the ECM to each fuel injector at the correct time and sequence determined by information received from the camshaft position sensor. When the fuel injector receives electrical pulses, fuel is sprayed from the fuel injector tip directly into the combustion chamber on the compression stroke of the engine. The fuel injectors are located above each cylinder and deliver fuel directly into the cylinder. Each injector has a high pressure fuel pipe from the fuel rail and a return line.

Fuel Injection Quantity 

In the calibration / controls community this is referred to as the Fuel Setpoint Adaptation (FSA). An algorithm is used to estimate the actual injected fuel quantity. This estimated quantity is used to correct ECM set points for items such as exhaust gas recirculation (EGR), Boost Pressure, Fuel Rail Pressure, etc.. The goal of FSA is to account for injectors that drift during the lifetime of the vehicle. The algorithm estimates the real injected fuel quantity by using input from the mass airflow (MAF) sensor & nitrogen oxides (NOx) sensor 1 to determine the air/fuel ratio.

Fuel Injection Timing 

The engine control module (ECM) has the ability to learn injector timing performance. When the engine is at operating temperature, throttle closed and in deceleration fuel cut-off mode, the ECM will pulse each injector individually and measure the changes in rotational speed of the crankshaft using the input from the crankshaft position sensor. The ECM will run this diagnostic at one fuel rail pressure operating point for each injector. The ECM stores the injector timing value.