Electronic Fuel Injection (EFI) System — General Information (Nissan Maxima A32)

All vehicles covered in this Manual are equipped with an electronic multipoint fuel injection (EFI) system. Injection is carried out sequentially into the intake ports of each combustion chamber in the order of ignition and in the amount determined by the current needs of the engine. There is one injection injector for each engine cylinder. The injectors are mounted on the intake manifold assembly, the upper section of which is a pressure chamber that provides optimal conditions for air supply to the intake tract and its dosage by a removable throttle chamber (throttle body).

The main component (think tank) injection system is an on-board processor, also called the powertrain control module (PCM). The PCM analyzes continuously incoming data from various information sensors and calculates the optimal air-fuel mixture for the current moment. The system also provides automatic compensation for changes in external factors such as the vehicle's altitude above sea level, engine load and speed.

Fuel is supplied to the system tract by means of a high-pressure submersible electric fuel pump. Pumped through the fuel filter, the fuel enters the fuel line of the EFI system via the fuel line system.

The fuel line assembly includes electric injectors that perform metered injection of fuel directly into the intake ports of the engine combustion chambers. In addition to the injectors, the fuel line assembly also includes a fuel pressure regulator that constantly maintains the fuel pressure at a given level. Excess fuel entering the line is diverted back to the fuel tank via the return fuel line.



Injectors are constant-run electromagnetic valves. The main components of the injector are: a control solenoid, a plunger, and a needle valve. All of these parts are placed in a common housing. When electric current passes through the solenoid coil, the needle valve opens slightly, fuel under pressure fills the cavity of the injector housing and is injected through the nozzle into the combustion chamber of the corresponding cylinder. The amount of injected fuel is determined by the duration of the valve opening time, i.e., the duration of the voltage supply to the solenoid coil. In order to limit the current passing through the injectors, resistors are included in the wiring of the circuits of the latter.

The duration of the injectors' activation is controlled by the PCM. The module's memory contains basic values of the valve opening time for various combinations of input parameters (engine speed, amount and temperature of intake air). The necessary information is sent to the module in the form of signals from the corresponding engine sensors.