Fuel is pumped from the fuel tank by an electric fuel pump and fed through the fuel filter to the distribution line and then to the injection valves. The pressure regulator on the line ensures constant pressure in the fuel system when the vacuum pressure of the suction changes. The sucked air is cleaned in the air filter and fed to the engine through the intake manifold.
The air filter housing contains an air mass meter that measures the amount of incoming air and transmits this information to the control unit in the form of electrical pulses. Based on these pulses and engine speed signals, the engine control unit roughly calculates the fuel injection moment. To more accurately determine the injection moment, signals from other sensors are also used, such as the atmospheric pressure meter or intake air temperature sensor.
The injection/ignition system control unit processes the data coming from the sensors and calculates the injection moment and the amount of fuel injected based on the parameter field stored in its memory. With a longer opening of the injection valve (injector), more fuel will be injected per one crankshaft revolution. Injection is performed sequentially, i.e. the injection valves are controlled separately in the ignition sequence.
The lambda probe (oxygen sensor) measures the oxygen content in the exhaust gases and transmits information to the control unit in the form of voltage. The control unit changes the ratio between fuel and air in the mixture based on this information so that the exhaust gases burn in the catalytic converter in an optimal way.
The fuel tank air release valve is controlled depending on the engine operating mode. The evaporated fuel in the fuel tank is accumulated in the activated carbon filter and released through the combustion valve. Thus, fuel vapors are mostly used economically and are not released into the air.
(The original material is posted on the website: www.mitsubishiman.ru)
MPI injection device diagram
The picture shows a 1.5L engine
MPI Fuel Supply
The picture shows a 1.5L engine
The control unit is located in the passenger compartment on the right side next to the glove compartment.
The fuel pump is located in the fuel tank and is immersed in the fuel. This reduces noise and the formation of fuel bubbles. The safety valve opens at a pressure of 4.5-6 bar and thus prevents excessive pressure build-up in the fuel line. The check valve maintains the pressure in the fuel line when the engine is stopped on the distribution line and constantly maintains the pressure at 3.3 bar higher than the pressure in the intake manifold. The pressure value is therefore around 2.7 bar (turbo engine 2.55 bar).
The injection valves (injectors) are controlled by the control unit and during the operation of the injection device. When current flows through the winding of the electromagnet, the needle of the injection valve is drawn in and fuel is injected. When the current circuit is broken, the spring returns the needle and the valve is locked.
The throttle body contains a throttle valve, which regulates the amount of air through the gas pedal. In addition, the throttle body contains an idle speed adjustment mechanism.
The idle speed controller (setting motor) regulates the air supply bypassing the throttle valve. Thanks to it, the engine speed is stabilized during the warm-up phase. The idle speed controller contains the setting motor position sensor and the idle speed switch sensor.
Caution: When working with the injection device and fuel lines, keep the area clean, see p. 6.2.