LEXUS RX 300

1998 — 2003 of release

Repair and car operation

Principle of functioning of a control system of fuel injection

General information

Fuel is sucked in from a fuel tank by the electric fuel pump and moves via the fuel filter to the fuel distributive highway. The regulator of pressure provides pressure maintenance in fuel system in a range of 3.0 ÷ 3.4 atm.

Through electrooperated injectors fuel impulsno is injected into the inlet pipeline located directly ahead of inlet valves of the engine. The control unit the engine makes consecutive management of injectors according to ignition order, regulates injection time and by that amount of injected fuel.

The air necessary for formation of a fuel mix, is sucked in by the engine via the air filter and arrives through a butterfly valve, the air distributor and the inlet pipeline to inlet valves. The amount of soaked-up air is regulated by a butterfly valve. The volume of soaked-up air is defined by a measuring instrument of amount of the air (MAF), located on an air purifier cover.

The control unit the engine is in the lower right part of the dashboard. The control unit defines optimum time of ignition, the moment of injection and amount of injected fuel. Thus there is a coordination of operation of the control unit with other systems of the car.

Information from other sensors and the operating tension arriving to executive bodies, provides optimum operation of the engine in any situation. If some sensors fail, the control unit is switched in a mode of the emergency program to exclude possible damage of the engine and to provide further movement of the car.

Short description of principles of functioning of some of sensors and actuation mechanisms of a control system of the engine

The sensor of provision of a butterfly valve (TPS) is built in in the executive mechanism of a butterfly valve and issues on the module of management (ECM) information on the current coal of provision of a butterfly valve. The second potentiometer reports ECM data on base value and forms duplicating signal at failure of a potentiometer of a butterfly valve.

The sensor of provision of a cranked shaft (CKP) is established on the block of cylinders at a flywheel. It hands over to the control unit information on number of turns of a cranked shaft and finding of the piston of the first cylinder in VMT.

The sensor of provision of a camshaft (CMP) is located in an end face of a cover of a head of cylinders. It together with the sensor of provision of a cranked shaft hands over to the control unit information on VMT of the piston of the first cylinder. It serves for synchronization of the moment of ignition and sequence of ignition.

The sensor of temperature of cooling liquid (ECT) is located in a reception branch pipe of system of cooling (see illustrations Components of installation of the thermostat and Location Д/В of No. 1 and No. of 2 ECT). It represents the resistor with the negative temperature factor which resistance decreases with temperature growth.

The sensor of measurement of weight of air (MAF) represents the termoanemometrichesky measuring instrument which has been built in in an inlet air path of the engine. In the case of a measuring instrument the warmed touch film cooled by a passable stream of soaked-up air is located thin, electricly. The electric current which is heating up a film, is regulated by a control system so that to maintain temperature a constant film. If, for example, the amount of soaked-up air increases, the temperature of a heated-up film starts to decrease. Thus the size of an electric current increases at once to keep temperature of a plate invariable. Fluctuations of an electric current indicate to the control unit by the engine its loading that allows to define amount of injected fuel correctly. Information issued by the sensor is used by ECM at determination of parameters of a dosage of an air and fuel mix.

The sensor of a detonation (KS) is rolled directly in the block of cylinders and serves for prevention of emergence of dangerous shock combustion of a fuel mix, allowing to hold installation of the moment of ignition on detonation border when efficiency of return of the engine is supported at a maximum level at the minimum fuel consumption.

The system of ventilation of fuel tank/catching of fuel evaporations (EVAP) consists of a coal adsorber and the electromagnetic valve of management of a purge of the last. In an adsorber pairs of fuel which are forming as a result of its heating accumulate. At operation of the engine the fuel evaporations which have accumulated in an adsorber are extended to the inlet highway and go to combustion chambers.

Lambda probes measure the content of oxygen in the fulfilled gases (OG) before and after catalytic converters and transmit the corresponding signals in the control unit the engine.