Fuel system
Fuel is supplied by the fuel pump at a constant pressure difference (284 kPa) through the filter to the injectors, which inject fuel into the intake manifold pipes directly in front of the intake valves. The amount of fuel supplied is determined by the duration of the control pulse, which is set in accordance with the signal from the electronic control unit.
The fuel pressure regulator maintains a constant difference between the fuel pressure before the working injector and the air pressure in the intake manifold. In this case, the amount of fuel supplied is clearly determined by the open state of the injector. Regulation is carried out by bypassing part of the fuel into the tank through the valve and the fuel return line.
Air supply system
The air supply system ensures that the required amount of air is supplied to the intake valves.
The amount of air entering the engine is determined by the throttle valve opening angle and the engine crankshaft speed. The air flow passes the air filter, the throttle valve body channel and enters the upper part of the intake manifold, from where it is distributed through separate pipes to the engine cylinders.
At low coolant temperatures, the idle speed control valve opens and some air enters the upper intake manifold through the bypass passage in addition to the air passing through the throttle valve. Thus, as the engine warms up, even with the throttle valve fully closed, air enters the upper intake manifold, which causes the engine speed to increase (1st stage idle speed control).
The upper part of the intake manifold reduces air flow pulsations (functions as a receiver or resonator), and also prevents the work of some cylinders from overlapping with others.
Electronic control system
The engines are equipped with an electronic control system from TOYOTA, which controls fuel injection, ignition timing, diagnostic system, etc. using an electronic control unit.
By means of an electronic control unit, the fuel injection control system performs the following functions:
1. Fuel injection control. The electronic control unit receives signals from various sensors that record changes in the engine operating condition. In particular, the sensors record:
- absolute pressure in the intake manifold,
- intake air temperature,
- coolant temperature,
- engine crankshaft speed,
- throttle opening angle
- oxygen content in exhaust gases, etc.
These signals are processed in the electronic control unit, which generates an output signal for the fuel injection duration, ensuring the optimum excess air ratio for the current engine operating conditions.
2. Control of ignition timing angle.
The electronic control unit memory stores the values of the optimal ignition advance angle for all possible engine operating modes. Using signals from various sensors monitoring engine operating conditions (crankshaft speed, coolant temperature, etc.), the electronic control unit generates pulses that control spark formation at strictly defined moments in time.
3. Idle speed control system.
The electronic control unit memory stores data on the optimum idle speed, which corresponds to various conditions (for example, coolant temperature, air conditioning on/off, etc.) The sensors transmit signals to the electronic control unit, which controls the air flow through the bypass channel (bypassing the throttle valve) and regulates the idle speed in accordance with the set value.
Location of components of the electronic fuel injection control system.
1 - nozzle,
2 - knock sensor,
3 - additional throttle valve servo drive,
4 - absolute pressure sensor,
5 - throttle position sensor,
6 - additional throttle position sensor,
7 - electronic control unit of the traction control system (TRC),
8 - electronic control unit,
9 - fuel pump,
10 - oxygen sensor (3S-FE, front wheel drive),
11 - switch,
12 - diagnostic connector,
13 - idle speed control valve,
14 - circuit breaker relay,
15 - injection system fuse,
16 - main relay of the injection system,
17 - intake air temperature sensor,
18 - Distributor,
19 - coolant temperature sensor,
20 - oxygen sensor (4S-FE, 3S-FE, 4WD),
21 - oxygen sensor (3S-FE, front wheel drive),
22 - exhaust gas temperature sensor (4S-FE, 3S-FE, 4WD),
23 - fuse and relay box,
24 - crankshaft position sensor,
25 - ignition coil No.2,
26 - ignition coil No.2.
4. Diagnostics.
The electronic control unit warns of a malfunction or abnormal operation via an indicator "CHECK ENGINE", displayed on the instrument panel. The malfunction is identified as a diagnostic code, which is stored by the electronic control unit. The diagnostic code can be deciphered by the number of blinks of the indicator light when the contacts "TEG" and "EG" are shorted. Diagnostic codes are discussed below.
5. Function "Fail-Safe" ("Get home").
In case of failure of any sensor, an emergency mode of operation is provided (to get to the nearest service station). At the same time, the control lamp on the instrument panel lights up "CHECK ENGINE".