This section only briefly describes the malfunctions of the injection system caused by the failure of certain sensors. The procedure for removing and installing components of power supply and engine control systems is given in subsections Engine power system and Engine management system.
In the feedback injection system, an exhaust gas catalytic converter and oxygen concentration sensors in the exhaust gases are installed, which provide feedback. The sensors monitor the oxygen concentration in the exhaust gases, and the electronic control unit, based on their signals, maintains such an air-fuel ratio at which the converter works most efficiently. Moreover, the main control sensor is the sensor installed on the exhaust manifold, and the sensor installed at the outlet of the converter is called diagnostic, it determines the quality of the entire engine management system as a whole. If the engine control unit, based on the information of the diagnostic sensor, detects an excess of oxygen concentration in the exhaust gases, which cannot be eliminated by calibrating the system according to the signal of the control sensor and which means some kind of system malfunction, it will turn on the signal lamp 41 in the instrument cluster (see instrument cluster, pic. 1) engine management system and enters an error code into memory for subsequent diagnostics.
Attention!
- Before removing any components of the fuel injection system, disconnect the wire from the terminal «minus» battery. Disconnect the battery only when the ignition is off. Do not start the engine if the cable lugs on the battery are loose.
- Never disconnect the battery from the vehicle's electrical system while the engine is running. When charging, disconnect the battery from the car's on-board network, as the increased current during charging can damage the electronic components. Do not disconnect or connect the wiring harness connectors to the ECU while the ignition is on. Before performing arc welding on a vehicle, disconnect the wires from the battery and the wire connectors from the ECU.
Perform all voltage measurements with a digital voltmeter with an internal resistance of at least 10 MΩ. The electronic components used in the injection system are designed for very low voltage, so they can easily be damaged by electrostatic discharge. To prevent damage to the ECU by electrostatic discharge:
- do not touch the computer plugs or electronic components on its boards with your hands;
- when working with programmable read-only memory (PROM) control unit, do not touch the microcircuit pins.
It is not allowed to work on leaded gasoline of an engine with an exhaust gas converter - this will lead to a quick failure of the converter and oxygen concentration sensors. When working in rainy weather, do not allow water to enter the electronic components of the fuel injection system.
Check the injection system in the following order.
- Check engine and battery connection with «weight».
- Check the fuel pump and its fuel filter.
- Check the fuses and relays for switching on the injection system elements.
- Check the reliability of the contacts in the blocks with wires of the injection system elements.
- Check injection sensors.
The vast majority of fuel injection system malfunctions are caused by the failure of the following sensors:
- crankshaft position sensor (the photo shows the connector of the sensor wiring harness block, mounted on the cylinder block behind the starter, the sensor itself is located inside the engine, so it can only be accessed after removing the gearbox, clutch and flywheel) - Complete failure of the injection system, the engine does not start;
- throttle position sensor (installed in the throttle body cover) - loss of power, jerks and dips during acceleration, unstable idling;
- coolant temperature sensor - difficulties with starting in cold weather: you have to warm up the engine, maintaining the speed with the accelerator pedal, when overheating, power decreases significantly, detonation appears;
- combined mass flow and intake air temperature sensor - if the temperature measurement function fails, an increase in fuel consumption and exhaust gas toxicity, and if the flow measurement function fails, an increase in fuel consumption, a significant deterioration in dynamics, problems with starting the engine;
- solenoid valve of the variable valve timing system - in case of valve failure, a significant deterioration in dynamics and «swimming» crankshaft speed in idle mode up to a complete stop of the engine;
Note. The engine shown has two solenoid valves, one each for the intake and exhaust camshafts.
- knock sensor (installed on the left side of the cylinder block in the area between the 2nd and 3rd cylinders) - the engine is very sensitive to the quality of gasoline, increased tendency to detonation;
- exhaust oxygen concentration sensor (Lambda probe) – increased fuel consumption, reduced engine power, unstable idling. Possible damage to the catalytic converter of exhaust gases;
- phase sensor - power reduction, increased fuel consumption;
Note. The engine shown has two phase sensors, one each for the intake and exhaust camshafts.
- speed sensor (the location of its possible installation on the gearbox housing is shown, since it is not installed on the car used for photography, instead, the speed sensor of the left front ABS wheel is used to obtain speed information) – deterioration of dynamic qualities of the car and increase in fuel consumption is possible;
- solenoid valve and pneumatic actuator of the system for changing the geometry of the intake pipe - deterioration of the dynamic qualities of the car and increase in fuel consumption are possible.
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