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 «Supply system» and «Engine management system».
In the feedback injection system, an exhaust gas catalytic converter and an oxygen concentration sensor in the exhaust gases are installed, which provides feedback. The sensor monitors the oxygen concentration in the exhaust gases, and the electronic control unit, using its signals, maintains such an air- fuel ratio at which the converter works most efficiently. On Renault Logan cars, a second oxygen concentration sensor can also be installed at the outlet of the converter. Moreover, the main control sensor is the sensor installed on the exhaust manifold, and the sensor installed at the outlet of the converter is diagnostic and determines the quality of the entire engine control system as a whole. If the engine control unit, according to 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 signals of the control sensor and which means some kind of system malfunction, it will turn on the engine malfunction warning lamp in the instrument cluster and enter the 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 allow the electronic control unit to heat up (ECU) above 65°C in working condition and above 80°C in non-working condition (e.g. in a drying chamber). It is necessary to remove the computer from the car if this temperature is exceeded.
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.
Make 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 ECU plugs or electronic components on its boards with your hands;
- - when working with a programmable read-only memory device (PROM) control unit, do not touch the microcircuit pins.
It is not allowed to work on leaded gasoline of an engine with a 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.
1. Check the connection with «weight» engine and battery.
2. Check the fuel pump and fuel filter.
3. Check the fuses and relays for switching on the elements of the injection system.
4. Check up reliability of contacts in blocks with wires of elements of system of injection.
5. Check the sensors of the injection system.
The vast majority of fuel injection system malfunctions are caused by the failure of the following sensors:
- top dead center sensor (TDC) and crankshaft speed (mounted on the clutch housing) - complete failure of the injection system, the engine does not start;
- throttle position sensor (mounted on throttle body) - loss of power, jerks and dips during acceleration, unstable operation in idling mode;
- 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;
- intake air temperature sensor - if the sensor fails, fuel consumption increases, the level of toxicity of exhaust gases increases;
- absolute pressure sensor (rarefaction) in the intake pipe - if the sensor fails, an increase in fuel consumption, a significant deterioration in dynamics, problems with starting the engine;
- knock sensor (installed on the right side of the cylinder block in the region of 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) installed on the exhaust manifold (for clarity, the thermal screen of the collector is removed) - increased fuel consumption, reduced engine power, unstable idling. Possible damage to the catalytic converter of exhaust gases;
- speed sensor (mounted on the gearbox housing) - possible deterioration of the dynamic qualities of the car and an increase in fuel consumption. Check the reliability of the wiring harness block to the sensor and clean its contacts from oxides.