This section only briefly describes injection system malfunctions caused by failure of certain sensors. The procedure for removing and installing fuel and engine control system components is given in the subsections "Engine Fuel System" and "Engine Control System".
The feedback injection system includes a catalytic converter of exhaust gases and an oxygen concentration sensor in the exhaust gases (on the Ford Focus II, two converters and four oxygen concentration sensors are installed in parallel to each other), which provides feedback. The sensors monitor the oxygen concentration in the exhaust gases, and the electronic control unit, using their signals, maintains such an air-fuel ratio at which the converters operate most effectively. Moreover, the main control sensors are the sensors installed on the catalytic collector, and the sensors installed at the output of the converters are diagnostic, they determine the quality of operation of the entire engine management system as a whole. If the engine control unit, based on the information from the diagnostic sensors, detects an excess of oxygen concentration in the exhaust gases that cannot be eliminated by calibrating the system using the signals from the control sensors and indicates some kind of system malfunction, it will turn on the engine management system malfunction indicator lamp in the instrument cluster and enter the error code into memory for subsequent diagnostics.
WARNING: Before removing any fuel injection system components, disconnect the negative battery cable.
WARNING: Disconnect the battery only when the ignition is off.
WARNING: Do not start the engine if the battery cable terminals are not tight.
WARNING: Never disconnect the battery from the vehicle's electrical system while the engine is running.
WARNING: When charging, disconnect the battery from the vehicle's electrical system, as the increased charging current may damage the electronic components.
WARNING: Do not allow the electronic control unit (ECU) to heat up above 65°C when in operation or above 80°C when not in operation (e.g. in a drying chamber). The ECU must be removed from the vehicle if this temperature is exceeded.
WARNING: Do not disconnect or connect the wiring harness connectors to the ECU with the ignition on.
WARNING: Before performing arc welding on a vehicle, disconnect the battery cables and the ECU cable connectors.
WARNING: Make all voltage measurements using a digital voltmeter with an internal resistance of at least 10 megohms.
WARNING: The electronic components used in the injection system are designed for very low voltage and can be easily damaged by electrostatic discharge. To prevent damage to the ECU by electrostatic discharge:
WARNING: – Do not touch the ECU connectors or electronic components on its boards with your hands;
WARNING: – When working with the programmable read-only memory (PROM) of the control unit, do not touch the terminals of the microcircuit.
WARNING: Do not operate an engine with a catalytic converter on leaded gasoline - this will lead to rapid failure of the catalytic converter and oxygen concentration sensor.
WARNING: When operating in rainy weather, do not allow water to come into contact with the electronic components of the fuel injection system.
Check the injection system in the following order.
1. Check the ground connection of the engine and battery.
2. Check the fuel pump and its fuel filter.
3. Check the fuses and relays for switching on the injection system elements.
4. Check the reliability of the contacts in the pads with wires of the injection system elements.
5. Check the injection system sensors.
The vast majority of fuel injection system faults are caused by failure of the following sensors:
– crankshaft position sensor – complete failure of the injection system, the engine does not start;
- throttle position sensor (installed in the throttle cover) - loss of power, jerks and dips during acceleration, unstable operation in idle mode;
– coolant temperature sensor — difficulty starting in cold weather, as you have to warm up the engine, maintaining the speed with the accelerator pedal, when overheating, the power is significantly reduced, detonation appears;
– combined mass flow and intake air temperature sensor – if the temperature measurement function fails, fuel consumption increases, exhaust gas toxicity increases, and if the flow measurement function fails, fuel consumption increases, dynamics significantly deteriorates, engine starting problems occur;
– electromagnetic valve of the variable valve timing system – if the valves fail, there is a significant deterioration in dynamics and "floating" of the crankshaft speed in idle mode up to a complete stop of the engine;
NOTE: The engine shown has two solenoids, one each for the intake and exhaust camshafts.
– knock sensor (two sensors are installed on the left side of the cylinder block in the area between the 1st and 2nd…
…and also between the 3rd and 4th cylinders) – the engine is very sensitive to the quality of gasoline, increased tendency to detonation;
– oxygen concentration sensor in the exhaust gases (lambda probe) – increased fuel consumption, decreased engine power, unstable idling. Possible damage to the catalytic converter of the exhaust gases;
– phase sensor – power loss, fuel consumption increase;
NOTE: The engine shown has two camshaft position sensors, one for each intake and exhaust camshaft.
– speed sensor (installed on the gearbox housing) – possible deterioration of the vehicle"s dynamic qualities and increase in fuel consumption.