There are distributed injection systems with and without feedback. Moreover, both systems can have both imported and domestic components. All systems have their own features of the device, diagnostics and repair, which are described in detail in separate repair manuals for fuel injection systems.
This chapter only briefly describes the general principles of the design, operation and diagnostics of fuel injection systems, the procedure for removing / installing components, and also provides features for repairing the engine itself.
The feedback system is mainly used on export vehicles. At the same time, a catalytic converter and an oxygen sensor are installed in the exhaust system, which provides feedback. The sensor monitors the oxygen concentration in the exhaust gases, and the electronic control unit, using its signals, maintains the air / fuel ratio at which the converter works most efficiently.
In an open-loop injection system, there is no converter and oxygen sensor; a CO potentiometer is used to adjust the CO concentration in the exhaust gases. The system for catching gasoline vapors is also not used.
Attention! Before removing any components of the injection control system, disconnect the wire from the terminal "–" battery.
Attention! Do not start the engine if the cable lugs on the battery are loose.
Attention! Never disconnect the battery from the vehicle's electrical system while the engine is running.
Attention! When charging the battery, disconnect it from the car's on-board network.
Attention! 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.
Attention! Do not disconnect or connect the wiring harness connectors to the ECU while the ignition is on.
Attention! Before performing arc welding on a vehicle, disconnect the wires from the battery and the wire connectors from the ECU.
Attention! Make all voltage measurements with a digital voltmeter with an internal resistance of at least 10 MΩ.
Attention! 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.
Attention! It is not allowed to operate the engine with a converter on leaded gasoline. This will lead to a quick failure of the converter and the oxygen concentration sensor.
Scheme of the injection system
1. Air filter; 2. Mass air flow sensor; 3. Hose inlet pipe; 4. Coolant supply hose; 5. Throttle pipe; 6. Idling regulator; 7. Throttle position sensor; 8. Idling system heating channel; 9. Receiver; 10. Pressure regulator hose; 11. Electronic control unit; 12. Relay for turning on the electric fuel pump; 13. Fuel filter; 14. Fuel tank; 15. Electric fuel pump with fuel level sensor; 16. Drain line; 17. Supply line; 18. Pressure regulator; 19. Inlet pipe; 20. Ramp nozzles; 21. Nozzle; 22. Speed sensor; 23. Oxygen concentration sensor; 24. Downpipe muffler; 25. Gearbox; 26. Cylinder head; 27. Outlet pipe of the cooling system; 28. Coolant temperature sensor; A. To the supply pipe of the coolant pump
The engine compartment of a car with an injection system
1. Ramp with nozzles; 2. Throttle body; 3. Air duct; 4. Fuse block; 5. Engine; 6. Receiver; 7. Throttle cable; 8. Air filter housing
Diagnostics
This is only a summary of the injection system diagnostics using the CHECK ENGINE warning lamp. Diagnostics using special devices and diagnostic cards is described in separate repair manuals for multipoint fuel injection systems.
The ECU constantly performs self-diagnostics for some control functions. The language used by the ECU to indicate the source of the problem is diagnostic codes. Codes are two-digit numbers ranging from 12 to 61. Different control units may have slightly different fault codes. The table shows the interpretation of the fault codes of the electronic control unit type "January–4" for a system of distributed fuel injection without feedback and with domestic components.
When the ECU detects a malfunction, the code is entered into "memory" and the CHECK ENGINE warning light comes on. This does not mean that the engine should be stopped immediately, but the cause of the warning light should be identified as soon as possible.
ECU Type Fault Codes "January–4"
Code | Malfunction |
12 | Serviceability of a diagnostic circuit of a control lamp |
14 | High coolant temperature sensor signal |
15 | Low coolant temperature sensor signal |
16 | Increased voltage of the on-board network |
17 | Reduced voltage of the on-board network |
19 | Incorrect crankshaft position sensor signal |
21 | Throttle position sensor signal voltage too high |
22 | Insufficient Throttle Position Sensor Signal Voltage |
24 | Missing vehicle speed sensor signal |
27 | CO potentiometer signal high |
28 | Low signal CO-potentiometer |
33 | Wrong mass air flow sensor signal (high frequency signal at the output of the sensor) |
34 | |
35 | Wrong mass air flow sensor signal (low frequency signal at the output of the sensor) |
43 | |
51 | Intermittent idle speed |
52 | Incorrect knock sensor signal |
53 | Programmable read-only memory error (PROM) |
61 | Electronic control unit error (RAM) |
CHECK ENGINE lamp
The lamp is located on the instrument panel and performs the following functions:
- informs the driver that a malfunction has occurred in the engine management system and the car needs to be checked;
- issues diagnostic codes stored in "memory" ECU to help the technician find the problem.
When the ignition is turned on, the lamp lights up, and while the engine is still not running, the lamp and systems are checked for serviceability. After starting the engine, the lamp should go out. If the lamp remains on, the self-diagnosis system has detected a malfunction. If the fault disappears, then the lamp goes out usually after 10 seconds, but the fault code will be stored in "memory" ECU.
If the fault is intermittent, the CHECK ENGINE lamp will illuminate for about 10 seconds and then turn off. However, the corresponding fault code will be stored in "memory" ECU until its power is turned off. When unexpected codes are found during the reading of codes, it can be assumed that these codes are created by an intermittent malfunction and will help in diagnosing the system.
Reading codes
The diagnostic block is used to communicate with the computer. It is located under the instrument panel on the right side next to the ECU.
Fault codes stored in "memory" ECU can be read with a special diagnostic tool or by counting the number of flashes of the CHECK ENGINE lamp.
To read the codes, the lamp must be connected to "weight" contact in the diagnostic pads. To do this, connect it to pin A, which is connected to "weight" engine.
A - contact connected to "weight"
B - diagnostic contact for signaling the ECU
G - contact for controlling the electric fuel pump
M - contact for issuing information (serial data channel)
When pins A and B are connected, turn the key in the ignition switch to position I (ignition), while the engine must not be running. Under these conditions, the CHECK ENGINE lamp should flash the code three times in a row "12".
This should happen in this order: flash, pause (1–2 s), flash, flash - long pause (2–3 s) and so two more times.
Code "12" indicates that the ECU diagnostic system is working. If the code "12" is not displayed, it means that the diagnostic system itself is faulty.
After flashing the code "12" the CHECK ENGINE lamp flashes fault codes three times, if any, or simply continues to flash the code "12", if there are no fault codes.
If more than one fault code is stored in the ECU memory, each of them is displayed three times.
Attention! At the end of the diagnostics, it is allowed to open contacts A and B of the diagnostic block 10 s after the ignition is turned off.
Erasing codes
Erase codes from "memory" ECU after the repair is completed or to see if the malfunction occurs again. To erase, you must turn off the power to the computer for at least 10 seconds.
The power can be turned off by disconnecting the wire from the terminal "–" battery or by removing the ECU protection fuse from the fuse box.
Attention! In order not to damage the computer, it is necessary to turn off and turn on its power only when the ignition is off.
Distinctive features of injection systems
Controller | General Motors | "January–4" |
Controller marking | 2111–1411020–20 | 2111–1411020–22 |
catalytic converter | Eat | No |
crankshaft position sensor (Sensors are not interchangeable, check the specific number directly on your car) | 2112–3847010, 2112–3847010–01 | |
Throttle position sensor (Sensors are not interchangeable, check the specific number directly on your car) | 2112–1148200, 2112–1148200–31 | |
Air flow sensor | 2112-1130010-01GM, square body | |
temperature sensor (Sensors are not interchangeable, check the specific number directly on your car) | 2112–3851010, 2112–3851010–01, 2112–3851010–02 | |
Knock sensor (Sensors are not interchangeable, check the specific number directly on your car) | 2121–3855010, 2121–3855010–01, 2121–3855020 | |
Speed sensor (Sensors are not interchangeable, check the specific number directly on your car) | 2112-3843010, 2112-3843010-20, 2112-3843010-30, 2112-3843010-31, all round connector | |
oxygen sensor | 2121-3850010-11, 2121-3850010-20, type GM AFS-62, AFS-79, Bosch LHS-24 | No |
Injection sensors
What threatens the malfunction of the sensors of the injection system:
- crankshaft position sensor - complete failure of the injection system, the engine does not start;
- mass air flow sensor - an increase in fuel consumption, a significant deterioration in dynamics, problems with starting the engine;
- throttle position sensor - 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 while pedaling "gas", when overheating, power is significantly reduced, detonation appears;
- knock sensor - the engine is very sensitive to the quality of gasoline, an increased tendency to knock.
Features of the electrical equipment of vehicles with distributed fuel injection with feedback
1. Throttle position sensor; 2. Crankshaft position sensor; 3. Coolant temperature sensor; 4. Speed sensor; 5. Adsorber purge valve; 6. Mass air flow sensor; 7. Knock sensor; 8. Oxygen concentration sensor; 9. Blocks of the electronic control unit; 10. Ignition relay; 11. Fuses; 12. Relay for turning on the electric fuel pump; 13. Diagnostic block; 14. Idle speed regulator; 15. Block for connection with the wiring harness of the instrument panel; 16. Board with a control lamp CHECK ENGINE; 17. Mounting block; 18. The electric motor of the fan of the engine cooling system; 19. Electric fuel pump with fuel level sensor; 20. Nozzles; 21. Spark plugs; 22. Ignition module; A. To terminal " " battery; B. To terminal "15/1" ignition switch; C. To the low voltage input of the tachometer on vehicles with "high" panel; K9. Relay for turning on the fan motor