General description
1. All models with E-series engines and some models with F3P engines are equipped with a central fuel injection system. Differences in systems depending on the engine are indicated in Specifications (see illustrations).
6.1a. Location of major components of the central fuel injection system - E-series engine: 1 - Processor unit and relay; 2 - Intake manifold pressure sensor; 3 - Air filter; 4 - Solenoid valve of the fuel vapor extraction system; 5 - Ignition module; 6 - Battery; 7 - Engine speed and flywheel position sensor; 8 - Throttle body; 9 - Canister for fuel vapor extraction system.
6.1b. Schematic layout of the components of the central fuel injection system: 1 - Coolant temperature sensor; 2 - Knock sensor (where is it installed); 3 - Flywheel position/speed sensor; 4 - Nozzle; 5 - Air temperature sensor; 6 - Throttle potentiometer; 7 - Idle speed drive motor; 8 - Throttle body; 9 - Intake manifold pressure sensor; 10 - Processor unit; 11 - Ignition module; 12 - Vacuum valve; 13 - Solenoid valve of the fuel vapor extraction system; 14 - Fuel vapor extraction system canister; 15 - Fuel filter; 16 - Fuel tank; 17 - Fuel pump; 18 - Oxygen sensor; 19 - One-way valve; 20 - Catalytic converter; C1 - Limiter; C2 - Limiter; SZ - Limiter; C4 - Limiter.
2. The system is something between a conventional carburetor and an electronic distributed fuel injection system(see illustration).
6.2. Throttle Body Components - Central Fuel Injection System: 1 - Fuel pressure regulator; 2 - Air temperature sensor; 3 - Nozzle; 4 - Lower half of the body; 5 - Floating throttle valve; 6 - Upper half of the body.
As with a carburetor, fuel is metered and sprayed in the throttle body, and then the fuel-air mixture is distributed through the intake manifold to the cylinders. As with any modern gasoline injection system, fuel dosage is controlled by a processor unit that receives information from various sensors. The processor also controls idle speed, emission and ignition systems.
3. The main advantage of the central fuel injection system over the carburetor is that the injection system allows for much more precise control of the ratio of mixture components in all engine operating modes. This control is necessary to maintain the minimum level of harmful emissions in the exhaust gases and for the proper functioning of the catalytic converter. Additional advantages from the driver's point of view include lower fuel consumption and better vehicle control when the engine is running cold.
4. The operation of the system can be better understood if it is divided into two parts: the fuel supply and the control system.
Fuel supply
5. The fuel supply subsystem consists of an electric fuel pump immersed in the tank, a fuel filter, a fuel pressure regulator and a fuel injector. The last two components are mounted in the throttle body.
6. Fuel from the pump passes through the filter to the throttle body, where it enters the pressure regulator. The regulator maintains a constant pressure in the injector, relative to the pressure in the throttle body above the throttle valve. Excess fuel is returned to the tank. This way, the fuel circulates continuously while the pump is running, preventing the formation of vapor locks.
7. The fuel injector consists of a needle that is opened by an electromagnet and closed by a spring. The electromagnet is controlled by the injection system processor unit. When the valve is open, fuel is sprayed onto the throttle plate. Due to the constant relative pressure, the amount of fuel injected depends only on the opening time of the injector valve.
8. The supply voltage of the fuel pump is supplied through a relay controlled by the processor unit of the injection system. The pump is only on when the engine or starter is running. Some procedures require the pump to run when the engine is off; to do this, short-circuit the two terminals in the relay socket (see Chapter 8).
Control
9. The control subsystem consists of the injection system processor unit and associated sensors and drives. As mentioned earlier, the processor also controls the emission and ignition systems.
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10. The processor unit is located in the engine compartment, in the right air intake box. (On models with air conditioning, the unit is located in the passenger compartment, under the glove compartment.) The unit receives signals from sensors that monitor the following parameters:
- Coolant temperature.
- Inlet air temperature.
- Engine speed (flywheel sensor).
- Speed of movement (speedometer cable sensor) - not on all models.
- Suction manifold pressure.
- Status "no load" (idle speed sensor).
- Throttle position (potentiometer).
- Oxygen in the exhaust gas (oxygen sensor).
11. On some E7J (1390 cm³) and F3P engines, the processor also receives signals from the knock sensor, which is part of the ignition system and is described in Section 5C. The oxygen sensor is part of the exhaust gas aftertreatment system and is described in detail in Part E of this Section.
12. The output signals from the processor unit control the following components:
- Fuel pump (via relay).
- Fuel injector.
- Idle speed drive motor.
- Solenoid valve of the fuel vapor extraction system.
- Ignition amplifier control unit.
13. The processor processes information from various sensors, determining the amount of fuel that should be injected for a particular engine operating mode at any given time. For this purpose, the intake air volume is calculated based on engine speed and throttle position information, with correction for intake air temperature. At maximum load and during warm-up, additional enrichment is provided. Correction is also performed when the battery voltage changes.
14. In no-load mode (the throttle lever presses the idle speed sensor), the processor stops fuel injection at engine speeds above idle. At idle, the engine speed is controlled by the computer, which sends a signal to the idle drive motor built into the throttle body. The engine opens or closes the throttle valve, constantly maintaining the idle speed regardless of engine temperature or additional load (generator, power steering pump, etc.). There is no need to periodically adjust the idle speed or mixture, even to compensate for engine wear. The system also has automatic adjustment to altitude.
15. When the engine stops, the idle mode drive motor first completely closes the throttle valve, then opens it again to the position ready for the next start.
16. All later models are equipped with an inertia fuel cut-off switch (see Chapter 14), which interrupts the fuel supply in the event of a vehicle collision. The engine cannot be started if the system is activated. The switch needs to be reset.
Troubleshooting
17. In the event of a malfunction, limited diagnostics are available to the car owner. Renault technicians use specialized equipment that allows them to quickly and accurately identify faults. First, it is necessary to inspect the fuel filter, check the condition of the connectors and vacuum hoses. Also remember that improper adjustment of the throttle cable can affect the operation of the fuel injection system, especially at idle.
18. If you suspect a fault with one of the sensors or the processor unit, we recommend contacting a Renault dealer or other specialist.