All about Ford Mondeo

Fuel injection system/engine management system - general information
Fuel and exhaust systems / Fuel injection system/engine management system - general information


These models are equipped with a Sequential Electronically-controlled Fuel Injection (SEFI) system. The system is composed of three basic sub-systems: fuel system, air induction system and electronic control system. Note: Refer to illustrations 2.1A and 2.1B of Chapter 6 for further information on the components of the system.

Fuel system
An electric fuel pump located inside the fuel tank supplies fuel under pressure to the fuel rail, which distributes fuel evenly to all injectors. A filter between the fuel pump and the fuel rail protects the components of the system. A pressure regulator controls the system pressure in relation to inlet tract depression. From the fuel rail, fuel is injected into the inlet ports, just above the inlet valves, by four fuel injectors. The system also includes features such as the flushing of fresh (ie, cold) fuel around each injector on start-up, thus improving hot starts.

The amount of fuel supplied by the injectors is precisely controlled by an Electronic Control Unit (ECU). The ECU uses the signals derived from the engine speed/crankshaft position sensor and the camshaft position sensor, to trigger each injector separately in cylinder firing order (sequential injection), with benefits in terms of better fuel economy and lower exhaust emissions.

Air induction system
The air system consists of an air filter housing, an air mass meter, an intake resonator and plenum chamber, and a throttle housing. The air mass meter is an informationgathering device for the ECU; it uses a УhotwireФ system to send the ECU a constantlyvarying (analogue) voltage signal corresponding to the volume of air passing into the engine. Another sensor in the air mass meter measures intake air temperature. The ECU uses these signals to calculate the mass of air entering the engine.

The throttle valve inside the throttle housing is controlled by the driver, through the accelerator pedal. As the valve opens, the amount of air that can pass through the system increases. The throttle potentiometer opens further, the air mass meterТs signal alters, and the ECU opens each injector for a longer duration, to increase the amount of fuel delivered to the inlet ports.

Electronic control system The ECU controls the fuel injection system, as well as the other sub-systems which make up the entire engine management system. It receives signals from a number of information sensors, which monitor such variables as intake air mass and temperature, coolant temperature, engine speed and position, acceleration/deceleration, and exhaust gas oxygen content. These signals help the ECU determine the injection duration necessary for the optimum air/fuel ratio. These sensors and associated ECU-controlled relays are located throughout the engine compartment. For further information regarding the ECU and its control of the engine management system, see Chapter 6.

Idle speed and mixture
adjustment - general
Both the idle speed and mixture are under the control of the ECU, and cannot be adjusted. Not only can they not be adjusted, they cannot even be checked, except with the use of special diagnostic equipment (see Chapter 6) - this makes it a task for a Ford dealer service department. Do not attempt to УadjustФ these settings in any way without such equipment.

If the idle speed and mixture are thought to be incorrect, take the vehicle to a Ford dealer for the complete system to be tested.

On models equipped with a heated windscreen, an idle-increase solenoid valve is fitted, which raises the idle speed to compensate for the increased load on the engine when the heated windscreen is switched on. When the valve is open, air from the plenum chamber bypasses the throttle housing and idle speed control valve, passing directly into the inlet manifold through the union on its left-hand end. The system is active only for the four minutes that the heated windscreen circuit is live, and is supplementary to the main (ECU-controlled) idle speed regulation.


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