General information and precautions
General information The system is best described by dividing it into four separate sub-systems: air, fuel, engine management (EEC IV system), and ignition.
The air system consists of an air cleaner, connecting air inlet duct, CFI unit, MAP (Manifold Absolute Pressure) sensor, and inlet manifold.
Air is drawn through the air cleaner and inlet duct to the CFI unit. The CFI unit contains an ACT (Air Charge Temperature) sensor and a throttle valve (see illustration).
1.2 Exploded view of the Central Fuel Injection (CFI) unit - 1.4 CFI engine
1 Fuel injector assembly
2 Fuel pressure regulator components
3 Fuel inlet connector
4 Air charge temperature (ACT) sensor 5 Throttle valve control motor 6 Throttle position sensor (TPS) 7 Fuel injector wiring
sensor passes information to the EEC IV module, which uses the information to determine the engine’s fuel requirement. The inlet air then passes the throttle valve into the inlet manifold. Below the throttle valve is a take-off point for the MAP sensor which measures pressure in the manifold, passing this information to the EEC IV module. The EEC IV module uses this information as another factor in determining fuel requirements and ignition timing at full throttle or during ignition key “on” engine “off” conditions. Using the information from the ACT and MAP sensors, the EEC IV module can calculate the mass of air entering the engine and adjust the fuelling and ignition timing accordingly.
The fuel system consists of a fuel pump, fuel filter, and the CFI unit. Power to the system is supplied by the power relay, which has a built-in timer which allows the throttle valve motor to continue to operate after the engine is switched off, preventing the engine from “running on”.
The fuel pump is electric, of roller cell design, and delivers fuel under pressure to the engine. Electric power to the pump is supplied via a relay which is controlled directly by the EEC IV module. The pump contains a nonreturn valve which maintains pressure in the system after the ignition is switched off, to assist starting.
From the fuel pump, the fuel passes through an in-line filter to the CFI unit. A fuel pressure regulator, mounted on the CFI unit maintains fuel pressure to the injector at 1 bar.
Excess fuel is returned to the fuel tank.
The CFI unit, resembling a carburettor, houses the throttle valve, throttle valve control motor, TPS (Throttle Position Sensor), ACT sensor, electronic injector unit, and pressure regulator.
Engine management and emission
The EEC IV (Electronic Engine Control IV) module is a microprocessor-based system containing within its memory the necessary strategy and calibration data. It provides control signals to the output actuators according to the input signals received from the various engine condition sensors. In addition to the sensors mentioned previously, the module also receives data from an engine coolant temperature sensor (ECT), and a speed sender unit (mounted on the speedometer take-off point on the gearbox).
The EEC IV module will calculate the necessary requirements against data stored or programmed into its memory. Accurate control of the engine is thus maintained.
The ignition system consists of a distributor, TFI IV module, ignition coil and HT wiring. These components are more fully described in Chapter 5, Part B.
A knock sensor detects engine detonation, which may occur when using low octane fuel.
Screwed into the cylinder block in such a position as to detect detonation in any of the four cylinders, it passes a signal based on vibration to the EEC IV module. The module analyses the signal and adjusts the ignition timing accordingly.
The function of the catalytic converter is to control and reduce exhaust gas emissions, keeping oxides of nitrogen (NOx), hydrocarbons (HC) and carbon monoxide (CO) to an acceptable level.
The catalyst consists of a ceramic honeycomb coated with platinum and rhodium, housed in a metal exhaust box. The honeycomb design presents a large surface area to the exhaust gas promoting maximum conversion. A HEGO (Heated Exhaust Gas Oxygen) sensor screwed into the exhaust downpipe allows the engine management system to control the air/fuel ratio at the ideal ratio of 14.7:1, which is required for the catalyst to function most effectively.
Note: Following disconnection of the battery, all Keep Alive Memory (KAM) values will be erased from the EEC IV system module memory, which may result in erratic idle, engine surge, hesitation and a general deterioration of driving characteristics.
Warning: Many of the procedures in this Chapter entail the removal of fuel pipes and connections which may result in some fuel spillage. Before carrying out any operation on the fuel system refer to the precautions given in Safety First! at the beginning of this manual and follow them implicitly.
Petrol is a highly dangerous and volatile liquid and the precautions necessary when handling it cannot be overstressed Refer to the precautions given in Part B of this Chapter for models with mechanical fuel injection.
Air cleaner - removal and refitting
Removal 1 On CVH models, disconnect the battery negative lead. 2 Remove the screws from the top of the air cleaner cover (see illustration). 3.2 Air cleaner securing screws (arrowed) 3 Disconn ...
Engine - complete dismantling
OHV engines 1 The need for dismantling will have been dictated by wear or noise in most cases. Although there is no reason why only partial dismantling cannot be carried out to renew such items a ...
Fuel tank - removal and refitting
Note: Refer to the warning at the end of Section 1 before proceeding. Removal 1 The fuel tank will normally only need to be removed if it is severely contaminated with sediment or other substance ...