Ford Sierra Manual

General information and precautions
Fuel and exhaust systems - fuel injection / General information and precautions


General information
2.0 litre SOHC models
The fuel injection system fitted to these models is of the Bosch L-Jetronic type. The system is under the overall control of an EEC IV engine management system which also controls the ignition timing.

Fuel is supplied from the rear-mounted fuel tank by an electric fuel pump mounted next to the tank, via a pressure regulator, to the fuel rail. The fuel rail acts as a reservoir for the four fuel injectors, which inject fuel into the cylinder inlet tracts, upstream of the inlet valves. The fuel injectors receive an electrical pulse once per crankshaft revolution, which operates all four injectors simultaneously. The duration of the electrical pulse determines the quantity of fuel injected, and pulse duration is computed by the EEC IV module on the basis of information received from the various sensors.

Inducted air passes from the air cleaner through a vane type airflow meter before passing to the cylinder inlet tracts via the throttle valve. A flap in the vane airflow meter is deflected in proportion to the airflow; this deflection is converted into an electrical signal and passed to the EEC IV module. An adjustable air bypass channel provides the means of idle mixture adjustment.

A throttle position sensor enables the EEC IV module to compute not only throttle position, but also its rate of change. Extra fuel can thus be provided for acceleration when the throttle is opened suddenly. Information from the throttle position sensor is also used to cut off fuel on the overrun, thus improving fuel economy and reducing exhaust gas emissions.

Idle speed is controlled by a variable orifice solenoid valve which regulates the amount of air bypassing the throttle valve. The valve is controlled by the EEC IV module; there is no provision for adjustment of the idle speed.

Additional sensors inform the EEC IV module of engine coolant and air temperature.

On models fitted with automatic transmission, a sensor registers the change from P or N to a drive position, and causes the idle speed to be adjusted accordingly to compensate for the additional load. Similarly on models fitted with air conditioning, a sensor registers when the compressor clutch is in operation.

A limited operation strategy (LOS) means that the vehicle is still driveable, albeit at reduced power and efficiency, in the event of a failure in the EEC IV module or its sensors.

A fuel filter is incorporated in the fuel supply line to ensure that the fuel supplied to the injectors is clean.

On models produced from mid-1986 onwards, a fuel pump inertia cut-off switch is fitted. This switch breaks the electrical circuit to the fuel pump in the event of an accident or similar impact, cutting off the fuel supply to the engine.

2.0 litre DOHC models
The fuel injection system fitted to these models is under the overall control of an EEC IV engine management system which also controls the ignition timing.

Fuel is supplied from the rear-mounted fuel tank by an electric fuel pump, which is integral with the fuel level sender unit mounted inside the fuel tank. Fuel passes via a fuel filter and a pressure regulator to the fuel rail. The fuel rail acts as a reservoir for the four fuel injectors, which inject fuel into the cylinder inlet tracts, upstream of the inlet valves. The fuel injectors are operated in pairs by electrical pulses supplied by the EEC IV module, and fuel is injected by one pair of injectors every halfrevolution of the crankshaft. The duration of each electrical pulse determines the quantity of fuel injected, and pulse duration is computed by the EEC IV module on the basis of information received from the various sensors.

Inducted air passes through the air cleaner, and through a plenum chamber, before passing on to the cylinder inlet tracts via the throttle valve and inlet manifold. The volume of air entering the engine is calculated by the EEC IV module from information supplied by various sensors. These sensors include an air charge temperature sensor mounted in the inlet manifold, which measures the temperature of the air entering the engine; a manifold absolute pressure (MAP) sensor, which measures the pressure of the air entering the engine; a throttle position sensor; and a crankshaft speed/position sensor, which supplies information on engine speed and provides a timing reference.

Additional sensors inform the EEC IV module of fuel temperature, engine coolant temperature, and vehicle speed (from a gearbox-mounted sensor).

Idle speed is controlled by a variable-orifice solenoid valve, which regulates the amount of air bypassing the throttle valve. The valve is controlled by the EEC IV module; there is no provision for direct adjustment of the idle speed.

On models without a catalytic converter, idle mixture adjustment is by means of a potentiometer connected directly to the EEC IV module. On models with a catalytic converter, an exhaust gas oxygen (HEGO) sensor enables the EEC IV module to control the fuel/air mixture to suit the operating parameters of the catalytic converter; no manual mixture adjustment is possible.

On models with a catalytic converter, an evaporative emission control (EVAP) system is fitted. This prevents the release of fuel vapour into the atmosphere. With the ignition switched off, vapours from the fuel tank are fed to a carbon canister, where they are absorbed. When the engine is started, the EEC IV module opens a purge solenoid valve, and the fuel vapours are fed into the inlet manifold and mixed with fresh air. This cleans the carbon filter. A blow-back valve prevents inlet air being forced back into the fuel tank.

A fuel pump inertia switch is fitted. This switch breaks the electrical circuit to the fuel pump in the event of an accident or similar impact, cutting off the fuel supply to the engine.

A limited operation strategy (LOS) means that the vehicle will still be driveable, albeit at reduced power and efficiency, in the event of a failure in the EEC IV module or its sensors.

1.6 and 1.8 litre (R6A type) CVH models The fuel injection system fitted to these models is under the overall control of an EEC IV engine management system which also controls the ignition timing.

Fuel is supplied from the rear-mounted fuel tank by an electric fuel pump which is integral with the fuel level sender unit mounted inside the fuel tank. Fuel passes via a fuel filter to the Central Fuel Injection (CFI) unit. A fuel pressure regulator, mounted on the CFI unit, maintains a constant fuel pressure to the fuel injector. Excess fuel is returned from the regulator to the tank.

The CFI unit, resembling a carburettor, houses the throttle valve, throttle valve control motor, throttle position sensor, air charge temperature sensor, fuel injector, and pressure regulator.

The duration of the electrical pulse supplied to the fuel injector determines the quantity of fuel injected, and pulse duration is computed by the EEC IV module on the basis of information received from the various sensors.

The fuel injector receives a pulse twice per crankshaft revolution under normal operating conditions, and once per crankshaft revolution under engine idle conditions. A ballast resistor is used in the fuel injector control circuit on 1.6 litre engines.

Inlet air passes through the air cleaner into the CFI unit. The volume of air entering the engine is calculated by the EEC IV module from information supplied by various sensors. These sensors include the air charge temperature sensor and throttle position sensor, mounted in the CFI unit; a crankshaft speed/position sensor which supplies information on engine speed; and a manifold absolute pressure (MAP) sensor which measures the pressure of the air entering the engine.

Additional sensors inform the EEC IV module of engine coolant temperature, and vehicle speed (from a gearbox-mounted sensor).

An exhaust gas oxygen (HEGO) sensor enables the EEC IV module to control the fuel/air mixture to suit the operating parameters of the catalytic converter. No manual mixture adjustment is possible.

Idle speed is controlled by a throttle valve control motor, which controls the position of the throttle valve under conditions of idling, deceleration/part-throttle, and engine start-up and shut-down.

On 1.6 litre engines, a pulse-air system is fitted to reduce the exhaust gas emissions during engine warm-up. The system is controlled by a vacuum-operated valve, which is operated by the EEC IV module via a solenoid.

The system introduces air into the exhaust manifold to increase the exhaust gas temperature, which oxidises more of the pollutants, and brings the catalyst up to working temperature more quickly. The system operates until the catalyst reaches operating temperature, when the control solenoid shuts off the system.

On 1.8 litre engines, an exhaust gas recirculation (EGR) system is used to recirculate a small amount of exhaust gas into the inlet manifold. This process lowers the combustion temperature, resulting in a reduction of NOx (oxides of nitrogen) emissions. The EGR system is controlled by the EEC IV module in conjunction with an Electronic Pressure Transducer (EPT) and an Electronic Vacuum Regulator (EVR).

On certain models, an evaporative emission control system may be fitted. This prevents the release of fuel vapour into the atmosphere. With the ignition switched off, vapours from the fuel tank are fed to a carbon canister, where they are absorbed. When the engine is started the EEC IV module opens a purge solenoid valve, and the fuel vapours are fed into the inlet manifold and mixed with fresh air. This cleans the carbon filter. A blowback valve prevents inlet air being forced back into the fuel tank.

A fuel pump inertia switch is fitted. This switch breaks the electrical circuit to the fuel pump in the event of an accident or similar impact cutting off the fuel supply to the engine.

A limited operation strategy (LOS) means that the vehicle will still be driveable, albeit at reduced power and efficiency, in the event of a failure in the EEC IV module or its sensors.

Precautions
Many of the procedures in this Chapter require the removal of fuel lines 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.

Residual pressure will remain in the fuel lines long after the vehicle was last used, therefore extra care must be taken when disconnecting a fuel line hose. Loosen any fuel hose slowly to avoid a sudden release of pressure which may cause fuel spray. As an added precaution place a rag over each union as it is disconnected to catch any fuel which is forcibly expelled.

Certain adjustment points in the fuel system (and elsewhere) are protected by tamperproof caps, plugs or seals. The purpose of such tamperproofing is to discourage, and to detent, adjustment by unqualified operators.

In some EEC countries (though not yet in the UK) it is an offence to drive a vehicle with missing or broken tamperproof seals. Before disturbing a tamperproof seal, satisfy yourself that you will not be breaking local or national anti-pollution regulations by doing so. Fit a new seal when adjustment is complete when this is required by law.

Do not break tamperproof seals on a vehicle which is still under warranty.

Catalytic converter - precautions The catalytic converter is a reliable and simple device which needs no maintenance in itself, but there are some facts of which an owner should be aware if the converter is to function properly for the full service life.

a) DO NOT use leaded petrol in a car equipped with a catalytic converter the lead will coat the precious metals, reducing their converting efficiency and will eventually destroy the converter.

b) Always keep the ignition and fuel systems well-maintained in accordance with the manufacturers schedule, ensure that the air cleaner filter element, the fuel filter (where fitted) and the spark plugs are renewed at the correct interval if the inlet air/fuel mixture is allowed to become too rich due to neglect, the unburned surplus will enter and burn in thecatalytic converter, overheating the element and eventually destroying the converter.

c) If the engine develops a misfire, do not drive the car at all (or at least as little as possible) until the fault is cured - the misfire will allow unburned fuel to enter the converter, which will result in overheating, as noted above.

d) DO NOT push- or tow-start the car - this will soak the catalytic converter in unburned fuel, causing it to overheat when the engine does start - see b) above.

e) DO NOT switch off the ignition at high engine speeds - if the ignition is switched off at anything above idle speed, unburned fuel will enter the (very hot) catalytic converter, with the possible risk of igniting on the element and damaging the converter.

f) DO NOT use fuel or engine oil additives - these may contain substances harmful to the catalytic converter.

g) DO NOT continue to use the car if the engine burns oil to the extent of leaving a visible trail of blue smoke - the unburned carbon deposits will clog the converter passages and reduce the efficiency; in severe cases the element will overheat.

h) Remember that the catalytic converter operates at very high temperatures - hence the heat shields on the cars underbody and the casing will become hot enough to ignite combustible materials which brush against it - DO NOT, therefore, park the car in dry undergrowth, over long grass or piles of dead leaves.

i) Remember that the catalytic converter is FRAGILE, do not strike it with tools during servicing work, take great care when working on the exhaust system, ensure that the converter is well clear of any jacks or other lifting gear used to raise the car and do not drive the car over rough ground, road humps, etc., in such a way as to ground the exhaust system.

j) In some cases, particularly when the car is new and/or is used for stop/start driving, a sulphurous smell (like that of rotten eggs) may be noticed from the exhaust. This is common to many catalytic converterequipped cars and seems to be due to the small amount of sulphur found in some petrols reacting with hydrogen in the exhaust to produce hydrogen sulphide (H2S) gas; while this gas is toxic, it is not produced in sufficient amounts to be a problem. Once the car has covered a few thousand miles the problem should disappear - in the meanwhile a change of driving style or of the brand of petrol used may effect a solution.

k) The catalytic converter, used on a wellmaintained and well-driven car, should last for between 50 000 and 100 000 miles - from this point on, careful checks should be made at all specified service intervals of the CO level to ensure that the converter is still operating efficiently - if the converter is no longer effective it must be renewed.

EEC IV module - warning
Following disconnection of the battery, the information stored in the EEC IV module memory will be erased. After reconnecting the battery, the engine should be allowed to idle for three minutes. Once the engine has reached normal operating temperature, the idle speed should be increased to 1200 rpm and maintained for approximately 2 minutes, which will allow the module to re-learn the optimum idle values. It may be necessary to drive the vehicle in order for the module to re-learn the values under load. The module should complete its learning process after approximately 5 miles (8 kilometres) of varied driving.


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