overviewborich.lesnoe.spb.ru/auto/volvo/greenbooks/subsystems.pdf · alternates from high to low at...

OverviewOverviewOverviewOverview

Sensor systemSensor systemSensor systemSensor system Mass air flow (MAF) sensorMass air flow (MAF) sensorMass air flow (MAF) sensorMass air flow (MAF) sensor

The LH2.4 fuel injection system can be divided into five sub-systems:

The control systemThe control systemThe control systemThe control systemregulates fuel and air supply to provide an optimal fuel/air mix and maintain the correct idling speed. The sensor systemThe sensor systemThe sensor systemThe sensor systemprovides information to the control system which is used for optimizing the control process. The fuel distribution systemThe fuel distribution systemThe fuel distribution systemThe fuel distribution systemis controlled by the control system to distribute fuel to the cylinders. The evaporative emission (EVAP) systemThe evaporative emission (EVAP) systemThe evaporative emission (EVAP) systemThe evaporative emission (EVAP) systemdeals with vapor from the fuel tank (not B 204 E/FT/GT). OnOnOnOn----board diagnostic (board diagnostic (board diagnostic (board diagnostic (OBDOBDOBDOBD) system) system) system) system is common for the fuel injection system and ignition system. It has three diagnostic test modes (DTM) to facilitate fault–tracing.

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The mass air flow sensor (MAF) measures the mass of air drawn into the engine. It automatically compensates for air pressure and temperature which affect the density of the air. There is a wire in the mass air flow sensor (MAF) which is heated to a temperature 150°C higher than the temperature of the intake air (IAT). When the mass of air passing this wire increases it is cooled and it requires a higher current to keep the wire at the correct temperature. This current provides a measurement of the air passing the heated wire. When the engine has stopped deposits on the wire are burnt off by electronically heating it to a temperature of 1000 °C for one second. Were deposits allowed to collect the control module would receive false signals which would result in an incorrect fuel mixture. The Mass air flow (MAF) sensor on B200 G, B204 E, B230 G, B234 G and B204 GT engines have an adjustment screw for setting CO when

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Engine temperature sensorEngine temperature sensorEngine temperature sensorEngine temperature sensor

Exhaust gas temperature sensor (B 204 FT/GT)Exhaust gas temperature sensor (B 204 FT/GT)Exhaust gas temperature sensor (B 204 FT/GT)Exhaust gas temperature sensor (B 204 FT/GT)

Throttle position switch (TP switch)Throttle position switch (TP switch)Throttle position switch (TP switch)Throttle position switch (TP switch)

Heated oxygen sensor (HO2S)Heated oxygen sensor (HO2S)Heated oxygen sensor (HO2S)Heated oxygen sensor (HO2S)

the engine is idling. This has been omitted on the other engines as the oxygen sensor (O2S) control is adaptive throughout its range.

Sends signals to the control module so that it can control injection time and idle speed in relation to engine temperature. It is mounted in the cylinder head and cooled by engine coolant.

The exhaust gas temperature sensor (EGTC) consists of a thermal element in the exhaust manifold before the turbocharger (TC) unit. This senses the exhaust temperature and sends a signal to the fuel injection system control module, which gradually increases the injection period when the exhaust temperature reach a critical level (approximately 950 °C). This contributes to a lower combustion temperature which in turn reduces the exhaust gas temperature, after which the increased fuel supply stops when the exhaust gas temperature has reached a normal level.

Sends signals to the fuel system and distributor ignition (DI system) control module that the throttle is closed (CTP) or wide open (WOT). The B204 FT/GT engine has a throttle position (TP) switch which also has a potentiometer that provides the turbocharger (TC) control system with information on the throttle angle. Turbocharger (TC) models do not use the full load switch.

Normally 14.7 kg air to 1 kg fuel is given as the ideal mixture for complete combustion. This mixture is called lambda = 1 (λ= 1). The

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ThreeThreeThreeThree----way catalytic converter (TWC)way catalytic converter (TWC)way catalytic converter (TWC)way catalytic converter (TWC)

mixture can be gauged by measuring the oxygen content of the exhaust gases after combustion by using a heated oxygen sensor (HO2S).

The heated oxygen sensor (HO2S) produces a voltage signal proportional to the oxygen content in the exhaust gases. This signal alternates from high to low at the ideal mixture of 14.7 kg air/ 1 kg fuel. A rich mixture produces a high voltage while a weak mixture produces a low voltage. The voltage varies between 0.1–0.9 V. The control module's calculations for the amount of fuel to be injected are continuously related to this signal so as to achieve the ideal mixture, λ= 1. The heated oxygen sensor (HO2S) only operates above a certain temperature, approximately 285°C. It is electrically heated so that it reaches its operating temperature quickly. When the ignition is switched on a current is applied to a PTC resistor (PTC=Positive Temperature Coefficient), the resistance of which increases with temperature. This provides a short warm-up time and keeps the sensor at the correct operating temperature when the exhaust gas temperature is low. In engines without a three-way catalytic converter (TWC) (B 230 GT, B 204 GT), i.e engines for markets where unleaded gasoline is not fully available, a heated oxygen sensor (HO2S) which can withstand leaded fuel must be used. However, this heated oxygen sensor (HO2S) has a limited lifespan and must be replaced regularly.

The three-way catalytic converter (TWC) converts 90–95 % of the harmful substances in the exhaust gases to non-toxic ones substances. The three-way catalytic converter (TWC) is of

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Control systemControl systemControl systemControl system Control moduleControl moduleControl moduleControl module

the three-way type and cleans by: Oxidising unburned hydrocarbons (HC) to water vapour (H2O) and carbon dioxide (CO2) Oxidising carbon monoxide (CO) to carbon dioxide (CO2) Reducing nitrogen oxides (NOx) to nitrogen gas (N2).

If the three-way catalytic converter (TWC) is to work properly the heated oxygen sensor (HO2S) must be producing the correct signal so that all the fuel is burnt before being released in the exhaust gases. If this is not done the three-way catalytic converter (TWC) will be damaged by the excessive temperatures generated.

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The control module is located in front of the panel in front of the right door post. It contains a micro processor which retains signals from the different sensors. It determines via the cable how many milliseconds per revolution the injectors should be open. It controls the idle air control valve (IAC valve) so that the correct idle speed is obtained and also controls other functions, for example the cold start injector and fuel pumps. An important function is communicating with the data link connector (DLC) for fault-tracing. The control module is adaptive - it adapts its calculations to values as it learns them.

DEFAULT-ENTITYWhen starting&/emph; a special program is run which gives two injections per revolution. At very low engine temperatures (below approximately –16 °C) the cold start valve is also engaged, if it is fitted on the particular engine. The injection period increases DEFAULT-ENTITYduring acceleration&/emph;. DEFAULT-ENTITYKnock enrichment&/emph; (does not apply to B 204 FT/GT, B 230 F) occurs when the distributor ignition (DI system) knock controller retards all cylinders a number of degrees but knocking still occurs. When

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Idle air control (IAC) valveIdle air control (IAC) valveIdle air control (IAC) valveIdle air control (IAC) valve

knocking, which gives high combustion temperatures, the control module increases fuel quantity. This lowers the combustion temperature which in turn decreases the chance of knocking. DEFAULT-ENTITYThe choke function&/emph; operates up to an engine temperature of approximately 60 °C. Under normal driving conditions the injection time is controlled by the signal from the mass air flow sensor (MAF) and the heated oxygen sensor (HO2S). DEFAULT-ENTITYAt full load&/emph; the fuel/air mixture is enriched so that the engine produces maximum power and to reduce the heat burden on the engine and the three-way catalytic converter (TWC).

DEFAULT-ENTITYOver-revving&/emph; is prevented by an engine speed (RPM) limiter shutting down the injectors. DEFAULT-ENTITYWhen decelerating&/emph; (throttle position switch (TP switch) in idle mode) the fuel injection is shut down at engine speeds (RPM) over approximately 2000 rpm. It is reintroduced at approximately 1400-2000 rpm, depending on engine temperature. This function has been gradually omitted on the B 230 FB engine during the –92 model year. The control module runs an DEFAULT-ENTITYemergency program&/emph; (limp home mode), if certain signals are faulty or missing. The signals a determined value which means that the car can be driven to the workshop.

The idle air control (IAC) valve has two roles. It must keep the engine idle speed constant no matter what the load from the automatic transmission, air conditioning (A/C), engine cooling fan (FC), power steering or generator (GEN). It must also supply air to the engine when the engine is braking the car so that the negative pressure in the intake manifold is kept at a permissible level. The valve is a only active and controlled by the control module when the

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Adaptive idle air trimAdaptive idle air trimAdaptive idle air trimAdaptive idle air trim

idling switch is closed, when the idling switch is open the valve takes an open standby mode and still receives signals from the control module.

To provide the idle air control valve (IAC valve) the proper opening angle the control module utilizes information about engine speed (RPM), engine temperature and intake air mass. The control module also uses data from the speedometer to find out if the car is moving or not, the engine cooling fan (FC) at high-speed (B 230 F/FT, B 234 model year 92-, B 204 FT/GT), from the air conditioning (A/C) control when the air conditioning (A/C) is switched on and from the air conditioning (A/C) compressor when it starts and stops. On cars with automatic transmission the idle control also receives information about the gear engaged. Idle speed is mainly determined by engine temperature. However, depending on car model, idle speed can be influenced by the air conditioning (A/C) being turned on, the engine cooling fan (FC) switching to high speed, or a gear being engaged (cars with automatic transmission). In the idle air trim function (control module) are included safety functions will stop the idle speed going too high by sending a signal to the idle air control (IAC) valve which is the equivalent of opening angle=0. In this condition it is as if the valve is without power when it is pulled towards the mechanical stop by a spring. In both cases the engine idle speed is approximately 1000-2000 rpm. This safety function is often triggered if there is too great a flow over the throttle disc (throttle incorrectly adjusted).

In time wear and coatings will affect the throttle so that it allows more or less air to pass through. Instead of adjusting from a preprogrammed value the control module gives a signal based on information received during earlier operation. This signal opens the idle air control valve (IAC valve) by exactly the right

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Adaptive heated oxygen sensor controlAdaptive heated oxygen sensor controlAdaptive heated oxygen sensor controlAdaptive heated oxygen sensor control

System relaySystem relaySystem relaySystem relay

FusesFusesFusesFuses

amount to keep the engine idling at the correct speed.

Using the adaptive fuel trim the control module can adapt injection times to compensate for engine wear, small air leaks, clogged injectors and the like allowing the heated oxygen sensor (HO2S) to control engine functions optimally. The long-term fuel trim has two types of function, additive and multiplicative compensation. Additive compensation acts on injection time quickly at low engine speeds (RPM), for example when the engine is idling. Additive control corresponds to the basic CO setting which is carried out by a potentiometer in other systems. Multiplicative control generally acts on slow changes. The ability of the oxygen sensor (O2S) to compensate for large faults is limited. The control module stores the diagnostic trouble code (DTC) 2-3-1 or 2–3–2 depending on whether it is an additive or multiplicative compensation limit that has been exceeded.

The system relay is controlled by the control module and powers the fuel pumps (FP), the injectors, the idle air control valve (IAC valve), the cold start valve, the mass air flow sensor (MAF), the oxygen sensor (O2S) pre-heat resistor and some of the control module functions.

The system relay is protected by a 25A fuse and the fuel pump (FP) and heated oxygen sensor (HO2S) pre-heat resistor by a 15 A fuse.

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Controlling the engine cooling fan (FC) (Does not apply to B204FT)Controlling the engine cooling fan (FC) (Does not apply to B204FT)Controlling the engine cooling fan (FC) (Does not apply to B204FT)Controlling the engine cooling fan (FC) (Does not apply to B204FT)

(Applies to all 1992- models with air conditioning (A/C)) The engine cooling fan (FC) is controlled via a low-speed relay and a high-speed relay based on information on engine coolant temperature (ECT), car speed and air conditioning (A/C) system pressure.

The engine cooling fan operates at low-speed if: Coolant temperature is above 102°C. The engine cooling fan operates at low-speed if: The air conditioning (A/C) system pressure is greater than 17 bar on the high pressure side and the speed of the car is below 100 kph. The engine cooling fan operates at high-speed if: Engine coolant temperature (ECT) is above 115°C or the pressure in the air conditioning (A/C) system high pressure side exceeds 22 bar.

The engine cooling fan always starts at low-speed for approximately 15 seconds before it can operate at high-speed. It always runs at low-speed for 5 seconds when it stops operating at high- speed. If the ignition is turned off when the fan is operating at high-speed it will continue at low-speed for 5 seconds. So as not to overload the engine there is a delay which prevents the fan from starting for 9 seconds after the engine has been started, no matter what the engine temperature or air conditioning (A/C) system pressure. To cool the engine and avoid overheating, the engine cooling fan will continue to operate at

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Fuel distribution systemFuel distribution systemFuel distribution systemFuel distribution system

Fuel tank pumpFuel tank pumpFuel tank pumpFuel tank pump

Fuel pump (FP)Fuel pump (FP)Fuel pump (FP)Fuel pump (FP)

Fuel filterFuel filterFuel filterFuel filter

low-speed for three minutes if engine temperature exceeds 105°C when the ignition is switched off.

The fuel distribution system consists of: AAAA Fuel filter. BBBB Fuel pump (FP). CCCC Tank pump.

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An electrical impeller pump maintains pressure in the line to the main fuel pump (FP) to counteract the negative pressure in the main pump's low side. The tank pump has a coarse strainer filter.

An electrical roller pump which is cooled by the fuel running through it. It has a non-return valve and overflow valve which opens if the pressure becomes to great. Both tank and fuel pumps (FP) are connected and operate when the starter motor operates or when the engine is running. If the engine stalls and the ignition is on the control module cuts the power to the pumps so as to minimise the risk of fire in the event of an accident.

The fuel filter has a paper filter with an additional strainer to catch particles which could drop off the paper filter.

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Fuel railFuel railFuel railFuel rail

Pressure regulatorPressure regulatorPressure regulatorPressure regulator

InjectorsInjectorsInjectorsInjectors

Cold start valve (2 valve engines)Cold start valve (2 valve engines)Cold start valve (2 valve engines)Cold start valve (2 valve engines)

The fuel inlet line, pressure regulator, injectors and cold start injector are connected to the fuel rail.

Controls the fuel pressure in the injector lines. A vacuum line connected to the engine intake manifold maintains the fuel pressure at a constant 300 kPa above the pressure in the intake manifold. The pressure drop over the injectors is thus always constant, irrespective of throttle position (TP). The quantity of fuel injected is therefore only dependent on how long the injectors are open. Surplus fuel is returned to the fuel tank via a return pipe.

These are fitted with a solenoid and fuel metering needle which open and close a nozzle. The control module grounds the injectors via an auxiliary relay for a certain time so that the valves open injecting atomised fuel. Injection occurs twice per revolution when the starter motor is operating (engine cold), and once per revolution when the engine is running. Injection takes place in the intake manifold near the intake valves.

The cold start function was dropped from certain engines during 1991 and was dropped completely for the 1992 models. When the engine is being started from cold a great deal of fuel condenses into droplets on

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Evaporative emission (EVAP)Evaporative emission (EVAP)Evaporative emission (EVAP)Evaporative emission (EVAP)----systemsystemsystemsystem

cold surfaces. A separate cold start valve improves cold starting characteristics. It is located further from the engine than the injectors and supplies fuel in a highly vaporised form instead of in droplet form. The valve is engaged a approximately –16 °C and at engine speeds below approximately 900 rpm. It is disengaged completely when the engine speed (RPM) has exceeded this boundary value once.

Evaporative emission (EVAP) stands for Evaporative emission control system and is a system which deals with the gases evaporating from the fuel in the fuel tank, preventing them from entering the atmosphere. Fuel vapour pass through a system of hoses from the fuel tank filler opening through a roll-over valve into a carbon filter canister. This absorbs the fuel vapour and prevents it from venting into the atmosphere. Charcoal filter, EVAP canisterCharcoal filter, EVAP canisterCharcoal filter, EVAP canisterCharcoal filter, EVAP canister Fuel vapour from the tank are led into the top of the carbon filter and bonded to active carbon. Air is pushed out through a channel in the base of the canister. Depending on the temperature etc., the carbon filter can bind about 90 g of fuel. RollRollRollRoll––––over valveover valveover valveover valve This closes when the car tilts sideways more than 45 degrees and prevents fuel leaking out in the event of an accident. Evaporative emission (EVAP) valve (vacuum)Evaporative emission (EVAP) valve (vacuum)Evaporative emission (EVAP) valve (vacuum)Evaporative emission (EVAP) valve (vacuum) This is located at the top of the carbon filter and is closed when the engine is not running. It is also closed when the engine is idling so it does not interfere with the automatic idle air control system and the engine idle characteristics. The valve is controlled by a vacuum from the intake manifold which is connected to the positive side of the throttle. When engine load increases the evaporative emission (EVAP) valve opens allowing fuel vapour to flow from the carbon filter to the engine's intake manifold. Air is drawn in at the

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same time through the channel in the base of the filter. Normally the carbon filter is emptied within 15–20 minutes. Evaporative emission (EVAP) valve (electrical)Evaporative emission (EVAP) valve (electrical)Evaporative emission (EVAP) valve (electrical)Evaporative emission (EVAP) valve (electrical) On the B 234 F the evaporative emission (EVAP) vacuum valve has been replaced with an electrically activated valve located between the canister and the engine intake manifold. It works in the same way as the vacuum valve.

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overviewborich.lesnoe.spb.ru/auto/volvo/greenbooks/subsystems.pdf · alternates from high to low at...

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