3356174 - INTRODUCTION - PETROL FUEL INJECTION SYSTEM

CONSTRUCTION SPECIFICATIONS

The Marelli IAW 5NF system (5SF for the Z 16 XEP engine) belongs to the category of systems integrated with:

  • inductive discharge, digital, electronic ignition
  • static advance
  • sequential, phased type electronic injection (1-3-4-2).
1, Fuel tank2, Electric fuel pump3, Multifunction valve4, Safety valve5, Fuel delivery pipe6, Electronic injection/ignition control unit7, Battery8, Ignition switch9, Inertia switch10, Engine compartment junction unit11, Climate control system12, Fuel vapour cut out solenoid valve13, Injection timing sensor14, Activated carbon filter15, Body Computer (diagnostic socket and Fiat CODE signal)16, Temperature/absolute pressure sensor17, Rpm and TDC sensor18, Spark plugs19, Coolant temperature sensor20, Injectors21, Throttle control actuator and throttle position sensor22, Accelerator pedal potetiometer23, Fuel supply manifold24, Air filter25, Ignition coils26, Lambda sensor (pre-catalyzer)27, System failure warning light.28, Rev counter29, Catalytic converter30, Lambda sensor (post-catalyzer)

Operation of the injection/ignition system

In engine idle conditions, the control unit controls:

  • the moment of ignition
  • the air flow rate with the benefit of maintaining smooth engine operation even when environmental and applied load parameters change.
The control unit controls and manages injection so that stoichiometric air/fuel ratio is always within optimum limits.

The system functions are essentially as follows:

  • system self-adaptation
  • self-diagnostics
  • Fiat CODE recognition
  • cold starting check control
  • control of combustion - Lambda sensors
  • detonation control
  • check on enrichment during acceleration
  • fuel cut-off during deceleration
  • fuel vapour recovery
  • restriction of maximum rpm
  • fuel pump control
  • connection with climate control system
  • cylinder position recognition
  • injection time adjustment
  • ignition advance adjustment
  • control and management of idle speed
  • control of cooling fan.

Injection system

The essential conditions to be met by the air-fuel mixture for efficient operation of engines with controlled ignition systems are mainly as follows:

  • the metering (air/fuel ratio) must be kept as close as possible to stoichiometric value to ensure that combustion is as fast as possible avoiding fuel wastage
  • the homogeneity of the mixture, consisting of petrol vapours distributed throughout the air as finely and uniformly as possible.
The injection/ignition system uses an indirect measuring system known as the "SPEED DENSITY-LAMDBA" type in other words the angular rotation speed, density of the intake air and control of the mixture strength.In practice, the system uses the ENGINE SPEED data (rpm) and the AIR DENSITY (pressure and temperature) to measure the quantity of air drawn in by the engine.The quantity of air drawn in by each cylinder, for every engine cycle, also depends on the unit capacity and the volumetric efficiency as well as on the density of the intake air.The density of the air refers to the air drawn in by the engine and calculated according to the absolute pressure and temperature, both measured in the intake manifold.The volumetric efficiency is the parameter relating to the filling coefficient for the cylinders measured on the basis of experiments conducted on the engine for the entire operating range and then stored in the electronic control unit memory.Having established the quantity of intake air, the system must provide the amount of fuel depending on the desired mixture strength.The end of injection impulse or supply timing is stored in a map in the control unit memory and varies according to the engine speed and the pressure in the intake manifold. In practice, it involves processing carried out by the electronic control unit to control the sequential and timed opening of the four injectors, one per cylinder, for the length of time strictly necessary to produce the air/petrol mixture as close as possible to the stoichiometric ratio.The fuel is injected directly into the manifold near the inlet valves at a pressure of around 3.5 bar.Whilst the speed (rpm) and the density of the air (pressure and temperature) are used for measuring the quantity of intake air which, when established, is used for metering the quantity of fuel depending on the desired mixture strength, the other sensors in the system (coolant temperature, throttle valve position, battery voltage) allow the electronic control unit to correct the basic strategy for all engine operating conditions.It is vital for the air/fuel ratio to be close to the stoichiometric value for the correct and prolonged operation of the catalytic silencer and for reducing pollutant emissions.

Ignition system

The ignition circuit is the static, inductive discharge type, i.e. without a HT distributor, with power modules located inside the injection -ignition control unit.On this system there is a coil for each cylinder connected directly to the spark plug.The primary winding for each coil is connected to the power relay (thereby receiving the battery voltage supply) and to the pins of the electronic control unit for earthing.

After the starting stage, the electronic unit manages the basic advance taken from a special map in accordance with:

  • engine rpm
  • absolute pressure value (mbar) measured in the intake manifold.
This advance value is corrected depending on the temperature of the engine coolant and the intake air.

Diagram showing information entering/leaving the control unit

The fuel level and engine oil pressure information reaches the control unit via the CAN line.
1, Engine management control unit2, Battery3, Ignition switch4, Engine control system relay5, Electric fuel pump relay6 , Fuel pump7, Radiator fan relay(s)8, Radiator fan9, Compressor engagement relay10, Compressor11, Injectors12, Spark plugs13, Ignition coils14, Carbon filter scavenging solenoid15, Lambda sensor (pre-catalyzer and post-catalyzer)16, Coolant temperature sensor17, Detonation sensor18, Throttle control actuator and throttle position sensor19, Rpm and TDC sensor20, Air temperature/absolute pressure sensor21, Engine oil pressure switch22, Body computer23, CODE control unit (body computer) (via CAN)24, Diagnostic equipment connection (via CAN)25, Rev counter (via CAN)26, System failure lamp (via CAN)27, Speedometer (via CAN)28, Injection timing sensor29, Accelerator pedal sensor30, Clutch pedal switch31, Coolant temperature sensor32, E.G.R. solenoid valve (for Z16XEP engine only)33, PDA system (for Z16XEP engine only)

Operating strategies

System self-adjustment

The control unit is equipped with a self-adjustment function that is designed to recognize the changes that take place in the engine due to the processes of bedding in and ageing of both the components and the engine itself in time.These changes are memorized in the form of modifications to the basic map and are designed to adapt the operation of the system to the gradual alterations in the engine and the components compared with when they were new.This self-adjustment function also makes it possible to compensate for the inevitable differences in any replacement components (due to production tolerances).The control unit modifies the basic map in relation to engine specifications when new on the basis of an exhaust gas analysis.The self-adjustment parameters are not deleted if the battery is disconnected.

Self-diagnosis

The control unit auto-diagnostic system checks that the system is working properly and signals any irregularities by means of an MIL warning light in the instrument panel with a standardized ideogram and colour laid down by European regulations.This warning light indicates engine management faults and also faults detected by EOBD diagnostic strategies.

The MIL warning light operating (mil) strategy is as follows:

  • with the ignition on, the warning light comes on and remains on until the engine has been started up.
  • The control unit self-diagnostic system checks the signals coming from the sensors comparing them with the permitted limits.

Fault indication during start up:

  • the failure of the warning light to go out when the engine has been started indicates that there is an error memorized in the control unit.

Fault indication during operation:

  • the warning light comes on in flashing mode to indicate possible catalytic converter damage due to misfiring.
  • the warning light comes on in constant mode to indicate the presence of engine management or EOBD RECOVERY diagnostic errors.
From time to time the control unit defines the type of recovery according to the components that are faulty.The recovery parameters are managed by components that are not faulty.

Fiat code recognition

The moment the control unit receives the ignition ON signal it converses with the Body Computer (Fiat CODE function) to obtain the go ahead for starting.The communication takes place via the CAN line that connects the two control units.

Recognition of cylinder position

The engine timing sensor, together with the engine rpm and top dead centre (TDC) signal, allows the control unit to recognise cylinder sequence when implementing phased injection.This signal is produced by a Hall effect sensor, positioned on the tappet cover near the flywheel on the camshaft pulley.

Combustion - lambda sensor check

On EOBD systems the Lambda sensors, all the same type but not interchangeable, are positioned one before (pre) the catalyzer system and one after (post) the catalytzer.The pre-catalyzer sensor determines the control of the mixture strength known as the 1st closed loop for the upstream sensor.The post-catalyzer sensor is used for the fault diagnosis of the catalyzer and for modulating the 1st loop control parameters.The second loop is therefore adaptive to make up for production discrepancies and slight drift that pre-catalyzer sensor responses could experience due to ageing and contamination.This control is known as 2nd loop control (post-catalyzer sensor closed loop).

Operation when cold

In these conditions there is a natural weakening of the mixture as a result of the poor turbulence of the particles of fuel at low temperature, reduced evaporation and strong condensation on the internal walls of the intake manifold, all of which is exacerbated by the increased viscosity of the lubricant oil which, as is known, increases the rolling resistance of the engine mechanical components at low temperatures.The electronic control unit recognizes this condition on the basis of the coolant temperature signal, increasing the basic injection time.

Operation in full load conditions

The full load condition is detected by the control unit by means of the throttle position and absolute pressure values.In full load conditions the basic injection time must be increased to create the maximum power supply produced by the engine.

Operation in deceleration

The engine has two overlapping strategies during this stage:

  • A negative transition strategy to keep the quantity of fuel supplied to the engine at the stoichiometeric level (less pollution). This stage is recognized by the control unit when the throttle position signal goes from a high voltage value to a lower one.
  • A soft accompaniment strategy at low speed (dash-pot) to dampen the variation in torque supplied (reduced engine braking).
Barometric correctionAtmospheric pressure varies according to altitude causing a variation in volumetric efficiency such that requires a correction in the basic mixture strength (injection time).The correction of the injection time depends on the variation in atmospheric pressure and will be automatically updated by the electronic control unit each time the engine is switched off and in certain throttle position and rpm conditions (e.g.: at low speed and with the throttle very open)Cut-off operationThe fuel cut-off strategy is implemented when the control unit recognizes that the throttle valve is in the idle speed and the engine speed = 1350 rpm (variable indicative value).The control unit only enables the cut-off when the engine temperature exceeds 0° C.When the engine speed = 1270 rpm (variable indicative value) and the throttle valve is not in the closed position, the control unit re-enables the engine supply.The cut-off is implemented at very high speeds even if the throttle valve is not completely closed but the pressure in the intake manifold is particularly low (partial cut-off).

Operation in acceleration

In this stage the control unit increases the amount of fuel supplied to the engine (to produce the maximum torque) depending on the signals:

  • throttle position;
  • rpm and T.D.C. signal
The basic injection time is multiplied by a coefficient depending on the temperature of the engine coolant, the ope
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Pda system

A PDA system for petrol engines has been used for the first time on the Z 16 XEP engine. PDA stands for "Port-Deaktivation", in other words excluding the inlet ports.The PDA system offers the following advantages:

  • increase in the EGR rateextension of the compatible EGR engine speed rangeacceleration of the combustion process in the low load range without EGRimprovement in driving stability in the intermediate load range thanks to the high load motionreduction in fuel consumption
Pda system operating principlesThe closing of one of the two inlet ports for each cylinder involves an increase in the charge motion and therefore faster and more stable ignition which is a requirement for a high EGR rate.Thanks to the use of exhaust gas recirculation, the high combustion speed is reduced to allow an excellent compromise in terms ofcombustion noise, the emission of unburnt particles in the exhaust gases, engine knock limits and charge losses.As a result, in addition to a decrease in unburnt particles in the exhaust gases there is also a considerable fuel saving.
Operation of the pda systemThe switching throttles positioned in the filler duct are opened or closed by a jointly controlled rod operated by a vacuum capsule.The switching throttles positioned in the filler duct are opened or closed by a jointly controlled rod operated by a vacuum capsule.The vacuum is produced by the motion of the air inside the air chamber.
After the engine has been started, usually within a few seconds, the vacuum created is sufficient to operate the switching throttles.The vacuum used for moving the switching throttles control rod is metered by the intervention of the adjustment solenoid valve operated by the engine management control unit.When the adjustment solenoid valve is not energized, it opens through the action of the spring, the vacuum capsule is ventilated and the throttles are opened by the force exerted by the springs in the vacuum capsule and in the position sensor.The idle speed adjustment functions that depend on the position of the switching throttles, for example the EGR rate and ignition, are regulated by the engine management control unit.The control unit receives the switching throttle position signal via the position sensor (located on the rear end of the first throttle near the vacuum capsule) which reads the effective position of the actual switching throttles.
The fuel injection takes place by means of new injectors with twin jets; these twin jets supply the filler duct and the turbulence duct respectively.To ensure the washing of the excluded ducts, the switching throttles have a predefined seepage; the filler ducts are therefore never completely closed.The engine management control unit requests the closure of the switching throttles each time this involves advantages in relation to fuel consumption and driving stability; in general, this happens during idling and in the intermediate load range until about halfway load conditions at speeds of 3000 rpm. As a result the air/fuel mixture introduced flows mainly through the turbulence duct.With the switching throttle open, full load conditions and high engine speed, the mixture also flows through the second duct which is optimum for filling.Fault diagnosis of the pda systemThanks to the detection of the effective position of the switching throttles by the position sensor, the operation of the engine is guaranteed without serious limitations even if there are malfunctions in the movement system of the actual throttles.Possible complaints by the customer therefore could refer to irregular operation during idling and in intermediate load conditions with the throttles open or to a loss in power at high speeds with the throttles closed.Malfunctions of the switching throttles are detected via the position sensor by the engine management control unit and are recorded in the fault code memory.These codes can then be read using the diagnostic equipment.

Egr control and adjustment

In relation to the engine parameters (rpm, load, temperature, atmospheric pressure, air temperature) the engine management control unit limits the quantity of fresh air introduced, implementing the partial intake of exhaust gases through the regulation of the opening of the E.G.R. electrical valve.This reduces the emission of nitrogen oxide. The solenoid valve does not depend on the vacuum but may be open or closed in all load conditions.The exhaust gas recirculation valve is fitted with the following components:

  • Solenoid valve: the opening of the solenoid valve is linked to the current for the coils and is regulated by an impulse width modulation signal (PWM) for the engine management control unit. The opposing force required to keep the exhaust gas recirculation valve closed when there is no current is applied by means of a coil spring.Piston potentiometer: this transducer signals the opening extent of the valve to the control unit. The piston potentiometer makes it possible to regulate the position of the solenoid valve with precision.

recovery

Air temperature sensor

If the error is present during starting:

  • it assumes a value of 50 °C
  • the mixture strength self-adjustment is inhibited.

If the error is present in other conditions:

  • the last valid value is memorized and updated depending on the engine temperature.

Detonation sensor

If this sensor is faulty, the engine management control unit implements the most conservative ignition advance maps to safeguard the engine.

Pressure sensor

If the error is present during starting, a value of 1024 mbar is used.During operation the value is calculated on the basis of the parameters supplied by the throttle position and rpm sensors.The mixture strength self-adjustment is inhibited.

Vehicle speed sensor

The last vehicle speed value memorized is used.

Coolant temperature sensor

If there is a fault, the control unit inhibits the mixture strength self-adjustment and idling.Setting the last temperature value measured; if it does not correspond to the operating temperature, the control unit increases it gradually depending on the time since the engine has been started until the theoretical figure of 80°C is reached.In addition, when the ignition key is inserted, the radiator cooling fan is activated permanently at the second speed.

IAW 5NF injection/ignition control unit (5SF for Z 16 XEP engines)

The control unit is fitted in the engine compartment on the intake manifold chamber and is capable of withstanding high temperatures.It is a digital type unit with a microprocessor featuring a high calculation capacity and is accurate, reliable, versatile, with low energy consumption and is maintenance-free.The task of the electronic unit is to process the signals coming from the various sensors through the application of software algorithms and to control the operation of the actuators (in particular the injectors, ignition coils and idle actuator) in order to ensure the best possible operation of the engine.The adoption of the Fiat CODE means that control units cannot be swapped between vehicles.

Pin out

The diagram below shows the control unit pin out.
Engine Side Connector1 Coil 4 control2 EGR valve control3 Coil 3 control4 12V from main relay5 Engine Earth or Battery6 Engine Earth or Battery7 Pressure/Timing Sensors Earth8 Not Connected9 Rpm Sensor Positive10 Not Connected11 PDA valve control12 Not Connected13 5V power supply for Pressure/Timing and PDA/EGR potentioemter14 Not Connected15 5V Drive By Wire power supply16 EGR Position17 Coil 1 Control (1 - 4)18 Not Connected19 Coil 2 Control (2 -3)20 Not Connected21 Engine Earth or Battery22 Engine Earth or Battery23 Rpm Sensor Negative24 Timing Sensor Signal25 Not Connected26 Not Connected27 Not Connected28 Not Connected29 Not Connected30 Throttle 2 Sensor Signal31 Pressure Sensor Signal32 Upstream Lambda Heater Control33 Cylinder 4 Injector Control34 Cylinder 2 Injector Control35 Throttle 1 Sensor Earth36 Coolant Temperature Sensor and PDA/EGR potentiometer GND37 Not Connected38 Not Connected39 Not Connected40 Not Connected41 Detonation Sensor Positive42 Downstream Lambda Sensor Signal (+)43 Upstream Lambda Sensor Signal (+)44 Throttle 1 Sensor Signal45 Coolant Temperature Signal46 Not Connected47 Not Connected48 Detonation Sensor Negative49 Cylinder 3 Injector Control50 Cylinder 1 Injector Control51 Canister Scrubbing Solenoid Valve Control52 DBW Motor Negative Cotnrol53 Not Connected54 Not Connected55 Not Connected56 Not Connected57 DBW Motor Positive Cotnrol58 Downstream Lambda Sensor Negative Signal59 Not Connected60 Upstream Lambda Sensor Negative Signal61 Not Connected62 PDA Position63 Air Temperature Signal64 Downstream Lambda Sensor HeaterVehicle Side Connector1 Not Connected2 Pedal 1 Sensor Power Supply3 Pedal 2 Sensor Power Supply4 Not Connected5 Linear Pressure Sensor Input6 Not Connected7 Oil Pressure Signal 18 Not Connected9 Not Connected10 Serial Line K11 Immobilizer Line12 Key-on and Ignition-Controlled Power Supply (DBW)13 Pump Relay Feed ( HS )14 Not Connected15 Pedal 2 sensor earth16 12V Direct Battery17 Input for Cruise ( Resume )18 Not connected19 Oil Pressure Signal 220 CAN High Speed Line Repetition ( - )21 Input for Cruise Control22 Not connected23 Not connected24 Not connected25 Not connected26 Air Conditioning Engagement Request27 Not connected28 Not connected29 Key-on and Ignition-Controlled Power Supply (DBW)30 Not connected31 Not connected32 Not connected33 Cruise Control Engagement Input34 Brake Pedal Switch35 Brake Pedal Light36 CAN High Speed Line ( - )37 Not connected38 Not connected39 Not connected40 Accelerator Pedal 2 Potentiometer Signal41 Input for Cruise ( DEC )42 Accelerator Pedal 1 Potentiometer Signal43 Not connected44 Not Connected45 Not connected46 Pedal 1 sensor earth47 Not connected48 Not connected49 Vehicle Speed (signal managed at CAN)50 Clutch Switch Signal51 CAN High Speed Line Repetition ( + )52 CAN High Speed Line ( + )53 Not Connected54 Not Connected55 Low speed Fan Engagement Control56 Engine coolant overheating warning light (managed on CAN line)57 Not Connected58 MIL/EOBD Failure Light59 High Speed Fan Engagement Control60 Not Connected61 Not Connected62 Main Relay Feed63 Rev Counter Signal (managed on CAN line)64 Air Conditioning Engagment Control

Injectors

Specifications

The injectors are the miniature type (Pico) with a 12 V supply and an internal resistance of 13.8 - 15.2 ohm at 20°C.The injectors are fastened by the manifold which presses against them in their seats in the intake manifold ducts, whilst the two fluorine rubber seals (1) and (2) provide a seal on the inlet manifold and the fuel manifold.The fuel supply takes place from the top (3) of the injector whose body contains the winding (4) connected to the terminals (5) of the electrical connector (6).
Do not apply stress to the injector manifold during the removing-refitting operations as it could adversely affect its operation.

Operation

The jet of fuel comes out of the injector at an absolute pressure of 3.5 bar through the returnless system atomizing immediately.The injector control logic is the phased sequential type, i.e. the four injectors are operated in accordance with the inlet stages.

FUEL MANIFOLD

Specifications

The fuel manifold is fastened to the inner part of the intake manifold and its function is to transfer the fuel to the injectors.In addition to the seats for the injectors there is a rapid connector on the fuel manifold for connection with the fuel supply pipe and a connector for checking the fuel supply pressure.

Engine COOLANT temperature sensor

Specifications

This is fitted to the thermostat cup and detects coolant temperature by means of an NTC thermistor with negative resistance coefficient.Electrical properties
°CO
-2015971
-109620
05975
103816
202502
252044
301679
401152
50807
60576
70418
80309
90231
100176

Operation

The reference voltage is 5V for the NTC element for the injection system. Because the control unit input circuit is designed as a voltage divider, this voltage is distributed between a resistance present in the control unit and the sensor NTC resistance.The control unit is therefore able to assess sensor resistance changes via changes in the voltage and thus obtain temperature information.

Composition

The sensor components are:
1, N.T.C. resistance2, Sensor casing3, Electrical connector The engine coolant temperature sensor is fastened to the thermostat unit.The location on the Z16XEP engine is illustrated in the diagram below.

Detonation sensor

Specifications

The piezoresistive type detonation sensor is fitted on the crankcase between and measures the intensity of vibrations caused by knock in the combustion chambers.This phenomenon has mechanical repercussions on a piezoelectric crystal that sends a signal to the control unit which, on the basis of this signal, reduces the ignition advance until the phenomenon disappears.The control unit restores the advance gradually until the optimum operating value is reached.

Operation

The molecules of a quartz crystal are electrically polarised.In rest condition (A), the molecules do not display any particular orientation.When the quartz crystal is subject to pressure or impact (B), the degree of alignmnent is directly proportional to the pressure acting on the crystal.This orientation generates a voltage at the crystal terminals.
A, Rest positionB, Position under pressureElectrical propertiesresistance: 532-588 ohm at 20°C. The detonation sensor is fastened to the cylinder block/crankcase near the alternator.The location on the Z16XEP engine is illustrated in the diagram below.

Rpm sensor

Specifications

It is fitted on the cylinder block/crankcase facing the flywheel on the crankshaft pulley.It is inductive type, i.e. its operation is determined by magnetic field changes generated by the teeth passing in front of the phonic wheel (602 teeth).

The injection control unit uses the rpm signal for:

  • determining the rotation speed of the crankshaft
  • determining the angular crankshaft position.

Composition

The sensor takes the form of a tubular case (1) containing a permanent magnet (3) and an electrical winding (2).

Operation

Due to the passage of the phonic wheel teeth, the magnetic flux set up by magnet (3) undergoes fluctuations due to changes in the gap.These fluctuations set up an electromotive force in winding (2) and a voltage is set up at the terminals that is alternatively positive (tooth facing sensor) and negative (gap facing sensor).The rpm sensor peak output voltage depends, all else being equal, on the distance between the sensor and the phonic wheel teeth (gap).There are sixty teeth on the flywheel, with two having been removed to produce a reference: the passing of the wheel therefore corresponds to an angle of 6° (360° divided by 60 teeth).The synchronism point is recognised at the end of the first tooth following the gap left by the two missing teeth: when this passes beneath the sensor, the crankshaft is located with piston pair 1-4 at 114° before TDC.
1, Sensor2, Output signal3, Signal corresponding to two missing teeth4, Crankshaft pulley with flywheelElectrical properties:resistance: 1134-1386 ohm at 20°C.The recommended distance (gap) between the end of the sensor and the flywheel for obtaining correct signals should be 0.5 - 1.5 mm.The rpm sensor is fastened to the cylinder block/crankcase near the oil filter. The location on the Z16XEP engine is illustrated in the diagram below.

Accelerator pedal potentiometer

Specifications _ -the accelerator pedal is equipped with two built-in potentiometers: *- a main one *- a stand-by one.

The injection control unit implements the following recovery strategies in the following conditions:

  • if one of the two potentiometers fails, this allows the throttle to be opened to a maximum of 40° over a long time period;
  • if both potentiometers fail completely, it prevents throttle opening.

Operation

The sensor consists of a case secured to the accelerator pedal support. This contains an axially-located shaft connected to a dual-track potetiometer.A coil spring on the shaft ensures the correct amount of resistance to pressure while a second spring ensures return following release.Operating field from 0° to 70°; mechanical stop at 88°.

Throttle body

Specifications

This is fitted on the intake chamber inlet and regulates the amount of air taken in by the engine.According to the signal received from the accelerator pedal potentiometer, the injection control unit controls the throttle opening by means of a direct current motor built into the throttle body.Throttle opening takes place from 0° to 82°, i.e. including idle speed adjustment range. - The throttle body is equipped with two built-in potentiometers, each of which controls the other.If there is a fault with the two potentiometers or no power supply, depending on the position of the accelerator pedal, the control unit applies a recovery strategy with the consequent inferior operation noticeable to the driver and the EOBD fault diagnosis is disabled.The self-learning procedure does not have be carried out if the injection control unit or the air chamber or the throttle casing is replaced.

Operation _ -the opening of the throttle is managed by an electrically operated motor.

The Marelli 5NF (5SF for Z 16 XEP engines) system operates the motorized throttle according to accelerator pedal requests; a potentiometer is connected to it that sends a voltage signal to the control unit where it is processed and opening laws are produced.The position of the throttle is controlled by the control unit via a potentiometer incorporated in the throttle casing.

INTAKE AIR TEMPERATURE AND PRESSURE SENSOR

Specifications

The pressure and intake air temperature sensor is an integral component which is designed to measure the pressure and the temperature of the air inside the intake manifold. Both pieces of information are used by the injection control unit in defining the quantity of air drawn in by the engine and are then used for calculating the injection time and the ignition point. The sensor is fitted on the intake manifold.
The air temperature sensor consists of an NTC thermistor (Negative Temperature Coefficient). - - The sensor resistance decreases as the temperature increases. The control unit input circuit shares the 5 Volt reference voltage between the sensor resistance and a fixed reference value producing a voltage that is proportional to the resistance and consequently to the temperature.The sensitive element of the pressure sensor is made up of a Wheatstone bridge serigraphed on a ceramic material diaphragm.On one side of the diaphragm is the absolute reference vacuum, whilst on the other side is the pressure from the intake manifold. The (piezoresistive) signal, coming from the distortion suffered by the diaphragm, before being sent to the engine management control unit, is amplified by an electronic circuit contained in the support that houses the ceramic diaphgram. With the engine off, the diaphgram deflects according to atmospheric pressure. Exact reference information on altitude can therefore be obtained with the key on.During operation, the engine generates an intake pressure that produces a mechanical action on the sensor ceramic diphragm which bends to alter the resistance value. Because the power supply from the control unit is maintained strictly constant (5V), the output voltage changes when the resistance value is altered.Electrical propertiesThe electrical specifications of the intake air temperature and pressure sensor are illustrated in the diagram below.
The intake air temperature and pressure sensor is fastened to the air chamber, flywheel side. The location on the Z16XEP engine is illustrated in the diagram below.

IGNITION COILS

Composition

The coils are connected directly to the spark plugs and are the closed magnetic circuit type. They consist of a lamellar pack with a central silicon steel core broken by a fine gap that holds both the windings.The windings are covered by a pressed plastic container and are insulated through immersion in an epoxide resin and quartz compound that gives them excellent dielectric, mechanical and also thermal properties on exposure to high temperatures. The proximity of the primary winding to the magnetic core reduces the magnetic flux losses ensuring the maximum coupling on the secondary winding.Electrical properties:Primary circuit resistance: 0.52-0.62 ohm at 23°CSecondary circuit resistance: 6830-7830 ohm at 23°C.

Vehicle speed sensor

Specifications

The sensor is located on the differential output, by the left driveshaft coupling and transmits the vehicle speed signal to the body computer which, in turn, makes this signal available to the CAN.The control unit takes information relating to the vehicle speed: the signal is also used for the operation of the speedometer.The Hall effect type sensor transmits 16 impulses/rev; it is therefore possible to determine the speed of the vehicle from the frequency of the impulses.
on versions with ABS, the vehicle speed signal is produced by the ABS control unit transmitting information to the body computer which makes it available to the injection control unit via the CAN.

TIMING SENSOR

Specifications

This system uses a phased sequential injection system, in other words the injection of the fuel takes place in sequence for each cylinder during the inlet stage.To achieve this, the electronic control unit also uses a timing signal, in addition to the rpm and TDC signal, to determine the injection point. The signal sent to the control unit is produced by a Hall effect sensor (2) fitted by the inlet side camshaft drive pulley.
1, Retaining bolts2, Hall effect sensor3, Inlet side camshaft pulleyOperating principleA current-carrying semiconductor layer immersed in a normal magnetic field (force lines at right angles to current direction) generates a potential difference known as a Hall voltage at its terminals.If current intensity remains constant, the generated voltage depends on magnetic field intensity alone. Periodic changes in magnetic field intensity are sufficient to generate a modulated electrical signal with frequency proportional to the speed of magnetic field change.This change is achieved by making a magnetic ring (internal part of pulley) with a series of openings pass the sensor. As it moves, the metal part of the ring covers the sensor to block the magnetic field and thus generate a low ouput signal. Conversely, the sensor generates a high signal when the opening is over the sensor and a magnetic field is present.The alternating of the signals depends on the succession of the openings.
1, Power supply (+)2, Signal output3, Earth (-)5, Deflector6, Magnetic material7, GapThe timing sensor is fastened to the flywheel side drive belt guard. The location on the Z16XEP engine is illustrated in the diagram below.