Fuel system FIAT PUNTO 1997 176 / 1.G Owner's Guide

4A*2 Fuel system - single-point petrol Injection models
1 General information and precautions
General information The iAW Weber-Marelli single point Injection (SPI) system is a self-contained engine management system, which controls both the fuel Injection and Ignition (see Illustration), This Chapter deals with the fuel Injection system components only - refer to Chapter 5B for details ol the ignition system components. The fuel Injection system comprises a fuel tank, an electric fuel pump, a fuel filter, fuel supply and return lines, a throttle body with an integral electronic fuel Injector, and an Electronic Control Unit (ECU) together with its associated sensors, actuators and wiring. The fuel pump delivers a constant supply of fuel through a cartridge fitter to the throttle body, and the fuel pressure regulator (integral with the throttle body) maintains a constant fuel pressure at the fuel injector and returns excess fuel to the tank via the return line. This
constant flow system also helps to reduce fuel temperature and prevents vaporisation. Tne fuel injeclor Is opened and closed by an Electronic Control Unit (ECU), which calculates the injection timing and duration according to engine speed, throttle position and rate of opening, Inlet air temperature, coolant temperature and exhaust gas oxygen content information, received from sensors mounted on the engine. inlet air is drawn Into the engine through the air cleaner, which contains a renewable paper filter element. The inlet air temperature is regulated by a vacuum operated valve mounted in the air ducting, which blends air at ambient temperature with hot air, drawn from over the exhaust manifold. Idle speed is controlled by a stepper motor located on the side of the throttle body. Cold starling enrichment is controlled by the ECU using the coolant temperature and inlet air temperature parameters to increase the injector opening duration. The exhaust gas oxygen content is constantly monitored by the ECU via the Lambda (oxygen) sensor, which is mounted in
me exhaust downpipe. The ECU then uses this Information to modify the Injection timing and duration to maintain the optimum air/fuel ratio. An exhaust catalyst Is fitted to all SPI models. The ECU also controls the operation of the activated charcoal filter evaporative loss system • refer to Chapter 4D for further details. It should be noted that fault diagnosis of the I IAW Weber-Marelli system is only possible with dedicated electronic test equipment. Problems with the system should therefore be I referred to a Flat dealer for assessment. Once i the fault has been Identified, the I removal/refitting procedures detailed in the following Sections can then be followed.
Precautions |

A


Warning: Many procedures in thH Chapter require the removal ot fuel lines and connections, which may result in fuel spillage. Before carrying | out any operation on Me fuel system, refer to the precautions given In Safety flrstt at the beginning ot this manual, and follow them Implicitly. Petrol Is a highly dangerous and volatile liquid, and the precautions
1.1 IAW Weber-Marelli single point Injection (SPI) system 1 Fuel
tank
2 Fuel pump 3 Fuel filter 4 Anii'reflux valve 5 Fuel pressure regulator 6 Injector
7 Air cleaner 8 Fuel vapour
trap
9 Idle stepper motor
10
Absolute pressure sensor J11njection/ignition ECU 12 Tnrottle position sensor
13 Engine coolant temperature sensor 14 Intake air temperature sensor 15 Inject'onfignitron dual
relay
16 Ignition coils 17 Rpm and TDC sensor
18 Spark plugs 79 Diagnostic socket 20 EVAP solenoid 21 Lambda/oxygen sensor 22 Rev counter 23 IAW failure warning light

4A*2 Fuel system - single-point petrol Injection models
2.4a Disconnect the large breather hose... ziecessary when handling it cannot be mrstressed. Note that residual pressure
wttf
remain in the tuei lines long after the wh/cte was last used, When disconnecting any fuel line, first depressurise the fuel
system
(see Section 8).
2 Air cleaner and intet system • removal and refitting
1
Accelerator cable -removal, refitting and adjustment l
Removal 1 Remove the air cleaner element as described in Chapter 1A. 2 Disconnect the outer section from the hot
air
tube and the inlet air duct and remove it
from
the engine compartment. 3II necessary remove the inlet air duct. 4 Disconnect Ihe large and small breather
roses
from the inner section of the air cleaner, tftsn unscrew the retaining nuts and lift the section from the throttle body (see lustrations).
5
Recover the sealing ring. Check the ring for condition and renew it if necessary.
6
Wipe clean the inner surfaces of both the merand outer sections of the air cleaner. Refitting 7 Refitting Is a reversal ol removal but renew
tie
element
H
necessary.
3 Inlet air temperature regulator -removal and refitting
Removal t
The
thermostatically-controlled cold air flap cpener is located in the air cleaner outer ttsrig section. To check the unit, disconnect
ire air
inlet duct with the engine cold and use imrrorto check that the flap Is positioned to aJmit only hot air from the shroud on the utaust manifold. Next, warm up the engine
and
check that the flap moves to admit only sett air from the inlet duct. If the unit is faulty fl must be renewed.
2
Remove the air cleaner element as •senbod in Chapter
1
A.
kickdown cable adjustment as described in Chapter 7B before adjusting the accelerator cable • in its rest position the accelerator pedal should have approximately 8.0 mm free travel.
5 Engine management system components -removal and refitting I
2.4b ... and the small breather hose ...
3 Unscrew the retaining screw and remove the regulator from the air cleaner outer section.
Refitting 4 Refitting is a reversal of removal.
Removal 1 Remove the air cleaner and air inlet ducting as desenbed in Section 2. 2 To release the cable from the throttle body, unscrew the outer cable locknuts, then disengage the inner cable from the throttle cam, and release the outer cable from its mounting bracket. 3 Working under the instrument panel inside the vehicle, unhook the cable from the fork at the top of the pedal arm. 4 Release the bulkhead grommet and withdraw the accelerator cable from Inside the engine compartment.
Refitting and adjustment 5 Refitting is a reverse of the removal process, but adjust the cable (by means of the outer cable locknuts) so that there is only a very small amount of free play present at the throttle body end of the inner cable. Have an assistant depress the accelerator pedal, and check that the throttle cam opens fully and returns to the at-rest position, then secureJy tighten the cable locknuts. On Selecta models, check the
Note: Refer to the warning given in Section 1 before proceeding. Throttle body assembly
Removal 1 Remove the air cleaner and air duct as desenbed in Section 2. 2 Disconnect the wiring connectors from the throttle potentiometer, idle control stepper motor, inlet air temperature sensor and the injector wiring loom connector situated on the front of the throttle body. 3 Depressurise the fuel system with reference to Section 8, then release the retaining clips and disconnect the fuel feed and return hoses from the throttle body assembly, if the original Fiat retaining clips are still fitted, cut the clips and discard them; replace them with standard luel hose clips on refitting. 4 Slacken the accelerator cable locknuts, then disengage the inner cable from the throttle cam and froe tho outer cable from its retaining bracket. Position the cable clear of the throttle body. 5 Disconnect the EVAP purge valve hose, and the MAP sensor hose from the rear of the throttle body. 6 Slacken and remove the four bolts securing the throttle body assembly to tho Inlet manifold, then remove the assembly along with its insulating spacer. Refitting 7 Refitting is a reversal of the removal pro-cedure, bearing in mind the following points: a) Examine the insulating spacer for signs of damage, and renew //necessary, b) Ensure that the throttle body, inlet manifold and insulating spacer ma ting surfaces are clean and dry, then fit the throttle body and spacer, and securely tighten the retaining bolts.
2.4c ... then remove the retaining nuts. 2.4d ... and remove the air cleaner inner section

4A*2 Fuel system - single-point petrol Injection models
motor c) Ensure that all hoses are correctly reconnected and, where necessary, that their retaining clips are securely tightened. d) Adjust the accelerator cable as described In Section 4.
Fuel injector Note: If a faulty Injector Is suspected, before condemning the Injector, it is worth vying the effect of one of the proprietary Injector cleaning treatments. Removal 8 Remove the air cleaner and air duct as described In Section 2. 9 Disconnect the wiring then unscrew the mounting screws and remove Ihe Injector from the throttle body. Refitting 10 Refitting is a reversal of removal.
Fuel pressure regulator
Removal 11 Remove Ihe air cleaner and air duel as described In Section 2. 12 Using a marker pen. make alignment marks between the regulator cover end the throttle body, then undo the four retaining
screws. As the screws are loosened, place a rag over the cover to catch any fuel spray which may be released. 13 Lift off the cover, then remove the spring and withdraw the diaphragm, noting Its correct fitted orientation. Remove all traces of dirt, and examine the diaphragm for signs of splitting. If damage Is found, it will be necessary to renew the complete upper throttle body assembly. Refitting 14 Refitting is a reversal of removal ensuring that the diaphragm and cover are fitted the correct way round, and that the retaining screws are securely tightened,
Idle control stepper motor
Removal 15 Disconnect the battery negative terminal (refer to Disconnecting the battery In the Reference Section of this manual), then remove the air cleaner and air duct as described in Section 2. 16 Using a crosshead screwdriver, unscrew the mounting screws and remove the stepper motor from the throttle body. Recover the gaskei (see illustration). 17 Clean the unit and check for damage and wear. Refitting 18 When refitting the unit use a new gasket and make sure that the plunger is inserted correctly using the following procedure. Insert the unit and refit the mounting screws loosely. Reconnect the wiring then switch on the ignition several times so that the unit centralises itself. Finally fully tighten the mounting screws to the specified torque. Note: The mounting screws are covered with a locking agent and must be renewed every time they are removed 19 Leave the battery negative terminal disconnected for about 20 minutes - the injection/ignition ECU will position the Idle control stepper motor correctly the first time the engine is started. Reconnect the battery negative terminal.
Throttle potentiometer
Removal 20 Remove the air cleaner and air duct as described in Section 2. 21 Disconnect the wiring from the throttle potentiometer. 22 Using an Allen key unscrew the mounting screws then withdraw the unit from the throttle body (see Illustration). Note: The mounting screws ere covered with a locking agent and must be renewed every time they are removed. Refitting 23 When refitting the unit make sure that the pin Is correctly engaged, and tighten the mounting screws to the specified torque. 24 If a Rat test Instrument is available, the
operation of the throttle potentiometer can be checked at this stage. Before connecting the wiring first turn Ihe ignition key to position MAR and wait a few seconds, then return the key to the STOP position, Reconnect the wiring and connect the test instrument. Turn the Ignition key to the MAR position and cancel the error that will appear. The throttle position Indicated should be between 0° and 4°. If greater than this, check thai the accelerator cable is correctly adjusted however If the correct reading cannot be obtained renew the unit.
Inlet air temperature sensor
Removal 25 Remove the throtlle body assembly as described earlier In this Section. 28 Extract the plastic pins and remove the press-fit cover from the top of the throttle body. 27 Invert the cover then unscrew the mounting screws and remove the Inlet air temperature sensor from the cover. Refitting 28 Refining Is a reversal of removal.
Manifold absolute pressure (MAP) sensor
Removal 29 The manifold absolute pressure sensor is located on the left-hand side of the bulkhead. 30 Unscrew the mounting screws and remove the sensor from the bulkhead, Disconnect the wiring and vacuum pipe. Refitting 31 Refitting is a reversal of removal, but check the condition of the vacuum pipe and renew it if necessary.
Coolant temperature sensor
Removal 32 The coolant temperature sensor Is located on the left-hand side of the inlet manifold. Drain the cooling system as described In Chapter 1A before removing it. 33 Disconnect the wiring. 34 Unscrew the sensor and remove It from the Inlet manifold. If using a socket take care not to damage Ihe wiring connector on the sensor. Refitting 35 Refitting Is a reversal of removal bui tighten Ihe sensor to the specified torque. Do not exceed the specified torque otherwise the unit may be damaged.
Crankshaft TDC sensor
Removal 36 The crankshaft TDC sensor Is located on the front side of the crankshaft pulley. Firmly apply the handbrake, then jack up the front of the car Bnd support It securely on axle stands (see Jacking end vehicle support). Remove 5.22 Throttle potentiometer mounting screws

Ihe right-hand front roadwheel and the protective plastic cover under the wheelarch. 37 Disconnect the sensor wiring plug on the front of the engine. 38 Detach the sensor from its mounting. Refitting 39 After refitting Ihe sensor use a feeler blade to check that the gap between sensor and the serrated part of the crankshaft pulley Is between 0.5 and 1.S mm. No adjustment is possible and if the gap is incorrect the sensor and pulley should be checked for possible damage.
Electronic control unit (ECU)
Removal Note: 77ie engine management system has a (earning capability which allows the ECU to store details of the engine's running
characteristics
in its memory,
This
memory
will
tie erased by the disconnection of the battery
cables,
with the resuit that the engine may idle
roughly,
or lack performance for a while, until
the
engine's characteristics are re-teamt. 40 The ECU {electronic control unit) is located on the right-hand Inner wing (see illustration). The 3-pin socket by the ECU is for connection of diagnostic test equipment. 41 Disconnect the battery negative terminal (refer to D/sconnecffng the battery in the Reference Section of this manual). 42 Disconnect the ECU wiring connector, then undo the retaining nuts and remove the unit from the bracket In the engine compartment. Refitting 43 Refitting Is a reversal of removal making sure that the wiring connector is securely reconnected. Inertia safety switch
Removal 44 The inertia safety switch is located by the left-hand side passenger seat. First pull back
the
carpet for access. 45 Disconnect the wiring then unbolt the switch. Refitting 48 Refitting is a reversal of removal.
Fuel injection system relays
Removal 47 The fuel injection system relay is located under a plastic cover on the bulkhead. The MAP sensor is also located under the same cover. 48 Two separate relays are incorporated in the single housing; the left-hand relay has a 5 amp fuse and the right-hand relay has a 25 amp fuse. The main purpose of the relays is to supply current to the fuel pump, ignition coils, oxygen sensor. Injectors and EVAP solenoid. The main relay is controlled by the ignition switch.
4A*2 Fuel system - single-point petrol Injection models
6 Fuel pump/fuel gauge sender unit -removal and refitting
Removal Note: Refer to the warning given in Section 1 before proceeding. 1 Disconnect the battery negative terminal (refer to Disconnecting the battery in the Reference Section of this manual). 2 Remove the rear seat as described in Chapter 11. Prise the fuel pump access cover out of the floor panel to gain access to the pump unit. 3 Disconnect the wiring connector. 4 Bearing in mind the warning given in Section t, disconnect the fuel supply and return lines from the pump unit by pressing the tabs (see illustration). Plug the ends of the lines or cover them with adhesive tape. 5 Using a suitable toot, unscrew the large ring nut and carefully withdraw the fuel pump/fuel tank sender unit assembly from the fuel tank, along with its sealing ring. 6 If necessary, the unit can be dismantled and the pump and sender unit separated. If this is the case, carefully note the correct
fitted positions of oil components while dismantling the unit, and use these notes on reassembly to ensure that all items are correctly fitted.
Refitting 7 Refitting is a reversal of the removal procedure using a new sealing ring. Prior to refitting the access cover, reconnect the battery, then start the engine and check the feed and return unions for signs of leakage.
5.40 ECU located on the right-hand inner wing 49 Remove the cover and pull the relay directly from its socket. Refitting 50 Refitting Is a reversal of removal.
7 Fuel tank -removal and refitting
6.4 Press the tabs Indicated to disconnect the fuel supply and return tines
Note: Refer to the warning given in Section 1 before proceeding.
Removal 1 Before removing the fuel tank, all fuel must be drained from the tank. Since a fuel tank drain plug is not provided, it is therefore preferable to carry out the removal operation when the tank is nearly empty. Before proceeding, disconnect the battery negative terminal (refer to Disconnecting the battery In the Reference Section of this manual), and syphon or hand-pump the remaining fuel from the tank. 2 Remove the fuel pump/fuel gauge sender unit as described in Section 6. 3 Chock the front wheels, then jack up the rear of the vehicle and support on axle stands (see Jacking and vehicle support). 4 Loosen the clip and disconnect the filler pipe from the nght-hand side of the fuel tank. 5 Undo the tank flange and strap mounting bolts, then lower the tank out of position until It is possible to access the hose connections on top of the tank. 6 Loosen the clips and disconnect the EVAP purge hose and breather hose from the fuel tank. If necessary, the filler neck can be detached from the body. 7 Check that all hoses and wiring is disconnected, then remove the tank from underneath the vehicle. Refitting 8 Refitting is a reversal of the removal procedure, ensuring all hoses are correctly routed and securely reconnected.
8 Fuel injection system - ^ depressurisation
Note: Refer to the warning given In Section t before proceeding.

A


Warning; The following procedure will merely relievo the pressure in the fuel system • remember that fuel will still be present In the system components and take precautions accor-dingly before disconnecting any of them.

4A*2 Fuel system - single-point petrol Injection models
1 The luel system referred to In this Section is defined as the tank-mounted fuel pump, the fuel litter, the throttle body and pressure regulator components, and the metal pipes and flexible hoses of the fuel lines between these components. All ihese contain fuel which will be under pressure while the engine Is running and/or while tha Ignition is switched on. The pressure will remain for some time after tho ignition has been switched off, and must be relieved before any of these components are disturbed (or servicing work. 2 Disconnect the battery negative terminal (refer to D/sconnecf/ngr the battery in the Reference Section of this manual), 3 Place a container beneath the relevant connection/union to be disconnected, and have a large rag ready to soak up any escaping fuel not being caught by the container. 4 Slowly loosen the connection or union nut (as applicable) to avoid a sudden release of pressure, and wrap tho rag around the connection to catch any fuel spray which may be expelled. Once the pressure is released, disconnect the fuel line, and Insert plugs to minimise fuel loss and prevent the entry of dirt Into the fuel system.
9 Inlet manifold -removal and refitting ^
Note: Refer to the warning given In Section 1 before proceeding.
Removal 1 Remove the throttle body assembly as described in Section 5. 2 Drain the cooling system as described in Chapter 1A. 3 Disconnect the winng connector from the coolanl temperature sensor (situated on the left-hand sidB of the manifold). 4 Undo the bolt securing the accelerator cable mounting bracket to the manifold, and position it clear of the manifold. 5 Slacken the retaining clip and disconnect tha coolant hose from the rear of the manifold. 6 Disconnect the brake vacuum hose. 7 Undo the seven manifold retaining nuts and
10.2 The diagnostic connector la located behind the ECU bolts, and remove (he manifold from the engine. Remove the gasket and discard It; a new one should be used on refitting.
Refitting 8 Refitting is a reverse of the removal procedure, noting the following points: a) Ensure that the manifold and cylinder head mating surfaces are clean and dry, and fit a nev/ manifold gasket. Refit the manifold and securely tighten Its retaining nuts. b) Ensure that all relevant hoses are reconnected fo their original positions and are securely held (where necessary) by the retaining clips. c) Refit the throttle body assembly with reference to Section S. d) On completion, refill the cooling system as described In Chapter 1A.
correctly adjusted, and that the engine breather hoses are clear and undamaged. 2 If these checks fall to reveal the cause of the problem, the vehicle should be taken to a suitably-equipped Fiat dealer for testing. A wiring block connector Is Incorporated In the engine management circuit, into which a special electronic diagnostic tester can be plugged; the connector is situated behind the ECU (see Illustration). The tester will locate the fault quickly and simply, alleviating the need to test all the system components Individually, which is a time-consuming operation that carries a high risk of damaging the ECU.
Adjustments 3 As mentioned above, the idle speed and mixture adjustment are all monitored and controlled by the ECU, and are not adjustable Experienced home mechanics with a considerable amount of skill and equipment (including a good-quality tachometer and a good-quality, carefully calibrated exhaust gas analyser) may be able to check the exhaust CO level and ihe idle speed. However, If thes* are found lo be in need of adjustment, the car must be taken to a suitably-equipped Flat dealer for testing using the special test equipment which is plugged into the diagnostic connector.
11 Unleaded petrol -general Information and usage
10 Fuel injection system - & testing and adjustment S
Testing 1 If a fault appears in the fuel injection system, first ensure that all the system winng connectors are securely connected and free of corrosion. Then ensure that the fault Is not due to poor maintenance; ie, check that the air cleanor fitter element is clean, the spark plugs are In good condition and correctly gapped, that tho valve clearances are
Note: The information given in this Chapter
is
correct at the time of writing. If updated Information is thought to be required, check with a Fiat dealer. If travelling abroad, consult one of the motonng organisations (or a similar authority) for advice on the fuel available. 1 All petrol models are fitted with a catalytic converter and must be run on unleaded fuel only - the fuel recommended by Flat is given In the Specifications of this Chapter. Under no circumstances should leaded fuei (UK 4-slar) be used, as this may damage the converter. 2 Super unleaded petrol (98 octane) can also be used in all models if wished, though there is no advantage in doing so.

4B*1
Chapter 4 Part B:
Fuel system - multi-point petrol injection models
Contents
Accelerator cable - removal, refitting and adjustment 4 Air cleaner and Inlet system • removal and refitting 2 Air cleaner filter element renewal See Chapter 1A Engine management system components (1242 cc, 8-valve engines) -removal and refitting 5 Engine management system components (1242 cc, 16-valve engines) - removal and refitting 6 Fuel filter renewal See Chapter 1A Fuel Injection system - depressurisation 9
Degrees of difficulty
Fuel injection system - testing and adjustment 11 Fuel pump and fuel gauge sender unit - removal and refitting 7 Fuel tank - removal and refitting 8 General Information and precautions 1 Idle speed and mixture adjustment See Chapter 1A Inlet air temperature regulator - removal and refitting 3 Inlet manifold - removal and refitting 10 Unleaded petrol • general Information and usage 12

Easy, suitable
for ^
novice with
Ittie experience ^
Fairly
easy,
suitable Jk for beginner
with
® someexperiencs ^
FaMycSffiait, J^ suitable
for
competent ^
DIY mechanic
^
Difficult
suitable
for experienced BY SJ mechanic ^

Very difficult,
^
suitable
for expert
DIY
jR or professional ^
Specifications
System type
Fuel system data Fuel pump type Fuel pump delivery rate: 1242 cc (8-vatve) engine 1242 cc (16-valve) engine Regulated fuel pressure: 1242 cc (8-vaive) engine: Pre-1998 models 1998 models onward 1242 cc (16*valve) engine Crankshaft TDC sensor resistance al 20°C Injector electrical resistance: Pre-1998 models 1998 models onward Injector duration (at Idle)
Recommended fuel Minimum octane rating
Torque wrench settings Coolant temperature sensor
Idle
control stepper motor Inlet manifold brake servo union Inlet manifold upper section-to-lower section (16-valve engines) Inlet manifold-to-cylinder head (16-valve engines) Inlet manlfold-to-cylinder head (8-valve engines) Throttle body to manifold Throttle potentiometer
Weber-Marelli integrated multi-point fuel injection/ignition system
Electric, immersed In fuel tank
120 Hires/hour minimum 110 litres/hour minimum
2.5 bars 3.5 bars 3.0 bars 650 to 720 ohms
16.2 ohms 13.8 to 15.2 ohms 2.0 ms
95 RON unleaded
Nm Ibfft a 2 4 3 35 26 9 7 15 11 27 20 7 5 3 2

4A*2 Fuel system -
single-point
petrol Injection models
1 General information and precautions
General information The
LAW
Weber-Maretil multi-point Injection (MPI) system is a self-contained engine management system, which controls both the fuel injoction and Ignition (see Illustrations). This Chapter deals with the fuel Injection system components only - refer to Chapter 5B for details of the ignition system components. The fuel injection system comprises a fuel tank, an electric fuel pump, a fuel filter, fuel supply end return lines, a throttle body, a fuel rail with four electronic Injectors, and an Electronic Control Unit (ECU) together with its associated sensors, actuators and wiring. On pre-1998, 8-valve engines and all 16-valve engines, the fuel pump delivers a constant supply of fuel through a cartridge filter to the fuel rail, and the fuel pressure regulator (located on Ihe fuel rail) maintains a constant fuel pressure at the fuel Injectors and returns excess fuel to the tank via the return
line, This constant flow system also helps to reduce fuel temperature and prevents vaporisation. On later 8-valve engines, a returnless fuel system is used. With this arrangement, the fuel filter and fuel pressure regulator are an integral part of the fuel pump assembly located In the fuel tank. The regulator maintains a constant fuel pressure in the supply line lo the fuel rail and allows excess fuel to recirculate in the fuel tank, by means of a bypass channel, if the regulated fuel pressure is exceeded. As the fuel filler Is an integral part of the pump assembly, fuel filter renewal Is no longer necessary as part of the maintenance and servicing schedule. The fuel injectors are opened and closed by an Electronic Control Unit (ECU), which calculates the Injection timing and duration according to engine speed, throttle position and rate of opening, inlet air temperature, coolant temperature and exhaust gas oxygen content information, received from sensors mounted on the engine. The injectors are operated simultaneously (le not sequentially) and Inject half of the quantity of fuel required on each turn of the crankshaft. Inlet air Is drawn into the engine through
the air cleaner, which contains a renewable paper filter element. On 8-valve engines, the Inlet air temperature is regulated by a vacuum operated valve mounted in the air ducting, which blends air at ambient temperature with hot air, drawn Irom over the exhaust | manifold. Idle speed Is controlled by a stepper motor 1 located on the side of the throttle body. Cold storting enrichment is controlled by the ECU using the coolant temperature and Inlet air temperature parameters to Increase the Injector opening duration. The exhaust gas oxygen content it constantly monitored by the ECU via the Lambda/oxygen sensor, whioh Is mounted in the exhaust downpipe. The ECU then uses this Information to modify the Injection timing and duration to maintain the optimum air/fuel ratio. An exhaust catalyst is fitted to all models. The ECU also controls the operation of the activated charcoal filler evaporative loss system - refer to Chapter 4D for further details. It should be noted that fault diagnosis of the IAW Weber-Marelll system Is only possible with dedicated electronic test equipment.
1.1a IAW Weber-Marelii multt-point Injection (MPi) system (8-valve engines) f Fuel
tank
7 Air
cleaner
13 Coolant temperature sensor 19 Diagnostic socket 2 Fuel pump 8 Fuel vapour trvp 14 Intake air temperature 20
EVAP
solenoid 3 Filter (pre-1998 models) 9 Idle control stepper motor sensor 21 Lambda/oxygen sensor 4 Fuel
rail
10 Manifold absolute pressure 15 Duel
relay
22 Rev counter 5 Pressure regulator
(pre-1998
sensor 16 Ignition colls 23 IAW failure warning light models)
11 ECU
17 Rpm and TDC sensor 24 Anti-refhjx
valve
6 Injectors 12 Throttle position sensor 18 Spark piugs

4A*2 Fuel system -
single-point
petrol Injection models
1.1b IAW Weber-Marelli multi-point injection (MPI) system (16-valve engines) J Fuel
tank
2 Fuel pump 3 Multi-purpose
valve
4 Safety
valve
5 Anti-reflux
valve
6 F/fter 7 Battery 8
EVAP
solenoid
9 Dual
relay
10 Ignition switch 111nertia switch
12
Air conditioning compressor
13
Fuse 14 Throttle position sensor

1$
idle control stepper motor 17 Ignition coils 18 Sparkplugs 19 Fuel
rail
20 Pressure regulator 21 Injectors
15
Intake air temperature/pressure 22 Coolant temperature sensor sensor 23 Lambda/oxygen sensor
24 Rpm and TDC sensor 25 Engine immobiliser control unit 26 Catalytic converter 27 IAW failure warning light 28 EVAP canister 29 ECU 30 Diagnostic socket 31 Rev counter
Problems with the system should therefore be referred to a Fiat dealer for assessment. Once the fault has been Identified, the removal/ refitting procedures detailed in the following Sections can then be followed.
Precautions

A


Warning: Many procedures In this Chapter require the removal of fuel lines and connections, which may result In fuel spillage. Before carrying out any operation on the fuel system, refer to the precautions given In Safety flrstl 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. Note that residual pressure will remain in the fuel lines long after the vehicle was last used, When disconnecting tny fuel line, first depressurise the fuel system {see Section 9).
2 Air cleaner and inlet system Sk - removal
and
refitting ^
Removal
1242 cc (8-valve) engines 1 Remove the air cleaner element as described In Chapter 1A. 2 Disconnect the outer section from the hot air tube and the Inlet air duct and remove it from the engine compartment. 3 If necessary remove the inlet air duct. 4 Disconnect the large and small breather hoses from the inner section of the air cleaner, then unscrew the retaining nuts and lift the section from the throttle body. 5 Recover the sealing ring. Check the nng for condition and renew it it necessary. 6 Wipe clean the inner surfaces of both the Inner and outer sections of the air cleaner,
1242 cc (16-valve) engines 7 Release the hose clip and disconnect the inlet air duct from the resonator (see illustration).
2.7 Release the hose clip and disconnect the inlet air duct from the resonator

4A*2 Fuel system -
single-point
petrol Injection models
2.8 Undo tho two bolts securing the resonator to the camshaft cover
8 Undo the two bolts securing the resonator to the camshaft cover (see illustration) 9 Release ihe wiring loom support clip from the slot on the side of the resonator lower extension, then lift the resonator off the camshaft cover (see illustrations). Disconnect Ihe crankcase breather hose from the underside of tho resonator and remove the resonator from the engine. 10 Undo the nuts secunng the sides of the air cleaner to the mounting brackets at the front of the engino. 11 Release the hose clip and disconnect the inlet air duct from the throttle body. 12 Release the crankcase ventifation hose from the pipe stub on the camshaft cover then remove the air cleaner and inlet air duct assembly from the engine (see illustration).
Refitting 13 Refitting is a reversal of removal but renew the air cleaner element as described In Chapter
1 A,
if necessary.
Inlet air temperature regulator -liWfii' I
2.9o Release the wiring support clip (arrowed) from the slot on the resonator lower extension ...
the shroud on the exhaust manifold. Next, warm up tho engine and check that the flap moves to admit only cold air from the Inlet duct. If the unit is faulty it must be renewed. 2 Remove the air cleaner element as described in Chapter
1
A. 3 Unscrew tha retaining screw and remove tho regulator from the air cleaner outer section.
Refitting 4 Rofitting is a reversal of removal.
I
Removal 1 The thermostatically-controlled cold air flop opener, fitted to 8-valve engines, is located in the air cleaner outer cos>ng section. To check lha unit, disconnect the atr inlet duct with the engine cold and use a mirror to check that the flap Is positioned to admit only not air from
2.12 Removing the air cleaner and Inlet air duct assembly
4 Accelerator cable -removal, refitting and adjustment
1242 cc (8-valve) engines
Removal 1 Remove Ihe air cleaner as described In Section 2. 2 To release the cable from the throttle body, unscrew the outer cable locknuls, then disengage the inner cable from the throttle cam, and release the outer cable from its mounting bracket, 3 Wording under the instrument panel inside the vehicle, unhook the cable from tho fork at the top of the pedal arm. 4 Release the bulkhead grommel and withdraw tho accelerator cable from inside Ihe engine compartment. Refitting and adjustment 5 Refitting is a reverse of the removal process, but ad|ust the cable (by means of the outer cable locknuts} so that there Is only a very small amount of free play present at the throttle body end of the inner cablo. Have an assistant depress the accelerator pedal and check that the throttlo cam opens fully and returns to the at-rest position, then securely tighten the cable locknuts.
1242 cc (16-valve) engines
Removal 6 Dlsconnoel the battery negative terminal (refer to Disconnecting the battery in the Reference Section of this manual), 7 Remove the resonator, air cleaner and Inlet air duct as described in Section 2.
camshaft cover
8 Undo the engine management ECU mounting bracket bolts, release the ECU wiring loom from Ihe support clips and move tho ECU and wiring loom to one side for access to the accelerator cable. 9 Free the accelerator inner cable from the throttle cam, remove the outer cable spring clip, then pull the outer cable out from its mounting bracket rubber grommet (see illustration). 10 Trace the cable back to its entry point in the engine compartment bulkhead and undo the bulkhead support bracket mounting bolt. 11 Working back along the length of the cable, free It from any retaining clips or ties, noting its correct routing. 12 Working under the instrument panel Inside the vehicle, unhook the cable from the fork at the top of the pedal arm. 13 Release the bulkhead support bracket and withdraw the accelerator cable from inside the engino compartment. Refitting end adjustment
14 Refitting is a reverse of the removal process, but adjust the cable as follows before refitting the outer cable spring clip. 16 Ensuring that the throttle cam is fully against its stop, gently pull the cable out of its grommet until all free play Is removed from the inner cable. 16 With the cable held in this position, lit the spring clip to tho first outer cable groove visible in front of the mounting brackot rubber grommet. This should leave a small amount of freeplay in tho inner cable which is necessary to ensure correct throttle operation.
4.9 Accelerator outer cable spring clip (arrowed)

4A*2 Fuel system -
single-point
petrol Injection models
17 Have an assistant depress the accelerator pedal and check that the throttle cam opens luily and returns smoothly to its stop. If necessary, reposition the spring clip In the next outer cable groove and recheck the throttle operation. 18 Refit the remainder of the disturbed components.
5 Engine management
system
^ components
(1242
cc, 8-vatve § engines) -
removal and refitting
^
Note: Refer to the warning given In Section T
before
proceeding.
Throttle body assembly
Removal 1 Remove the air cleaner and inlet air duct as described in Section 2. 2 Disconnect the wiring connectors from the throttle potentiometer, the idle control stepper motor and the inlet air temperature sensor. 3 Slacken the accelerator cable locknuts, then disengage the inner cable from the throttle cam and free the outer cable from its retaining bracket. Position the cable clear of the throttle body. 4 Unclip and disconnect the EVAP purge valve hose, and Ihe MAP sensor hose from the rear of the throttle body then, where applicable, disconnect the fuel pressure regulator vacuum hose from the front of the throttle body. 5 Slacken and remove the four bolts securing the throttle body assembly to the inlet manifold, then remove the assembly along with its insulating spacer. Refitting 6 Refitting is a reversal of the removal pro-cedure. bearing in mind the following points: 4! Examine the Insulating spacer for signs of damage, and renew If necessary. b) Ensure the throttle body, inlet manifold and insulating spacer mating surfaces are clean and dry, then fit the throttle body and spacer, and securely tighten the retaining bolts. c) Ensure ail hoses are correctly reconnected and, where necessary, /her their retaining clips are securely tightened. d) Adjust the accelerator cable as described in Section 4.

Fuel
rail and injectors
Removal 7 Disconnect the battery negative terminal (refer to Disconnecting tho battery in the Reference Section of this manual). 6 Remove the throttle body assembly as described earlier in this Section, however it is only necessary to move the unit to one side for access to the fuel rail and therefore it Is unnecessary to disconnect the accelerator caWe and hoses etc.
9 Depressurise Ihe fuel system as described in Section 9. 10 Loosen the clips or release the quick-release couplings and disconnect the fuel inlet and, on pre-1998 models, outlet hoses from the fuel rail. Note the fitted positions of the hoses to aid refitting later. 11 Unplug the ln}ector wiring harness connectors, labelling them to aid correct refitting later. 12 Unscrew the bolts securing the fuel rail assembly to the Inlet manifold, then carefully pull the Injectors from the Inlet manifold. Remove the assembly from the engine and remove the injector lower O-ring seals. 13 The injectors can be removed Individually from the fuel rail by extracting the relevant metal clip and easing Ihe injector out of the rail. Remove the injector upper O-ring seals (see illustration).
14 On pre-1998 models, if necessary remove the retaining clip and remove the fuel pressure regulator from the fuel rail. 15 Check the electrical resistance of the injector using a multimeter and compare It with the Specifications. Note: If a faulty Injector is suspected, before condemning the injector, It is worth trying the effect of one of the proprietary injector-cleaning treatments. Refitting 16 Refit the injectors and fuel rail by following the removal procedure, in reverse, noting the following points: a) Renew the injector O-rlng seals, and smear them with a little Vaseline before assembling. Take care when fitting the injectors to the fuel rail and do not press them in further than required to fit the retaining clip otherwise the O-ring seal may be damaged.
1 Fuel rail 2 Fuel pressure regulator 3 Injectors
5.13 Fuel rail and Injector removal 4 Vacuum stub connect/on 5 Fuel inlet hose 6 Fuel return hose
7 Mounting bolts 8 Injector mounting dip 9 Injector mounting dip