1997 FIAT PUNTO Ignition fault

5B*2 Ignition system - petrol models
1 HT leads 2 Support 3 Cover mounting bdt 4 Ignition coifs
5 Washer 6 Washer 7 Coil mounting bolt
1.2s Ignition coils and HT leads 9 Washer 10 Coil mounting bracket
11
Nut
12 Waslrer 13 Spark plugs 14 Coll cover 15 HT lead support
16 HT lead support 17HTlead support 18 Seat Id Bracket
1 General information
The ignition system is integrated with the fuel injection system to form a combined engine management system under the control of one ECU (see the relevant part of Chapter 4 lor further Information). The Ignition side of the system is of the static (distributorless) type, consisting only of two twin-output Ignition coils located on the left-hand side of the cylinder head. Each ignition coil supplies two cylinders (one coll supplies cylinders 1 and 4, and the other cylinders 2 and 3) (see Illustrations). Under the control of the ECU, the ignition coils operate on the wasted spark principle, ie. each spark plug sparks twice for every cycle of the engine, once on the compression stroke and once on tho exhaust stroke. The spark voltage is greatest in the cylinder which Is under compression, the other cylinder
having a very weak spark which has no effect on the exhaust gases. The ECU uses Its Inputs from the various sensors to calculate the required ignition advance setting and coil chorging time.
1.2b Ignition coll circuit 1 Primary windings 2 Secondary windings 3 Power module
ECU) 4 Spark plugs
2 Ignition system -testing i

A


Warning: Voltages produced
by
an electronic Ignition system an considerably higher than (hose produced by conventional Ignition systems. Extreme care must be tak»n when working on tho system with thi Ignition switched on. Persons wilfl surgically-implanted cardiac pacemaker devices should keep well clear ot the ignition circuits, components and (oaf equipment 1 If a fault appears In the engine management (fuel injection/ignition) system first ensure that the fault is not due to a poor electrical connection or poor maintenance: ie, checK lhat the air cleaner filter element is clean, tht spark plugs are In good condition and correctly gapped, lhat the engine breather hoses are clear and undamaged, referring to

Ignition system - petrol models 5B®3
Chapter 1A tor further information. Also check tnat tha accelerator cable is correctly adjusted
as
described in the relevant part of Chapter 4. If the engine is running very roughly, check the compression pressures and the valve clearances as descnbed In the relevant parts of Chapters 1 and 2. 2
H
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 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. 3 The only Ignition system checks which can
oe
earned out by the home mechanic are those cescribed in Chapter 1A, relating to the spark plugs, and the ignition coll test descnbed In this Chapter. If necessary, the system wiring and wiring connectors can oe checked as descnbed in Chapter 12, Section 2, ensuring that the ECU wiring connector(s) have first
been
disconnected.
3 Ignition HT coil - ^ removal, testing and refitting
Removal 1 On 6-valve engines, unscrew the boll and remove the plastic cover from the left-hand
end
of the cylinder head (see Illustration). On 15-valve engines, remove the air cleaner, resonator and Inlet air duct as described in Chapter 4B. 2 Identify the two HT leads for position then disconnect them from the coil HT terminals jsee illustration). 3 Disconnect the LT wiring plug.
4 Unscrew the mounting bolts and remove the relevant ignition coil from the end of the cylinder head,
Testing 5 Testing of the coil consists of using a multimeter set to its resistance function, to check the primary and secondary windings for continuity and resistance. Compare the results obtained to those given In the Specifications at the start of this Chapter. Note the resistance of the coil windings varies slightly according to the coil temperature; the results In the Specifications are approximate values for the coil at 20°C. 6 Check that there is no continuity between the HT lead terminals and the coil body/ mourning bracket. 7 Note that with the ignition switched on and the engine stationary, voltage will only be supplied to the ignition cotls for approx-imately 2 seconds. However, when tho engine is being cranked or running, voltage will be continually supplied. 8 If faulty, the coil should be renewed.
Refitting 9 Refitting ts a reversal of the removal procedure ensuring that the winng and HT leads are correctly reconnected (see illustration).
4 ignition timing • checking and adjustment
1 The Ignition timing is constantly being monitored and adjusted by the engine management ECU, and although it is possible to check the base ignition liming using a standard timing light It is not possible to adjust it. 2 For those wishing to check the ignition timing a stroboscope timing light will be required, and it will need to be the type which
3.1 Removing the ignition coll cover
can determine the amount of advance from the TDC markings on the crankshaft pulley or flywheel. It Is recommended that the timing mark is highlighted as follows. 3 Remove the plug from the top of the transmission then turn tho engine slowly (raise the front right-hand wheel and engage 4th gear) until the timing mark scribed on the edge of the flywheel appears in the aperture. Highlight the line with quick-drying white paint - typist's correction fluid is ideal. 4 Start the engine and run It to normal operating temperature, then stop it. 5 Connect the timing light to No 1 cylinder spark plug lead (No 1 cylinder Is at the timing belt end of the engine) as described in the timing light manufacturer's Instructions. 6 Start the engine, allowing it to idle at the specified speed (Chapter 1A), and point the timing light at the transmission housing aperture. Adjust the timing light until the TDC marks are aligned with each other and read off the amount of advance. 7 If the ignition timing is incorrect, the car should be taken to a Fiat dealer who will be able to check the system quickly using special diagnostic equipment. 8 After making the check stop the engine, disconnect the timing light and refit the plug to the transmission.
3.2 HT terminals (1) and LT wiring plugs (2) on the two ignition colls 3.9 Ignition colt connections

501
Chapter 5 PartC:
Preheating system - diesel models
Contents
Glow plugs - removal, inspection and refitting 2 Preheating system - description and testing 1 Preheating system control unit - removal and refitting 3
Degrees of difficulty

Ea3y, suitable
for &
novice with little
|| experience ^

Fairty easy,
suitable for beginner with
some experience
jQ
Fairty diffctit, ^
suitable
for competent
DIY
mechanic

Difficult, suitable for
experienced DIY JR mechanic ^
Very difficult, ^ suitable fbrexpertDfY JR or professional ^
Specifications
Torque wrench setting Nm ibf ft Heater glow plugs 15 11
1 Preheating system -description and testing
Description 1 Each swirl chamber has a heater plug (commonly called a glow plug) screwed into it. The plugs are electrically-operated before and during start-up when the engine is cold. 2 Electrical feed to the glow plugs Is controlled by a relay/timer unit. The coolant temperature determines the period of heating that takes place. 3 A warning light in the instnjment panel tells the driver that preheating is taking place. When the light goes out, the engine is ready to be started. The voltags supply to the glow plugs continues for several seconds after the light goes out, If no attempt is made to start, the timer then cuts off the supply, In order to avoid draining the battery and overheating the glow plugs.
Testing 4 If the system malfunctions, testing is ultimately by substitution of known good units, but some preliminary checks may be made as follows. 5 Connect a voltmeter or 12-volt test lamp between the glow plug supply cable and earth (engine or vehicle metal). Make sure that the live connection is kept clear of the engine and bodywork. 6 Have an assistant switch on the ignition, and check that vottage is applied to the glow plugs. Note the time for which the warning light Is lit. and the total time for which voltage Is applied before the system cuts out. Switch off the ignition. 7 At an under-bonnet temperature of 20°C. typical times noted should be 5 or 6 seconds for warning light operation, followed by a further 10 seconds supply after the light goes out. Warning light time will increase with lower temperatures and decrease with higher temp-eratures.
8 If there Is no supply at all, the relay or associated winng is at fault. 9 To locate a defective glow plug, disconnect the main supply cable and the interconnecting strap from the top of the glow plugs. Be careful not to drop the nuts and washers. 10 Use a continuity tester, or a 12-voH test lamp connected to the battery positive terminal, to check for continuity between each glow plug terminal and earth. The resistance of a glow plug in good condition is very low (less than 1 ohm), so if the test lamp does not light or the continuity tester shows a high resistance, the glow plug is certainly defective. 11 If an ammeter is available, the current draw of each glow plug can be checked. After an initial surge of 15 to 20 amps, each plug should draw approximately 12 amps. Any plug which draws much more or less than this is probably defective. 12 As a final check, the glow plugs can be removed and Inspected as described in the following Section.

Automatic transmission 7B*3
11 When reverse gear Is selected, the control unit keeps the transmission In tow ratio, if this were not the case, it would, In theory, be possible to drive as fast In reverse as in forward gear. 12 An electronic control unit supplies the current to energise the clutch. The control unit receives signals concerning engine speed, road speed, accelerator pedal position, and gear selector position, Sensors include the following. a) Engine rpm sensor (from the Injection/ignition control unit) b) Accelerator pedal switch
c) Throttle valve position sensor d) Selector lever position sensor e) Vehicle speed sensor f) Coolant temperature sensor g) Air conditioning sensor h) Brake switch I) Torque signal
13 The final drive/differential unit Is conventional. Drive from the driven pulley is transmitted to the differential by an Intermediate reduction gear. 14 The ECVT incorporates a warning light which illuminates when a fault occurs.
Precautions 1$ Observe the following precautions to avoid damage to the automatic transmission: a) Do not attempt to start the engine by pushing or towing the car. b) If the car has to be towed for recovery, the distance must not exceed 12 miles (20
km),
and the speed must not exceed
19
mph
(30 kph).
If these conditions cannot be met, or If transmission damage is suspected, only tow the car with the front wheels clear of the ground. c) Only engage P or R when the vehicle is stationary.
1.1b Electromagnetic f Coil 2 Signal from vehicle speed sensor 3 Transmission 4 Electromagnetic powder 5 Drive shaft (driven by crankshaft) $ Transmission input shaft 7 Electromagnetic clutch housing 8 ECVT control unit
clutch control system 9 Accelerator pedal micro switch 10 Throttle
vafve
opening position potentiometer 11 Multifunction switch 12 Ignition switch
13
Air conditioning
signal
14 Engine PPM
signal
15 Accelerator pedal 16 Coolant temperature signal 17 Injection/ignition control unit 18 8attery
1.1c Hydraulic control system 3 Injection/ignition control unit 4 Air conditioner sensor
signal
6 Coolant temperature signal 7 Clutch signal 8 Engine RPM
signal
9 ECVT warning light 10 Selector lever position 11 Accelerator
pedal
switch/throttle
valve
potentiometer/torque signal 12 Brake switch 13
ECVT
control unit 14 Signal from vehicle speed sensor
15
Accelerator pedal position switch
16 Pulley ratio 17 Input shaft RPM 18 Primary oil pressure
19
Primary pulley 20 Electromagnetic clutch 21 Pressure regulating solenoid valve 22 Oil pressure control valve 23 Secondary oil pressure 24 Slip ring 25 Drive from engine 26 Oil pump 27 Vehicle speed sensor 28 Secondary pulley 29 Belt and pulley 30 Drive to drlveshafts

12*2 Body electrical systems
3 Electrical problems usually stem from simple causes, such as loose or corroded connections, a faulty earth connection, a blown fuse, a melted lusible link, or a fautty relay {refer to Section 3 for details of testing relays). Visually inspect the condition of all (uses, wires and connections in a problem circuit before testing the components. Use the wiring diagrams lo determine which terminal connections will need to be checked, in order to pinpoint the trouble-spot. 4 The basic tools required for electrical fault-finding include a circuit tester or voltmeter (a 12-volt bulb with a set of lest leads can also be used for certain tests}; a self-powered test light (sometimes known as a continuity tester); an ohmmeter (to measure resistance): a battery and set of tesi leads: and a lumper wire, preferably with u circuit breaker or fuse incorporated, which can be used to bypass susoect wires or electrical components. Before attempting to locate a problem with tost instruments, use the wiring diagram to determine where to make the connections. 5 To find the source of an intermittent wiring fault (usually due to a poor or dirty connection, or damaged wiring Insulation), a wiggle test can be performed on the wiring. This involves wiggling the wiring by hand, to see if tha fault occurs as the wiring Is moved. It should be possible to narrow down the source of the fault to a particular section of wiring. This method of testing can be used in conjunction with any of the tests descnbed in the following sub-Sections. 6 Apart from problems due to poor connections, two basic types of fault can occur in an electrical circuit - open-circuit, or short-circuit. 7 Open-circuit faults are caused by a break somewhere in the circuit, which prevents current from flowing. An open-circuit fault will prevent a component from working, but will not cause the relevant circuit fuse to blow 8 Short-circuit faults are caused by a shod somewhere in the circuit, which allows Die current flowing In the circuit to escape along an alternative route, usually to earth. Short-circuit faults are normally caused by a breakdown in wiring insulation, which allows a feed wire to touch either another wire, or an earthed component such as the bodysheli. A short-circuit fault will normally cause the relevant circuit fuse to blow.
Finding an open-circuit 9 To check for an opon-circuit, connect one lead of a circuit tester or voltmoter to either the negative battery terminal or a known good earth. 10 Connect the other lead to a connector in the circuit being tested, preferably nearest to the batter/ or luse. 11 Switch on the circuit, bearing In mind that some circuits are live only when tho ignition switch is moved to a particular position. 12 If voltage is present (Indicated either by
3.2 Main fuse box, located on the driver's side of the facie the toster bulb lighting or a voltmeter reading, as applicable), this means that tho section of Ihe circuit between the relevant connector and the battery is problem-free. 13 Continue to check the remainder ot the circuit in the same fashion. 14 When a point is reached at which no voltage Is present, the problem must lie between that point and the previous test point with voltage. Most problems can be traced to a broken, corroded or loose connection.
Finding a short-circuit 15 To check for a short-circuit, first disconnect the load(s) from the circuit (loads are the components which draw current from a circuit, such as bulbs, motors, heating elements, etc). 16 Remove the relevant luse Irom the circuit, and connect a circuit tester or voltmeter to the luse connections. 17 Switch on the circuit, beanng in mind that some circuits are live only when the ignition switch is moved to a particular position. 18 If voltage is present (indicated either by the tester bulb lighting or a voltmeter reading, as applicable), this means that there Is a short-circuit. 19 If no voltage is present, but the fuse still blows with the load(s) connected, this indicates an internal fault in the load(s).
Finding an earth fault 20 The battery negative terminal Is connected to 'earth' - the metal of the engine/transmission and the car body - and
I
IK
J 3.3 To gain access to the fuses, remove the screw and pull the stowage bin away from the facia
most systems are wired so that they only receive a positive feed, the current returning via the metal of Ihe car body. This means that the component mounting and the body form part of that circuit. Loose or corroded mountings can therefore cause a range of electrical faults, ranging from total failure ot a circuit, to a puzzling partial fault. In particular, lights may shine dimly (especially when another circuit sharing the same earth port In operation), motors (eg wiper motors v Ihe radiator cooling fan motor) may run slowly, and Ihe operation of one circuit may have an apparently-unrelated effect on another. Ncie that on many vehicles, earth straps axe uses between certain components, such as the engine/transmission and the body, usually whore there is no metal-to-metal contact between components, due to flexible rubber mountings, etc. 21 To check whether a component $ properly earthed, disconnect Ihe battery, and connect one lead of an ohmmeter to a kwwi good earth point. Connect the other lead to the wire or earth connection being tested. Tha resistance reading should be zero; if not. check the connection as follows. 22 If an earth connection Is thought to be faulty, dismantle the connection, and clean pack to bare metal both the bodysheli and ite wire terminal or the component earth connection mating surface. Be careful to remove all traces of dirt and corrosion, then use a knife to trim away any palm, so thai a clean metal-to-metal joint Is mads. On reassemoly, tighten the joint fasteners securely: if a wire terminal Is being refitted, use serrated washers between tho terminal and the bodysheli. to ensure a clean and secure connection. When the connection is remade, prevent the onset ot corrosion in the future by applying a coat of petroleum idly
or
stlicone-based grease, or by spraying on (a: regular intervals} a proprietary ignition eoater, or a water-aispersant lubneant.
3 Fuses and relays -general information
Fuses 1 Fuses are designod to break a circuit when a predetermined current is reached, in order to protect the components and wiring wttioh could be damaged by excessive current How. Any excessive current flow will be due to a fault in the circuit, usually a short-circuit (see Section 2). 2 The main fuses are located in the fusefcox on the driver's side of the facia (see illustration). 3 To gain access to the fuses, remove tne screw and pull the stowage bin moulding away from the facia (see illustration). 4 Additional fuses and circuit-breakers are located In the engine compartment, and in an