1983 FIAT UNO spark plugs

Ignition unit
36This comprises four elements (photo).
a) Power module - receives the ignition
advance command and controls the
conduction angle of the primary current
and energy stored in the coil.
b) Dissipater plate - eliminates the heat
which is generated by the high volume of
current.
c) Ignition coil with low primary resistance.
d) Distributor - a means of distributing high
tension to the spark plugs. The rotor is
driven in an anti-clockwise direction
(viewed from transmission) by a dog on
the end of the camshaft.
37The system incorporates a safety
pressure switch, which cuts out the ignition if
the turbocharging pressure exceeds a value
of between 0.84 and 0.93 bars (12.2 and
13.5 lbf/in
2) above atmospheric pressure.
Distributor (Microplex) -
removal and refitting#
38Remove the distributor cap and place it to
one side, complete with spark plug leads
(photo).
39Turn the crankshaft by means of the
pulley nut, or by raising and turning a front
wheel with top gear engaged, until No. 4
piston is on its firing stroke. This will be
indicated when the contact end of the rotorarm is aligned with the mark on the distributor
body rim, and the lug on the crankshaft pulley
is aligned with the timing pointer on the
engine. The right-hand underwing shield will
have to be removed in order to see the marks
(photo).
40Unscrew the distributor fixing nuts and
withdraw the distributor.
41When fitting the distributor, the offset
drive dog will automatically locate the
distributor rotor in its correct position, but the
distributor body may require rotating in order
to align the rim mark with the rotor. The
elongated slots for the fixing studs are to
permit initial alignment, not for subsequent
adjustment, as advance angle alterations are
carried out automatically by the system ECU
(photos).
42Tighten the nuts and refit the cap with
leads.
43Unless a stroboscope and a vacuum
pressure gauge are available, it will not be
possible to check the advance values with the
engine running. Where these instruments are
available, connect the vacuum gauge to the
inlet manifold, and the stroboscope in
accordance with the equipment manufac-
turer’s instructions. Refer to Fig. 13.79
according to the inlet manifold vacuum
pressure indicated.
Microplex ignition system
components - testing ª
44An ohmmeter and a voltmeter will be
required for these tests.
45Remove the multipin plug from the ECU.
Engine speed sensor
46Insert the probes of an ohmmeter
between terminals 3 and 16 of the multipin
connector; 618 to 748 ohms (1301 cc) or
578 to 782 ohms (1372 cc) should be
indicated.
47If necessary, carry out a check of the gap
between the sensor and flywheel teeth as
described in Chapter 4, Section 10.
Supplement: Revisions and information on later models 13•89
10.39 Crankshaft pulley timing marks
(arrowed)10.38 Removing the distributor cap10.36 Ignition coil (1) and power module (2)
on 1301 cc Turbo ie engine
Fig. 13.78 Rotor aligned with distributor
body rim mark - Microplex ignition system
(Sec 10)
10.41A Distributor body showing elongated
slots in the mounting lugs
Fig. 13.77 Crankshaft pulley timing mark
aligned with timing pointer - Microplex
ignition system (Sec 10)
1 TDC sensor10.41B Distributor drive dog
13

advance points than the earlier system.
Comparison of Fig. 13.82 with Fig. 4.2
illustrates the difference in layout. Note that
the distributor is mounted on the rear end of
the cylinder head and is driven by the
camshaft.
63When working on the Digiplex 2 ignition
system or associated components, the
precautionary notes outlined in Section 9 of
Chapter 4 must be adhered to.
64As with the earlier system, test
procedures possible on the Digiplex 2 system
are restricted due to the need for specialised
testing equipment. The following checks are
possible, however, using a conventional test
meter.
Ignition coil check
65To check the resistance of the coil’s
primary windings, connect the probes of an
ohmmeter between the positive terminal and
the negative terminal as shown in Fig. 13.83,
and check that the resistance reading at 18 to
28ºC is 0.45 ohms ± 10% (photo).66To check the resistance of the coil’s
secondary windings, connect the probes of an
ohmmeter between the positive terminal and
the HT lead terminal as shown in Fig. 13.84.
Check that the resistance reading at 18 to
28ºC (64 to 82ºF) is 4800 ohms ± 10%.
Ignition timing check
67Refer to paragraph 2 in this Section.
Engine speed and TDC sensor check
68To check the resistance between the
sensor and the ECU, detach the wiring
connector (photo). Connect the probes of an
ohmmeter to the connector terminals and
check that the resistance reading is between
600 and 760 ohms at 20ºC (68ºF). If the
reading is not as specified, the sensor must
be renewed.
69The gap between the sensor and the pins
on the rear face of the flywheel must be
between 0.2 and 0.8 mm. Any deviation
outside of this clearance will be due to
mechanical damage to the sensor andnecessitates its renewal. The sensor is
accurately positioned during manufacture and
secured with tamperproof screws; it does not
require any adjustment during servicing. If it is
necessary to renew the sensor, a special gap
setting tool is required and the task is
therefore best entrusted to a FIAT dealer.
Supplement: Revisions and information on later models 13•91
Fig. 13.82 Digiplex 2 ignition system wiring circuits and components (Sec 10)
10.68 ECU location on the 1372 cc ie
engine10.65 Ignition coil and connections on the
1372 cc ie engineFig. 13.84 Test connections for ignition
coil secondary windings check - Digiplex 2
ignition system (Sec 10)
Fig. 13.83 Test connections for ignition
coil primary windings check - Digiplex 2
ignition system (Sec 10)
13
1 Connection point (lines connected to
the intake manifold)
2 ECU
3 Ignition coil
4 Distributor
5 Engine flywheel (with
five pins)
6 On/off switch (if fitted)
for advance reduction
7 On/off switch 2 (if fitted)
for curves
8 Battery
9 Spark plugs
10 Tachometer
11 Diagnostic socket
12 Engine speed and TDC sensor
13 To check actuator idle speed
14 To terminal no. 1 of injection control unit
(rpm signal)

11 Clutch
Clutch pedal - adjustment
(cable clutch)
Á
1The method of adjusting the clutch has
been revised.
2Fully depress the clutch pedal two or three
times.
3Using a suitable measuring stick placed in
contact with the floor panel (carpet peeled
back), measure dimension “X” in Fig. 13.87.
This dimension must be taken between the
centre of the pedal pad and the floor, first withthe pedal in the fully depressed position, and
then in the fully released position.
4The dimension measured should fall within
the range quoted in the Specifications for this
Supplement.
5Any adjustment which may be required
should be carried out by slackening the
locknut on the cable at the release lever (on
top of the gearbox) and turning the adjusting
nut. Tighten the locknut on completion.
Hydraulic clutch - description
6Some later models are fitted with an
hydraulically operated clutch in place of the
cable operated type. The main components of
the system are a master cylinder, with
separate hydraulic fluid reservoir, and the
operating cylinder. The master cylinder is
Distributor (Digiplex Z) -
removal and refitting#
70Proceed as described in paragraphs 14
to 21. When refitting the distributor, ensure that
the engine is still set at the TDC position. Engage
the rotor arm into position on the shaft so that its
lug engages in the slot in the top end of the drive
spindle. Align the rotor arm with the reference
slot on the edge of the distributor housing as
shown in Fig. 13.85, then fit the distributor into
position and secure with the retaining nuts
(photo). As previously mentioned, the fine timing
is made automatically through the ECU.
Spark plugs and HT leads -
general
71Copper-cored spark plugs are now fitted
to all models. The recommended types are
given in the Specifications Section of this
Supplement.72The HT lead connection sequence to the
distributor cap on the 999 and 1108 cc
engines is shown in Fig. 13.86. That for the
1301 cc Turbo ie is as shown (photo).
13•92 Supplement: Revisions and information on later models
Fig. 13.87 Clutch pedal adjustment
diagram - cable clutch (Sec 11)
For dimension “X” , refer to Specifications
Fig. 13.86 HT lead connections on distributor cap of the 999 and 1108 cc engines (Sec 10)
Fig. 13.85 Rotor arm must align with
slot (1) in distributor housing when refitting
distributor - Digiplex 2 ignition system
(Sec 10)
10.72 HT lead connecting sequence on the
1301 cc Turbo ie engine10.70 Ignition distributor and HT lead
connections on the 1372 cc ie engine
Fault finding - Microplex ignition system
Starter motor turns but engine will not start
m mExcessive TDC sensor gap
m mEngine speed or TDC sensors short-circuited
m mFaulty ECU
m mECU multipin contacts corroded
m mDefective ignition coil
m mDefective ignition switch
m mECU terminal 8 cable faulty
Engine firing on three cylinders
m
mFaulty spark plug
m mDistributor cap cracked
m mFaulty HT cable
Loss of power, excessive fuel consumption
m
mTDC sensor incorrectly located
m mFault in ECU advance angle facility

Fault FindingREF•9
REF
Introduction
The vehicle owner who does his or her own
maintenance according to the recommended
schedules should not have to use this section
of the manual very often. Modern component
reliability is such that, provided those items
subject to wear or deterioration are inspected
or renewed at the specified intervals, sudden
failure is comparatively rare. Faults do not
usually just happen as a result of sudden
failure, but develop over a period of time.
Major mechanical failures in particular are
usually preceded by characteristic symptoms
over hundreds or even thousands of miles.
Those components which do occasionally fail
without warning are often small and easily
carried in the vehicle.
With any fault finding, the first step is to
decide where to begin investigations.
Sometimes this is obvious, but on other
occasions a little detective work will be
necessary. The owner who makes half a
dozen haphazard adjustments or
replacements may be successful in curing a
fault (or its symptoms), but he will be none the
wiser if the fault recurs and he may well have
spent more time and money than was
necessary. A calm and logical approach will
be found to be more satisfactory in the long
run. Always take into account any warning
signs or abnormalities that may have been
noticed in the period preceding the fault –
power loss, high or low gauge readings,
unusual noises or smells, etc – and remember
that failure of components such as fuses or
spark plugs may only be pointers to some
underlying fault.
The pages which follow here are intended
to help in cases of failure to start or
breakdown on the road. There is also a Fault
Diagnosis Section at the end of each Chapter
which should be consulted if the preliminary
checks prove unfruitful. Whatever the fault,
certain basic principles apply. These are as
follows:Verify the fault. This is simply a matter of
being sure that you know what the symptoms
are before starting work. This is particularly
important if you are investigating a fault for
someone else who may not have described it
very accurately.
Don’t overlook the obvious. For example,
if the vehicle won’t start, is there petrol in the
tank? (Don’t take anyone else’s word on this
particular point, and don’t trust the fuel gauge
either!) If an electrical fault is indicated, look
for loose or broken wires before digging out
the test gear.
Cure the disease, not the symptom.
Substituting a flat battery with a fully charged
one will get you off the hard shoulder, but if
the underlying cause is not attended to,the
new battery will go the same way. Similarly,
changing oil-fouled spark plugs for a new set
will get you moving again, but remember that
the reason for the fouling (if it wasn’t simply an
incorrect grade of plug) will have to be
established and corrected.
Don’t take anything for granted.
Particularly, don’t forget that a ‘new’
component may itself be defective (especially
if it’s been rattling round in the boot for
months), and don’t leave components out of a
fault diagnosis sequence just because they
are new or recently fitted. When you do finally
diagnose a difficult fault, you’ll probably
realise that all the evidence was there from
the start.
Electrical faults
Electrical faults can be more puzzling than
straightforward mechanical failures, but they
are no less susceptible to logical analysis if
the basic principles of operation are
understood. Vehicle electrical wiring exists in
extremely unfavourable conditions – heat,
vibration and chemical attack and the first
things to look for are loose or corroded
connections and broken or chafed wires,especially where the wires pass through holes
in the bodywork or are subject to vibration.
All metal-bodied vehicles in current
production have one pole of the battery
‘earthed’, ie connected to the vehicle
bodywork, and in nearly all modern vehicles it
is the negative (–) terminal. The various
electrical components – motors, bulb holders,
etc – are also connected to earth, either by
means of a lead or directly by their mountings.
Electric current flows through the component
and then back to the battery via the
bodywork. If the component mounting is
loose or corroded, or if a good path back to
the battery is not available, the circuit will be
incomplete and malfunction will result. The
engine and/or gearbox are also earthed by
means of flexible metal straps to the body or
subframe; if these straps are loose or missing,
starter motor, generator and ignition trouble
may result.
Assuming the earth return to be
satisfactory, electrical faults will be due either
to component malfunction or to defects in the
current supply. Individual components are
dealt with in Chapter 9. If supply wires are
broken or cracked internally this results in an
open-circuit, and the easiest way to check for
this is to bypass the suspect wire temporarily
with a length of wire having a crocodile clip or
suitable connector at each end. Alternatively,
a 12V test lamp can be used to verify the
presence of supply voltage at various points
along the wire and the break can be thus
isolated.
If a bare portion of a live wire touches the
bodywork or other earthed metal part, the
electricity will take the low-resistance path
thus formed back to the battery: this is known
as a short-circuit. Hopefully a short-circuit will
blow a fuse, but otherwise it may cause
burning of the insulation (and possibly further
short-circuits) or even a fire. This is why it is
inadvisable to bypass persistently blowing
fuses with silver foil or wire.

Engine fails to turn when starter
operated
m mFlat battery (recharge use jump leads or
push start)
m mBattery terminals loose or corroded
m mBattery earth to body defective
m mEngine earth strap loose or broken
m mStarter motor (or solenoid) wiring loose or
broken
m mIgnition/starter switch faulty
m mMajor mechanical failure (seizure)
m mStarter or solenoid internal fault (see
Chapter 12)
Starter motor turns engine slowly
m mPartially discharged battery (recharge, use
jump leads, or push start)
m mBattery terminals loose or corroded
m mBattery earth to body defective
m mEngine earth strap loose m mStarter motor (or solenoid) wiring loose
m mStarter motor internal fault (see Chapter 9)
Starter motor spins without
turning engine
m mFlywheel gear teeth damaged or worn
m mStarter motor mounting bolts loose
Engine turns normally but fails to
start
m mDamp or dirty HT leads and distributor cap
(crank engine and check for spark)
m mNo fuel in tank (check for delivery at
carburettor) m mExcessive choke (hot engine) or insufficient
choke (cold engine)
m mFouled or incorrectly gapped spark plugs
(remove, clean and regap)
m mOther ignition system fault (see Chapter 4)
m mOther fuel system fault (see Chapter 3)
m mPoor compression (see Chapter 1)
m mMajor mechanical failure (eg camshaft drive)
Engine fires but will not run
m
mInsufficient choke (cold engine)
m mAir leaks at carburettor or inlet manifold
m mFuel starvation (see Chapter 3)
m mIgnition fault (see Chapter 4)
Engine will not start
REF•10Fault Finding
Spares and tool kit
Most vehicles are supplied only with
sufficient tools for wheel changing; the
Maintenance and minor repairtool kit detailed
in Tools and working facilities,with the
addition of a hammer, is probably sufficient
for those repairs that most motorists would
consider attempting at the roadside. In
addition a few items which can be fitted
without too much trouble in the event of a
breakdown should be carried. Experience and
available space will modify the list below, but
the following may save having to call on
professional assistance:
m mSpark plugs, clean and correctly gapped
m mHT lead and plug cap – long enough to
reach the plug furthest from the distributor
m mDistributor rotor, condenser and contact
breaker points (where applicable)m mDrivebelt(s) — emergency type may
suffice
m mSpare fuses
m mSet of principal light bulbs
m mTin of radiator sealer and hose bandage
m mExhaust bandage
m mRoll of insulating tape
m mLength of soft iron wire
m mLength of electrical flex
m mTorch or inspection lamp (can double as
test lamp)
m mBattery jump leads
m mTow-rope
m mIgnition waterproofing aerosol
m mLitre of engine oil
m mSealed can of hydraulic fluid
m mEmergency windscreen
m mWormdrive clips
m mTube of filler pasteIf spare fuel is carried, a can designed for
the purpose should be used to minimise risks
of leakage and collision damage. A first aid kit
and a warning triangle, whilst not at present
compulsory in the UK, are obviously sensible
items to carry in addition to the above. When
touring abroad it may be advisable to carry
additional spares which, even if you cannot fit
them yourself, could save having to wait while
parts are obtained. The items below may be
worth considering:
m mClutch and throttle cables
m mCylinder head gasket
m mAlternator brushes
m mTyre valve core
One of the motoring organisations will be
able to advise on availability of fuel, etc, in
foreign countries.
A simple test lamp is useful for checking
electrical faultsCarrying a few spares may save you a long walk!

Buying spare parts
Spare parts are available from many
sources, for example, FIAT garages, other
garages and accessory shops, and motor
factors. Our advice regarding spare parts is as
follows:
Officially appointed FIAT garages -This is
the best source of parts which are peculiar to
your car and otherwise not generally available
(eg complete cylinder heads, internal gearbox
components, badges, interior trim etc). It is
also the only place at which you should buy
parts if your vehicle is still under warranty;
non-FlAT components may invalidate the
warranty. To be sure of obtaining the correct
parts it will always be necessary to give the
partsman your car’s engine number, chassis
number and number for spares, and if
possible, to take the old part along for positive
identification. Many parts are available under
a factory exchange scheme - any parts
returned should always be clean. It obviously
makes good sense to go straight to the
specialists on your car for this type of part for
they are best equipped to supply you. They
will also be able to provide their own FIATservice manual for your car should you require
one.
Other garages and accessory shops - These
are often very good places to buy material
and components needed for the maintenance
of your car (eg oil filters, spark plugs, bulbs,
drivebelts, oils and grease, touch-up paint,
filler paste etc). They also sell accessories,
usually have convenient opening hours,
charge lower prices and can often be found
not far from home.
Motor factors - Good factors stock all of the
more important components which wear out
relatively quickly (eg clutch components,
pistons, valves, exhaust systems, brake
pipes/seals/shoes and pads etc). Motor
factors will often provide new or reconditioned
components on a part exchange basis - this
can save a considerable amount of money.
Vehicle identification
numbers
Modifications are a continuing and
unpublicised process in vehicle manufacture
quite apart from major model changes. Spareparts manuals and lists are compiled upon a
numerical basis, the individual vehicle
numbers being essential to correct identifi-
cation of the component required.
The chassis type and number plate is
located on the wing valance under the bonnet.
The identification data plate is located on the
radiator top rail. The engine type and number
is stamped on the cylinder block. The
paintwork colour code is given on a label
stuck to the inner surface of the tailgate.
REF•12Buying spare parts & Vehicle identification numbers
Manufacturer’s plate legend
Location of under-bonnet identification numbers and plates
A Chassis type and number
B Manufacturer’s plate
C Engine number (903 cc)
D Engine number (1116 cc and 1301 cc)
Engine number on 1116 cc engine
A Name of manufacturer
B Approval number
C Vehicle identification number
D Chassis serial number
E Maximum laden weight
F Maximum laden weight
(vehicle plus trailer)G Maximum front axle weight
H Maximum rear axle weight
I Engine type
L Body type
M Spares reference
N Diesel models only (smoke
coefficient)

S
Safety first -0•5
Safety pressure switch - 13•90
Scalding -0•5
Scratches in bodywork - 12•2
Screw threads and fastenings - REF•8
Seat belts - 12•10, REF•2
Seats - 12•9, REF•2
Servo unit -8•8, 13•103
Shock absorbers - 11•4, REF•2, REF•3
Shoes -8•3
Side light -9•7
Side repeater lamp -9•7
Spares - REF•10, REF•12
Spark plugs -4•7, 13•92
Speedometer -9•8
Spotlamp - 13•108
Springs - 11•3, 11•4, REF•3
Starter motor -9•4, 13•104, 13•105
Starter fault -1•35, 9•14, 13•92, REF•10
Steering-9•5, 10•1et seq, 13•106, REF•1,
REF•2, REF•3
Steering fault finding - 10•4
Stop lamp switch -8•9
Struts - 11•2, 13•111
Sump -1•11, 1•22, 1•26, 1•31, 13•19,
13•24, 13•46, 13•53
Sunroof - 12•12
Supplement: Revisions and information on
later models- 13•1et seq
Supplementary air valve - 13•67, 13•69,
13•71, 13•80
Suspension- 11•1et seq, 13•111, REF•2,
REF•3
Suspension fault finding - 11•6
Switches -2•3, 4•8, 8•9, 9•5, 13•69, 13•72,
13•80, 13•90, 13•106 to 13•109
T
Tailgate -9•6, 12•8, 12•9, 13•112
TDC sensor -4•7, 13•90, 13•91
Thermostat -2•3, 13•54, 13•57
Throttle control linkage - 13•72
Throttle position switch - 13•69, 13•72,
13•80
Throttle valve housing - 13•67, 13•70,
13•80
Tie-rod - 10•2
Timing -4•4, 13•85, 13•91
Timing belt -1•24, 1•29, 1•32, 13•20,
13•30, 13•35, 13•38, 13•53
Timing chain -1•9, 1•19, 1•22
Tools - REF•5, REF•7, REF•8, REF•10
Towing -0•8
Track control arm - 11•4
Trailing arms - 11•5
Transmission-1•13, 1•22, 1•27, 1•32, 6•1
et seq, 13•26, 13•33, 13•36, 13•49,
13•53, 13•94, 13•96
Transmission fault finding -6•4
Transmission oil -0•6, 0•13, 6•1, 13•14,
13•95
Trim panels - 12•5, 13•114
Trip master - 13•108
Tripode joint -7•3
Turbocharger - 13•82, 13•83
Turbocharger fault finding - 13•84
Tyres -7•5, 10•4, 11•6, REF•4
U
Underframe - 12•1
Unleaded fuel - 13•60
Upholstery - 12•2
V
Vacuum sensor - 13•86
Vacuum servo -8•8, 13•103
Valve clearances -1•9, 1•23, 1•32, 13•20,
13•37
Vehicle identification - REF•2, REF•12
Voltage regulator -9•4
W
Washer system -9•10, 13•110
Water pump -2•4, 13•55, 13•58
Weights -0•6, 13•17
Wheel alignment - 10•3
Wheel bearings -7•3, 7•4, REF•3
Wheel changing -0•8
Wheel cylinder -8•4
Wheels -7•5, REF•4
Window regulator - 12•7
Windows -9•11, 12•6, 12•9, 13•109,
13•113
Windscreen - 12•8, REF•1
Wings - 12•5
Wiper blade and arm -9•9
Wiper motor -9•9, 9•10, 13•109, 13•110
Wiper fault -9•14
Wiring diagrams- 14•1et seq
Working facilities - REF•7
IndexREF•19
REF