1983 FIAT UNO check engine

47Loosen off the switch-to-column clamp
screw, disconnect the wiring connectors to
the switch and withdraw the switch from the
column (photos).
48Refit in the reverse order of removal, but
ensure that the lug of the switch aligns with
the slot in the column as it is fitted into
position. Check for satisfactory operation of
the switches on completion.
Instrument panel
(Turbo ie models) -
removal and refitting
Á
49The instrument panel on these models
incorporates an engine oil pressure gauge
and a turbo boost gauge. The latter is
connected directly to the inlet manifold.
50Apart from disconnecting the boost gauge
rubber hose, the instrument panel removal
and refitting procedure is as described in
Chapter 9 for the 1301 cc model or from
paragraph 57 in this Section for the 1372 cc
model.
51A digital electronic instrument panel is
available as an option on Turbo ie models.
The removal and refitting procedures differ
from analogue instrument panels in respect of
the electrical connections - a speedometer
drive cable is not used.
Facia-mounted switches
(1301 cc Turbo ie model) -
removal and refitting
Á
52Disconnect the battery.53Insert a thin-bladed screwdriver into the
joint between the switch block and the switch
block housing, to depress the plastic retaining
tabs. Do this carefully, otherwise the switch
block or casing will be damaged.
54Withdraw the switch block. Individual
switches can now be pushed out of the block.
Fibre optics are used to illuminate some
switches, these simply pull out of their
sockets (photos). The illumination bulb is
located on a crossmember found behind the
instrument pack. Removal of instruments/top
cover allows access.
55The switch housing can be removed after
extracting the fixing screws (photos).
56Refitting is a reversal of removal.
Instrument panel
(later models) -
removal and refitting
Á57Disconnect the battery negative lead.
58Unscrew and remove the two instrument
panel-to-facia retaining screws (photo).
59Remove the lower facia trim panel, which
is secured by two screws and a nut. Reach up
to the rear of the instrument panel to
disconnect the speedometer cable, then push
the panel from its recess in the facia.
Disconnect the multi-connectors from the rear
face of the panel and withdraw it (photo).
60Refit in the reverse order of removal.
Ensure that the speedometer cable is fully
engaged as the unit is refitted into position.
Supplement: Revisions and information on later models 13•107
15.47B . . . and remove the column switch15.47A Undo the retaining screw . . .15.45C . . . and the lower column
shroud . . .
15.58 Remove the retaining screws . . .15.55B Facia switch housing inner screw
removal on the 1031 cc Turbo ie model
15.54B Disconnecting a fibre optic cable
from its holder on the 1301 cc Turbo ie
model15.54A Switch block withdrawal on the
1301 cc Turbo ie model
15.55A Facia switch housing lower screw
removal on the 1301 cc Turbo ie model
13

Auxiliary control panel
(later models) -
removal and refitting
Á
61Disconnect the battery negative lead.
62Insert the flat of a screwdriver under the
trim piece at the end of the auxiliary panel as
shown and prise it free. Repeat the procedure
and remove the trim piece at the other end of
the panel (photo).
63Undo the retaining screws, withdraw the
panel from the facia. Disconnect the wiring
connectors from the panel switches to
remove the panel completely (photo).
64A switch bulb can be renewed by
untwisting the holder and removing the holder
and bulb.
65A switch unit can be removed from the
panel by unscrewing the four retaining screws.66Refitting is a reversal of the removal
procedure. Ensure that the wiring connections
are securely made and check for satisfactory
operation of the switches on completion.
Heater control panel
(later models) -
removal and refitting
Á
67Disconnect the battery negative lead.
68Pull free the heater/fresh air and blower
control knobs (photo).
69Undo the two retaining screws and
withdraw the control panel from the facia
(photos). Detach the wiring connectors from the
panel illumination lights and remove the panel.
70Refitting is a reversal of the removal
procedure. Ensure that the wiring connections
are securely made and on completion check
that the operation of the controls is satisfactory.
Trip master Á
71This electronic instrument is fitted into the
check panel of 1100SL and 1300SL models
from 1986.
72The device provides information on fuel
consumption, range, speed and elapsed time.
73With the ignition key turned to MAR,
figures are displayed in respect of the last
journey - average fuel consumption, average
speed and elapsed time (up to switching off
the ignition).
74As soon as the engine is started, the
instrument processes the current values to
include fuel consumption, range and the
actual time. 75Fuel consumption is only displayed when
the road speed exceeds 8.0 km/h (5.0 mph).
76The fuel range is only displayed after a
road speed of between 25.0 and 70.0 km/h
(15.0 to 44.0 mph) has been maintained for at
least 90 seconds or at higher speeds for
22 seconds.
77A reset button is provided, also a display
change button (from instant to average or
total values). Should the instrument reading
exceed 99 hours, 59 minutes or 1000 km
(622 miles) depressing the display change
button will display all zeros. Depress button E
to resume normal function.
78Refer to the end of the manual for a wiring
diagram of the check panel, incorporating the
trip master.
Interior roof mounted spotlamp,
switch and/or clock -
removal and refitting
Á
79Disconnect the battery negative lead.
80Prise free the lamp unit from its aperture
in the roof panel using a thin-bladed
screwdriver. The lamp bulb can be inspected
by untwisting the holder and withdrawing it
from the rear of the unit (photos). Extract the
bulb from the holder if it requires renewal.
81To remove the lamp switch from the
panel, reach through the lamp aperture and
press it free from the roof panel (photo).
Detach the wiring connectors.
82To remove the clock, reach through the
lamp aperture and undo the retaining screws
(photo). Withdraw the clock and detach the
wiring connectors.
13•108 Supplement: Revisions and information on later models
15.69B . . . and withdraw the heater control
panel15.69A . . . undo the retaining screws
(arrowed)15.68 Remove the control knobs . . .
15.63 . . . and withdraw the auxiliary
control panel
15.62 Prise free the trim covers for access
to retaining screws . . .15.59B . . . and disconnect the
speedometer cable15.59A . . . withdraw the instrument
panel . . .

As it is lifted, invert it and detach the washer
hose from the washer nozzle (photos).
97Where applicable, detach and remove the
washer reservoir from the recess in the front
of the windscreen to allow access to the wiper
motor.
98Unscrew and remove the two wiper motor
retaining screws. Lower and withdraw the
unit, then detach the cover from the motor.
Disconnect the wiring from the wiper motor
and withdraw it from the car (photos).
99Refit in the reverse order of removal.
Check for satisfactory operation of the wiper
and washer on completion.
Windscreen washer reservoir
(Turbo ie models) -
removal and refitting
Á
100Disconnect the battery negative lead.
101Remove the bonnet as described in
Chapter 12.
102Remove the wiper arm and blade as
described in Chapter 9, then unscrew and
remove the pivot nut.
103Undo the air inlet grille retaining screws
noting that two are not fitted with washers.
Where applicable, remove the washer
reservoir filler cap from the reservoir neck
protruding through the grille. Carefully prise
free and lift the air inlet grille clear of the body.
As it is lifted, invert it and detach the washer
hose from the washer nozzle.
104Syphon any remaining washer fluid from
the reservoir, then disconnect it and partiallywithdraw it from the recess in front of the
windscreen so that the wiring connection and
the washer supply hoses (to the windscreen
washer and the rear screen washer nozzles)
can be detached from the pump unit. Remove
the reservoir from the vehicle.
105Refit in the reverse order of removal. If the
washer pump unit was detached from the
reservoir, use a new seal washer when refitting
it. Top up the reservoir and check the screen
washers for satisfactory operation before
refitting the grille panel and the wiper arm/blade.
Tailgate wiper motor
(later models) -
removal and refitting
Á
106Although the tailgate wiper motor differs
in appearance, its removal and refitting
procedures are much the same as those
described for the earlier models in Section 27
of Chapter 9 (photo).
Radio
107All later models are now equipped with
power supply and speaker leads for radio
installation.
108Installation of the standard FIAT aerial
mounted on the windscreen pillar is shown
(photos).
Check control system sensors -
description
109The locations of the sensors referred to in
Chapter 9, Section 34 are given in the
following paragraphs, and their construction
differs according to their individual function.
Brake fluid level sensor
110This is mounted in the master cylinder
fluid reservoir cap, and comprises a pair of
reed switches in a glass bulb, and a magnet at
the end of a float.
111When the fluid level is correct, the
magnetic flux closes the switches. In the
event of a leak in the system, the magnet
moves away, the switches open and the
warning lamp comes on.
Brake disc pad wear sensor
112This is basically a circuit wire embedded
in the pad friction material. As the pad wears,
the wire is eventually exposed and contacts
the disc, whereupon the warning lamp comes
on to indicate that pad renewal is necessary.
Coolant level sensor
113This is located in the cooling system
expansion tank, and is of the reed switch
type, which operates in a similar way to that
described for the brake fluid sensor.
Engine oil level sensor
114This is located at the end of the dipstick,
and comprises a pair of switches at the end of a
bi-metallic strip, heated by electrical resistance.
115The heat is dissipated by the immersion
of the dipstick in the engine oil, so preventing
the bi-metallic strip from curving so much that
the switches would open.
116If the oil level drops, the heat is no longer
dissipated, the switches open, and the
warning lamp comes on.
13•110 Supplement: Revisions and information on later models
15.108B Pillar lower screw for aerial15.108A Pillar upper screws for aerial15.106 Tailgate wiper motor - later model
15.98C . . . and detach the wiring
connector15.98B . . . separate the wiper motor from
its cover . . .15.98A Remove the wiper motor retaining
screws . . .

Door closure sensor
117The sensor consists of a microswitch
within the lock. The switch actuates the
warning lamp according to whether the lock is
in the open or closed mode.
Check control system sensors -
testing
Brake fluid level sensor
118With the fluid level correct, switch on the
ignition and depress the centre of the
reservoir cap. If the sensor switches are
working correctly, then “FAULT” should be
indicated on the check panel.
Coolant level sensor
119With the coolant level in the expansion
tank correct, switch on the ignition and then
pull the wiring plug from the sensor. “FAULT”
should be indicated on the check panel. If it is
not, then it is the panel which is faulty.
120An ohmmeter should be used to check
for continuity, holding the float in both the full
and low level positions.
Engine oil level sensor
121With the oil level correct, disconnect the
wiring plug from the dipstick, and then bridge
the plug terminals (not dipstick side) with a 12
ohm resistor. Switch on the ignition.
122If the red light on the check panel goes
out, then the fault is due to the sensor.
123If the light stays on, then it is the check
panel module which is faulty.
Door closure sensor
124Any fault in the lock microswitch can best
be detected using an ohmmeter.
16 Suspension
Front anti-roll bar -
removal and refittingª
1A front anti-roll bar is fitted to the 1301 cc,
1372 cc ie and 1372 cc Turbo ie engined
models. Removal of the bar on all models isas follows. Firstly loosen off the front
roadwheel bolts, then raise the front of the
car, securely support it on axle stands and
remove the front roadwheels.
2Disconnect the two gearchange rods from
the transmission.
3Unbolt and disconnect the anti-roll bar
insulating clamps from the floorpan (photo).
4Unbolt the end links from the track control
arms and withdraw the anti-roll bar (photo).
5Refitting is a reversal of removal, but only
tighten the nuts and bolts to the specified
torque with the car parked on level ground,
with four passengers and 40 kg of luggage
inside.
Suspension strut - later models
6The suspension strut upper mounting nuts
on later models also secure the brackets for
the mounting of ancillary components such as
the fuel filter, fuel system relays and fuses,
etc. (depending on model).
7When removing the suspension strut units,
it will therefore be necessary to detach and
support these brackets and their fittings
(photo).
17 Bodywork
Plastic components
1With the use of more and more plastic
body components by the vehicle
manufacturers (e.g. bumpers, spoilers, and in
some cases major body panels), rectification
of more serious damage to such items has
become a matter of either entrusting repair
work to a specialist in this field, or renewing
complete components. Repair of such
damage by the DIY owner is not really
feasible owing to the cost of the equipment
and materials required for effecting such
repairs. The basic technique involves making
a groove along the line of the crack in the
plastic using a rotary burr in a power drill. The
damaged part is then welded back togetherby using a hot air gun to heat up and fuse a
plastic filler rod into the groove. Any excess
plastic is then removed and the area rubbed
down to a smooth finish. It is important that a
filler rod of the correct plastic is used, as
body components can be made of a variety
of different types (e.g. polycarbonate, ABS,
polypropylene). Damage of a less serious
nature (abrasions, minor cracks, etc.) can be
repaired by the DIY owner using a two-part
epoxy filler repair material. Once mixed in
equal proportions, this is used in similar
fashion to the bodywork filler used on metal
panels. The filler is usually cured in twenty to
thirty minutes, ready for sanding and
painting.
2If the owner is renewing a complete
component himself, or if he has repaired it
with epoxy filler, he will be left with the
problem of finding a suitable paint for
finishing which is compatible with the type of
plastic used. At one time the use of a
universal paint was not possible owing to the
complex range of plastics encountered in
body component applications. Standard
paints, generally speaking, will not bond to
plastic or rubber satisfactorily. However, it is
now possible to obtain a plastic body parts
finishing kit which consists of a pre-primer
treatment, a primer and coloured top coat.
Full instructions are normally supplied with a
kit, but basically the method of use is to first
apply the pre-primer to the component
concerned and allow it to dry for up to
30 minutes. Then the primer is applied and
left to dry for about an hour before finally
applying the special coloured top coat. The
result is a correctly coloured component
where the paint will flex with the plastic or
rubber, a property that standard paint does
not normally possess.
Rear view mirrors Á
Interior
3The mirror is of safety type, “breaking” off
its ball fixing upon impact from a front seat
occupant.
4To remove the mirror, grip the head and
Supplement: Revisions and information on later models 13•111
16.7 Suspension strut upper mounting
nuts, showing bracket and cable clip on
the 1372 cc ie model16.4 Anti-roll bar fixing nuts (arrowed)16.3 Anti-roll bar clamp
13

Wiring diagrams 14•21
14
Component key for wiring diagrams 30 to 52 (continued)
Note: Not all the items listed will be fitted to all models
No Description
111 Push button on left front pillar for
centre courtesy light
112 Front electric windows switch panel,
driver’s side
113 Join between dashboard cable and
adjustable map reading light cables
114 Join with left front electric window
cables
115 Join between dashboard cable and
rear cables
116 Join between rear cable and courtesy
light cables
117 Left front speaker
118 Handbrake ‘on’ switch
119 Centre courtesy light bulb
119A Adjustable map reading light on rear
view mirror
120 Right front electric window motor
121 Right front central locking geared
motor
122 Switch signalling right front door ajar
123 Push button on right front pillar for
centre courtesy light
124 Electric windows control panel,
passenger side
125 Fuel level gauge
126 Join with right front electric window
cables
127 Join between engine cable and
dashboard cables
128 Right front speaker
129 Left rear light cluster
130 Join between rear cable and luggage
compartment courtesy light
131 Windscreen washer pump wiring join
132 Rear screen washer pump wiring join
133 Left rear earth
134 Rear screen wiper motor
135 Electric fuel pump
136 Rear number plate lamp
137 Heated rear screen
138 Right rear light cluster
139 Rear foglamp go-ahead switch
140 Join between front cable and antiskid
brakes cables
141 Join between front cable and antiskid
brakes cables
142 25 A fuse for antiskid brakes
143 Antiskid braking system control unit
144 Left modulator for antiskid brakes
145 Right modulator for antiskid brakes
146 Sensor on left front wheel
147 Sensor on right front wheel
148 10A fuse for antiskid braking system
149 Vacuum switch for antiskid braking
system
150 Antiskid braking system engagement
relay
151 Antiskid braking system failure
signalling switch
152 Digiplex electronic ignition control
unitNo Description
153 Bosch SPi Mono-Jetronic injection
system control unit
155 Join between engine cable and
injection cables
156 Join between engine cable and rear
cables for SPi system
157 Idle adjustment actuator
158 Throttle position switch
159 Injector current restriction resistor
(SPi)
162 Engine cut-out solenoid
163 Idle cut-out solenoid valve
168 Tachometer electro-magnetic sensor
169 Automatic heater control unit
170 Heater fan
171 Outside temperature sensor
172 Mixed air temperature sensor
173 Air mixture flap electrical control
motor
174 Diagnostic socket for automatic
heater
175 Connector block
176 Connector block
177 Join with cables for automatic heater
178 Radiator coolant circulation solenoid
valve
179 Automatic heater unit:
A Temperature control potentiometer
B Fan speed control potentiometer
C Heater controls light bulbs
D Ideogram signalling automatic
function engaged
E Automatic function engaged
switch
180 Horn
181 Check Panel:
A Insufficient engine oil level warning
light
B Insufficient coolant level warning
light
C Failure with side lights/rear
foglamp/rear number
plate light/braking lights warning light
D Insufficient brake fluid level
warning light
E Door ajar warning light
F Brake pad wear warning light
182 Earth on dashboard
183 Join with cables for central locking
184 Join with cables for central locking
185 Left rear central locking geared motor
186 Right rear central locking geared
motor
187 Contact on choke lever
188 Resistor for inlet manifold heating
189 Pre-heating thermal switch
191 Heated Lambda sensor
192 Lambda sensor protective fuse
193 Silicon diode
194 Join between front cable and injection
cable
197 Connector blockNo Description
198 Rear cable join
199 Insufficient engine oil level sensor
200 Insufficient coolant level sensor
201 Switch signalling left rear door ajar
202 Switch signalling right rear door ajar
203 Switch on gear selector
204 Light for gear selector panel signalling
gear engaged
205 Parking signal not on
206 Connector block
207 Join in engine compartment with
injection cables
208 Petrol vapour cut out-solenoid valve
209 Petrol vapour cut out-solenoid valve
210 Airflow meter
211 Speedometer relay
212 LE2 Jetronic electronic injection
control unit
213 Connector block
214 Connector block
215 Connector block
216 Ignition cable join
217 Join between front cable and
emission control cable
218 Join between front cable and battery
cable
219 Injection system air temperature
sensor
220 Ignition control unit relay feed
225 Front cable join
226 Front cable join
227 Dim-dip circuit cut out switch
228 Dim-dip circuit resistance
229 Dim-dip circuit 7.5 A protective fuse
230 Driver’s side seat heated pad
231 Driver’s seat backrest heated pad
232 10 A protective fuse for driver’s seat
heated pads
233 Foglamps go-ahead switch
234 Driving lights cut out switch
235 Dipped headlamps relay
236 Main beam headlamps relay
237 Join between engine cable and
dashboard cables
Wire colour codes
A Light blue
B White
C Orange
G Yellow
H Grey
L Blue
M Brown
N Black
R Red
S Pink
V Green
Z Violet
Example of two-colour wire:
BN (White/Black)

MOT Test ChecksREF•1
This is a guide to getting your vehicle through the MOT test.
Obviously it will not be possible to examine the vehicle to the same
standard as the professional MOT tester. However, working through
the following checks will enable you to identify any problem areas
before submitting the vehicle for the test.
Where a testable component is in borderline condition, the tester
has discretion in deciding whether to pass or fail it. The basis of such
discretion is whether the tester would be happy for a close relative or
friend to use the vehicle with the component in that condition. If the
vehicle presented is clean and evidently well cared for, the tester may
be more inclined to pass a borderline component than if the vehicle is
scruffy and apparently neglected.
It has only been possible to summarise the test requirements here,
based on the regulations in force at the time of printing. Test standards
are becoming increasingly stringent, although there are some
exemptions for older vehicles. For full details obtain a copy of the Haynes
publication Pass the MOT! (available from stockists of Haynes manuals).
An assistant will be needed to help carry out some of these checks.
The checks have been sub-divided into four categories, as follows:
HandbrakeMTest the operation of the handbrake.
Excessive travel (too many clicks) indicates
incorrect brake or cable adjustment.
MCheck that the handbrake cannot be
released by tapping the lever sideways. Check
the security of the lever mountings.
Footbrake
MDepress the brake pedal and check that it
does not creep down to the floor, indicating a
master cylinder fault. Release the pedal, wait
a few seconds, then depress it again. If the
pedal travels nearly to the floor before firm
resistance is felt, brake adjustment or repair is
necessary. If the pedal feels spongy, there is
air in the hydraulic system which must be
removed by bleeding.MCheck that the brake pedal is secure and in
good condition. Check also for signs of fluid
leaks on the pedal, floor or carpets, which
would indicate failed seals in the brake master
cylinder.
MCheck the servo unit (when applicable) by
operating the brake pedal several times, then
keeping the pedal depressed and starting the
engine. As the engine starts, the pedal will
move down slightly. If not, the vacuum hose or
the servo itself may be faulty.
Steering wheel and column
MExamine the steering wheel for fractures or
looseness of the hub, spokes or rim.
MMove the steering wheel from side to side
and then up and down. Check that the
steering wheel is not loose on the column,
indicating wear or a loose retaining nut.
Continue moving the steering wheel as before,
but also turn it slightly from left to right.
MCheck that the steering wheel is not loose
on the column, and that there is no abnormalmovement of the steering wheel, indicating
wear in the column support bearings or
couplings.
Windscreen and mirrors
MThe windscreen must be free of cracks or
other significant damage within the driver’s
field of view. (Small stone chips are
acceptable.) Rear view mirrors must be
secure, intact, and capable of being adjusted.
1Checks carried out
FROM THE DRIVER’S SEAT
1Checks carried out
FROM THE DRIVER’S
SEAT2Checks carried out
WITH THE VEHICLE
ON THE GROUND3Checks carried out
WITH THE VEHICLE
RAISED AND THE
WHEELS FREE TO
TURN4Checks carried out on
YOUR VEHICLE’S
EXHAUST EMISSION
SYSTEM
REF

MOT Test ChecksREF•3
REF
Exhaust system
MStart the engine. With your assistant
holding a rag over the tailpipe, check the
entire system for leaks. Repair or renew
leaking sections.
Jack up the front and rear of the vehicle,
and securely support it on axle stands.
Position the stands clear of the suspension
assemblies. Ensure that the wheels are
clear of the ground and that the steering
can be turned from lock to lock.
Steering mechanism
MHave your assistant turn the steering from
lock to lock. Check that the steering turns
smoothly, and that no part of the steering
mechanism, including a wheel or tyre, fouls
any brake hose or pipe or any part of the body
structure.
MExamine the steering rack rubber gaiters
for damage or insecurity of the retaining clips.
If power steering is fitted, check for signs of
damage or leakage of the fluid hoses, pipes or
connections. Also check for excessive
stiffness or binding of the steering, a missing
split pin or locking device, or severe corrosion
of the body structure within 30 cm of any
steering component attachment point.
Front and rear suspension and
wheel bearings
MStarting at the front right-hand side, grasp
the roadwheel at the 3 o’clock and 9 o’clock
positions and shake it vigorously. Check for
free play or insecurity at the wheel bearings,
suspension balljoints, or suspension mount-
ings, pivots and attachments.
MNow grasp the wheel at the 12 o’clock and
6 o’clock positions and repeat the previous
inspection. Spin the wheel, and check for
roughness or tightness of the front wheel
bearing.
MIf excess free play is suspected at a
component pivot point, this can be confirmed
by using a large screwdriver or similar tool and
levering between the mounting and the
component attachment. This will confirm
whether the wear is in the pivot bush, its
retaining bolt, or in the mounting itself (the bolt
holes can often become elongated).
MCarry out all the above checks at the other
front wheel, and then at both rear wheels.
Springs and shock absorbers
MExamine the suspension struts (when
applicable) for serious fluid leakage, corrosion,
or damage to the casing. Also check the
security of the mounting points.
MIf coil springs are fitted, check that the
spring ends locate in their seats, and that the
spring is not corroded, cracked or broken.
MIf leaf springs are fitted, check that all
leaves are intact, that the axle is securely
attached to each spring, and that there is no
deterioration of the spring eye mountings,
bushes, and shackles.MThe same general checks apply to vehicles
fitted with other suspension types, such as
torsion bars, hydraulic displacer units, etc.
Ensure that all mountings and attachments are
secure, that there are no signs of excessive
wear, corrosion or damage, and (on hydraulic
types) that there are no fluid leaks or damaged
pipes.
MInspect the shock absorbers for signs of
serious fluid leakage. Check for wear of the
mounting bushes or attachments, or damage
to the body of the unit.
Driveshafts
(fwd vehicles only)
MRotate each front wheel in turn and inspect
the constant velocity joint gaiters for splits or
damage. Also check that each driveshaft is
straight and undamaged.
Braking system
MIf possible without dismantling, check
brake pad wear and disc condition. Ensure
that the friction lining material has not worn
excessively, (A) and that the discs are not
fractured, pitted, scored or badly worn (B).
MExamine all the rigid brake pipes
underneath the vehicle, and the flexible
hose(s) at the rear. Look for corrosion, chafing
or insecurity of the pipes, and for signs of
bulging under pressure, chafing, splits or
deterioration of the flexible hoses.
MLook for signs of fluid leaks at the brake
calipers or on the brake backplates. Repair or
renew leaking components.
MSlowly spin each wheel, while your
assistant depresses and releases the
footbrake. Ensure that each brake is operating
and does not bind when the pedal is released.
3Checks carried out
WITH THE VEHICLE RAISED
AND THE WHEELS FREE TO
TURN

REF•4MOT Test Checks
MExamine the handbrake mechanism,
checking for frayed or broken cables,
excessive corrosion, or wear or insecurity of
the linkage. Check that the mechanism works
on each relevant wheel, and releases fully,
without binding.
MIt is not possible to test brake efficiency
without special equipment, but a road test can
be carried out later to check that the vehicle
pulls up in a straight line.
Fuel and exhaust systems
MInspect the fuel tank (including the filler
cap), fuel pipes, hoses and unions. All
components must be secure and free from
leaks.
MExamine the exhaust system over its entire
length, checking for any damaged, broken or
missing mountings, security of the retaining
clamps and rust or corrosion.
Wheels and tyres
MExamine the sidewalls and tread area of
each tyre in turn. Check for cuts, tears, lumps,
bulges, separation of the tread, and exposure
of the ply or cord due to wear or damage.
Check that the tyre bead is correctly seated
on the wheel rim, that the valve is sound andproperly seated, and that the wheel is not
distorted or damaged.
MCheck that the tyres are of the correct size
for the vehicle, that they are of the same size
and type on each axle, and that the pressures
are correct.
MCheck the tyre tread depth. The legal
minimum at the time of writing is 1.6 mm over
at least three-quarters of the tread width.
Abnormal tread wear may indicate incorrect
front wheel alignment.
Body corrosion
MCheck the condition of the entire vehicle
structure for signs of corrosion in load-bearing
areas. (These include chassis box sections,
side sills, cross-members, pillars, and all
suspension, steering, braking system and
seat belt mountings and anchorages.) Any
corrosion which has seriously reduced the
thickness of a load-bearing area is likely to
cause the vehicle to fail. In this case
professional repairs are likely to be needed.
MDamage or corrosion which causes sharp
or otherwise dangerous edges to be exposed
will also cause the vehicle to fail.
Petrol models
MHave the engine at normal operating
temperature, and make sure that it is in good
tune (ignition system in good order, air filter
element clean, etc).
MBefore any measurements are carried out,
raise the engine speed to around 2500 rpm,
and hold it at this speed for 20 seconds. Allowthe engine speed to return to idle, and watch
for smoke emissions from the exhaust
tailpipe. If the idle speed is obviously much
too high, or if dense blue or clearly-visible
black smoke comes from the tailpipe for more
than 5 seconds, the vehicle will fail. As a rule
of thumb, blue smoke signifies oil being burnt
(engine wear) while black smoke signifies
unburnt fuel (dirty air cleaner element, or other
carburettor or fuel system fault).
MAn exhaust gas analyser capable of
measuring carbon monoxide (CO) and
hydrocarbons (HC) is now needed. If such an
instrument cannot be hired or borrowed, a
local garage may agree to perform the check
for a small fee.
CO emissions (mixture)
MAt the time of writing, the maximum CO
level at idle is 3.5% for vehicles first used after
August 1986 and 4.5% for older vehicles.
From January 1996 a much tighter limit
(around 0.5%) applies to catalyst-equipped
vehicles first used from August 1992. If the
CO level cannot be reduced far enough to
pass the test (and the fuel and ignition
systems are otherwise in good condition) then
the carburettor is badly worn, or there is some
problem in the fuel injection system or
catalytic converter (as applicable).
HC emissionsMWith the CO emissions within limits, HC
emissions must be no more than 1200 ppm
(parts per million). If the vehicle fails this test
at idle, it can be re-tested at around 2000 rpm;
if the HC level is then 1200 ppm or less, this
counts as a pass.
MExcessive HC emissions can be caused by
oil being burnt, but they are more likely to be
due to unburnt fuel.
Diesel models
MThe only emission test applicable to Diesel
engines is the measuring of exhaust smoke
density. The test involves accelerating the
engine several times to its maximum
unloaded speed.
Note: It is of the utmost importance that the
engine timing belt is in good condition before
the test is carried out.
M
Excessive smoke can be caused by a dirty
air cleaner element. Otherwise, professional
advice may be needed to find the cause.
4Checks carried out on
YOUR VEHICLE’S EXHAUST
EMISSION SYSTEM