1989 FORD FIESTA jump cable

Ignition timing
1.4 and 1.6 litre carburettor models with distributor:For use with 4-star leaded petrol (97 RON) . . . . . . . . . . . . . . . . . . . . 12°BTDC at idle speed (vacuum pipe disconnected and plugged)
For use with unleaded petrol (95 or 98 RON) . . . . . . . . . . . . . . . . . . . 8° BTDC at idle speed (vacuum pipe disconnected and plugged)
1.4 litre CFi fuel injection models with distributor (pre-Sept 1990) . . . . 10°BTDC at idle speed (set using STAR test equipment - refer to text)
All other models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .\
. . . . . . . Totally controlled by ignition module or EEC IV engine management module
Spark plugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .\
. . . . . . . See Chapter 1 Specifications
Torque wrench settingsNmlbf ft
Crankshaft position sensor (all engines except Zetec) . . . . . . . . . . . . . . 3 to 4 2 to 3
Crankshaft position sensor to bracket (Zetec engines) . . . . . . . . . . . . . 7 to 9 5 to 7
Crankshaft position sensor bracket to engine (Zetec engines) . . . . . . . 18 to 23 13 to 17
DIS/E-DIS ignition coil to bracket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 to 7 4 to 5
DIS/E-DIS ignition coil bracket to engine (all engines except Zetec) . . . 9 to 12 7 to 9
DIS/E-DIS ignition coil bracket to engine (Zetec engines) . . . . . . . . . . . 18 to 23 13 to 17
5B•2 Ignition system
1595Ford Fiesta Remake
1 General information and
precautions
General information
The ignition system is responsible for
igniting the air/fuel mixture in each cylinder, at
the correct moment in relation to engine
speed and load, as the electrical spark
generated jumps the spark plug gap. The ignition system is based on feeding low
tension (LT) voltage from the battery to the
ignition coil where it is converted to high
tension (HT) voltage. The high tension voltage
is powerful enough to jump the spark plug
gap in the cylinders many times a second
under high compression pressures, providing
that the system is in good condition. A number of different ignition systems have
been fitted to Fiesta models depending on the
year of manufacture, type of fuel system fitted
and the emission level that the vehicle has
been designed to meet. Broadly speaking the
systems can be sub-divided into two
categories - distributor ignition systems and
distributorless ignition systems. One version of the distributor ignition
system is fitted to all CVH engines with
carburettors. A second (more sophisticated)
version is fitted to pre-September 1990 CVH
engines with CFi fuel injection. Distributorless ignition systems are fitted to
all HCS, PTE and Zetec engines, and to all
CVH engines with fuel injection except pre-
September 1990 CFi versions.
Distributor ignition systems (CVH
engines with carburettor)
The ignition system is divided into two
circuits; low tension (primary) and high
tension (secondary). The low tension circuit
consists of the battery, ignition switch, coil
primary windings, ignition amplifier module
and the signal generating system inside the distributor. The signal generating system
comprises the trigger coil, trigger wheel,
stator, permanent magnet and trigger coil to
ignition amplifier module connector. The high
tension circuit consists of the coil secondary
windings, the HT lead from the coil to the
distributor cap, the distributor cap, the rotor
arm, the HT leads from the distributor cap to
the spark plugs and the spark plugs
themselves.
When the system is in operation, low
tension voltage is changed in the coil into high
tension voltage by the action of the electronic
amplifier module in conjunction with the signal
generating system. Any change in the
magnetic field force (flux), created by the
movement of the trigger wheel relative to the
magnet, induces a voltage in the trigger coil.
This voltage is passed to the ignition amplifier
module which switches off the ignition coil
primary circuit. This results in the collapse of
the magnetic field in the coil which
generates the high tension voltage. The high
tension voltage is then fed, via the coil HT
lead and the carbon brush in the centre of the
distributor cap, to the rotor arm. The voltage
passes across to the appropriate metal
segment in the cap and via the spark plug HT
lead to the spark plug where it finally jumps
the spark plug gap to earth. The distributor is driven by an offset drive
dog locating to a correspondingly offset slot
in the end of the camshaft.
The ignition advance is a function of the
distributor and is controlled both mechanically
and by a vacuum operated system. The
mechanical governor mechanism consists of
two weights which move out from the
distributor shaft as the engine speed rises due
to centrifugal force. As they move outwards,
they rotate the trigger wheel relative to the
distributor shaft and so advance the spark.
The weights are held in position by two light
springs and it is the tension of the springs
which is largely responsible for correct spark
advancement. The vacuum control consists of a
diaphragm, one side of which is connected
via a small bore hose to the carburettor or
throttle housing, and the other side to the
distributor. Depression in the inlet manifold
and/or carburettor, which varies with engine
speed and throttle position, causes the
diaphragm to move, so moving the stator and
advancing or retarding the spark. A fine
degree of control is achieved by a spring in
the diaphragm assembly. Additionally, one or more vacuum valve
may be incorporated in the vacuum line
between the inlet manifold or carburettor and
the distributor. The function of these is to
control the vacuum felt at the distributor and
to prevent fuel entering along the vacuum line
(as applicable).
Distributor ignition systems (pre-
September 1990 CVH engines with
CFi fuel injection)
The ignition system is divided into two
circuits; low tension (primary) and high
tension (secondary). The low tension circuit
consists of the battery, ignition switch, ignition
module, ballast resistor, coil primary windings
and “Hall effect” distributor. The high tension
circuit consists of the coil secondary
windings, coil-to-distributor cap HT lead,
distributor cap, rotor arm, spark plug HT leads
and spark plugs. The system is under the
overall control of the EEC IV engine
management module which also controls the
fuel injection and emission control equipment. When the system is in operation the
distributor supplies the EEC IV module with a
crankshaft position reference signal to enable
an initial ignition timing setting to be
established. This signal is generated by
means of a trigger vane attached to the
distributor shaft and which rotates in the gap
between a permanent magnet and a sensor.
The trigger vane has four cut-outs, one for
each cylinder. When one of the trigger vane
cut-outs is in line with the sensor, magnetic
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flux can pass between the magnet and the
sensor. When a trigger vane segment is in line
with the sensor, the magnetic flux is diverted
through the trigger vane, away from the
sensor. The sensor detects the change in
magnetic flux and sends an impulse to the
EEC IV module. Additional data is received
from the engine coolant temperature sensor,
manifold absolute pressure sensor, inlet air
temperature sensor, throttle position sensor
and vehicle speed sensor. Using this
information the EEC IV module calculates the
optimum ignition advance setting and
switches off the low tension circuit via the
ignition module. This results in the collapse of
the magnetic field in the coil which generates
the high tension voltage. The high tension
voltage is then fed, via the coil HT lead and
the carbon brush in the centre of the
distributor cap, to the rotor arm. The voltage
passes across to the appropriate metal
segment in the cap and via the spark plug HT
lead to the spark plug where it finally jumps
the spark plug gap to earth. It can be seen
that the ignition module functions basically as
a high current switch by controlling the low
tension supply to the ignition coil primary
windings.In the event of failure of a sensor, the
EEC IV module will substitute a preset value
for that input to allow the system to continue
to function. In the event of failure of the
EEC IV module, a “limited operation strategy”
(LOS) function allows the vehicle to be driven,
albeit at reduced power and efficiency. The
EEC IV module also has a “keep alive
memory” (KAM) function which stores idle and
drive values and codes which can be used to
indicate any system fault which may occur.
Distributorless ignition systems
The main ignition system components
include the ignition switch, the battery, the
crankshaft speed/position sensor, the ignition
module, the coil, the primary (low tension/LT)
and secondary (high tension/HT) wiring
circuits, and the spark plugs. The system used on carburettor models is
termed DIS (Distributorless Ignition System),
and on fuel injection models E-DIS, (Electronic
Distributorless Ignition System). The primary
difference between the two is that the DIS
system is an independent ignition control
system while the E-DIS system operates in
conjunction with the EEC IV engine
management module which also controls the
fuel injection and emission control systems.
With both systems, the main functions of
the distributor are replaced by a computerised
ignition module and a coil unit. The coil unit
combines a double-ended pair of coils - each
time a coil receives an ignition signal, two
sparks are produced, at each end of the
secondary windings. One spark goes to a
cylinder on compression stroke and the other
goes to the corresponding cylinder on its
exhaust stroke. The first will give the correct power stroke, but the second spark will have
no effect (a “wasted spark”), occurring as it
does during exhaust conditions.
The ignition signal is generated by a
crankshaft position sensor which scans a
series of 36 protrusions on the periphery of
the engine flywheel. The inductive head of the
crankshaft position sensor runs just above the
flywheel periphery and as the crankshaft
rotates, the sensor transmits a pulse to the
ignition module every time a protrusion
passes it. There is one missing protrusion in
the flywheel periphery at a point
corresponding to 90° BTDC. The ignition
module recognises the absence of a pulse
from the crankshaft position sensor at this
point to establish a reference mark for
crankshaft position. Similarly, the time interval
between absent pulses is used to determine
engine speed. On carburettor engines, the ignition module
receives signals provided by information
sensors which monitor various engine
functions (such as crankshaft position,
coolant temperature, inlet air temperature,
inlet manifold vacuum etc). This information
allows the ignition module to generate the
optimum ignition timing setting under all
operating conditions.
On fuel injection engines, the ignition
module operates in conjunction with the
EEC IV engine management module, and
together with the various additional
information sensors and emission control
components, provides total control of the fuel
and ignition systems to form a complete
engine management package. The information contained in this Chapter
concentrates on the ignition-related
components of the engine management
system. Information covering the fuel, exhaust
and emission control components can be
found in the applicable Parts of Chapter 4.
Precautions
When working on the ignition system, take
the following precautions:
a) Do not keep the ignition switch on for
more than 10 seconds if the engine will
not start.
b) If a separate tachometer is ever required
for servicing work, consult a dealer
service department before buying a
tachometer for use with this vehicle -
some tachometers may be incompatible
with these types of ignition systems - and
always connect it in accordance with the
equipment manufacturer’s instructions.
c) Never connect the ignition coil terminals to earth. This could result in damage to
the coil and/or the ignition module.
d) Do not disconnect the battery when the
engine is running.
e) Make sure that the ignition module is
properly earthed.
f) Refer to the warning at the beginning of the next Section concerning HT voltage.
2 Ignition system - testing
2
Warning: Voltages produced by
an electronic ignition system are
considerably higher than those
produced by conventional
ignition systems. Extreme care must be
taken when working on the system with
the ignition switched on. Persons with
surgically-implanted cardiac pacemaker
devices should keep well clear of the
ignition circuits, components and test
equipment.
Note: Refer to the precautions given in
Section 1 of Part A of this Chapter before
starting work. Always switch off the ignition
before disconnecting or connecting any
component and when using a multi-meter to
check resistances.
1 If the engine turns over but won’t start,
disconnect the (HT) lead from any spark plug,
and attach it to a calibrated tester (available at
most automotive accessory shops). Connect
the clip on the tester to a good earth - a bolt
or metal bracket on the engine. If you’re
unable to obtain a calibrated ignition tester,
have the check carried out by a Ford dealer
service department or similar. Any other form
of testing (such as jumping a spark from the
end of an HT lead to earth) is not
recommended, because of the risk of
personal injury, or of damage to the ignition
module.
2 Crank the engine, and watch the end of the
tester to see if bright blue, well-defined sparks
occur.
3 If sparks occur, sufficient voltage is
reaching the plug to fire it. Repeat the
check at the remaining plugs, to ensure
that all leads are sound and that the
coil is serviceable. However, the plugs
themselves may be fouled or faulty, so
remove and check them as described in
Chapter 1.
4 If no sparks or intermittent sparks occur,
the spark plug lead(s) may be defective. Also,
on distributor systems, there may be
problems with the rotor arm or distributor cap
- check all these components as described in
Chapter 1.
5 If there’s still no spark, check the coil’s
electrical connector (where applicable), to
make sure it’s clean and tight. Check for full
battery voltage to the coil at the connector’s
centre terminal. Check the coil itself (see
Section 3). Make any necessary repairs, then
repeat the check again.
6 The remainder of the system checks should
be left to a dealer service department
or other qualified repair facility, as there is a
chance that the ignition module may
be damaged if tests are not performed
properly.
Ignition system 5B•3
5B
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wiring diagrams are included at the end of this
manual.
2Before attempting to diagnose an electrical
fault, first study the appropriate wiring
diagram, to obtain a complete understanding
of the components included in the particular
circuit concerned. The possible sources of a
fault can be narrowed down by noting if other
components related to the circuit are
operating properly. If several components or
circuits fail at one time, the problem is likely to
be related to a shared fuse or earth
connection.
3 Electrical problems usually stem from
simple causes, such as loose or corroded
connections, a faulty earth connection, a
blown fuse, a melted fusible link, or a faulty
relay (refer to Section 3 for details of testing
relays). Visually inspect the condition of all
fuses, wires and connections in a problem
circuit before testing the components. Use
the wiring diagrams to 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 test leads can also
be used for certain tests); an ohmmeter (to
measure resistance and check for continuity);
a battery and set of test leads; and a jumper
wire, preferably with a circuit breaker or fuse
incorporated, which can be used to bypass
suspect wires or electrical components.
Before attempting to locate a problem with
test instruments, use the wiring diagram to
determine where to make the connections.
Warning: Under no
circumstances may live
measuring instruments such as
ohmmeters, voltmeters or a bulb
and test leads be used to test any of the
air bag circuitry or components. Any
testing in these areas must be left to a
Ford dealer as there is a danger of
activating the system if the correct
procedures are not followed.
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 the 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 described 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.
8 Short-circuit faults are caused by a “short”
somewhere in the circuit, which allows the 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 bodyshell. A
short-circuit fault will normally cause the
relevant circuit fuse to blow.
Finding an open-circuit
9
To check for an open-circuit, connect one
lead of a circuit tester or the negative lead of a
voltmeter either to the battery negative
terminal or to a known good earth.
10 Connect the other lead to a connector in
the circuit being tested, preferably nearest to
the battery or fuse. At this point, battery
voltage should be present, unless the lead
from the battery or the fuse itself is faulty
(bearing in mind that some circuits are live
only when the ignition switch is moved to a
particular position).
11 Switch on the circuit, then connect the
tester lead to the connector nearest the circuit
switch on the component side.
12 If voltage is present (indicated either by
the tester bulb lighting or a voltmeter reading,
as applicable), this means that the section of
the circuit between the relevant connector
and the switch is problem-free.
13 Continue to check the remainder of 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 fuse from the circuit,
and connect a circuit tester or voltmeter to the
fuse connections.
17 Switch on the circuit, bearing 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 during this test,
but the fuse still blows with the load(s)
reconnected, 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 vehicle body -
and many systems are wired so that they only
receive a positive feed, the current returning
via the metal of the 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 of a
circuit, to a puzzling partial failure. In
particular, lights may shine dimly (especially
when another circuit sharing the same earth
point is in operation), motors (eg wiper
motors or the radiator cooling fan motor) may
run slowly, and the operation of one circuit
may have an apparently-unrelated effect on
another. Note that on many vehicles, earth
straps are used between certain
components, such as the engine/
transmission and the body, usually where
there is no metal-to-metal contact between
components, due to flexible rubber
mountings, etc.
21
To check whether a component is
properly earthed, disconnect the battery (refer
to Chapter 5A, Section 1) and connect one
lead of an ohmmeter to a known good earth
point. Connect the other lead to the wire or
earth connection being tested. The 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
both the bodyshell and the wire terminal (or
the component earth connection mating
surface) back to bare metal. Be careful to
remove all traces of dirt and corrosion, then
use a knife to trim away any paint, so that a
clean metal-to-metal joint is made. On
reassembly, tighten the joint fasteners
securely; if a wire terminal is being refitted,
use serrated washers between the terminal
and the bodyshell, to ensure a clean and
secure connection. When the connection is
remade, prevent the onset of corrosion in the
future by applying a coat of petroleum jelly or
silicone-based grease, or by spraying on (at
regular intervals) a proprietary ignition sealer
or a water-dispersant lubricant.
3 Fuses and relays -
general information
Note: It is important to note that the ignition
switch and the appropriate electrical circuit
must always be switched off before any of the
fuses (or relays) are removed and renewed.
1 The main fuse and relay board is located
below the facia panel to the right of the
steering wheel. The fuses can be inspected
and if necessary renewed, by removing the
hinged access cover. The remaining
additional fuses and relays (depending on
model) may be accessed by removing the two
fuse board retaining screws, releasing the
retaining lugs on either side of the main fuse
plate and withdrawing the fuse/relay board
downwards into the driver’s footwell. Each
fuse location is numbered - refer to the fuse
chart in the Specifications at the start of this
Chapter to check which circuits are protected
by each fuse. Plastic tweezers are attached to
12•4 Body electrical systems
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1595 Ford Fiesta Remake
Fault findingREF•17
REF
Fuel and exhaust systems
Excessive fuel consumption
m
mUnsympathetic driving style, or adverse conditions.
m
m Air filter element dirty or clogged (Chapter 1).
m
m Engine management system fault (Chapters 1, 4A, 4B, 4C, 4D, 4E
or 5B).
m m Tyres under-inflated ( “Weekly Checks”).
Fuel leakage and/or fuel odour
m
mDamaged or corroded fuel tank, pipes or connections (Chapter 1).
m
m Charcoal canister and/or connecting pipes leaking (Chapters 1
and 4E).
Excessive noise or fumes from exhaust system
m mLeaking exhaust system or manifold joints (Chapters 1 or 4E).
m
m Leaking, corroded or damaged silencers or pipe (Chapters 1 or 4E).
m
m Broken mountings, causing body or suspension contact (Chap-
ters 1 or 4E).
Clutch
Pedal travels to floor - no pressure or very little
resistance
m mBroken clutch cable (Chapter 6).
m
m Faulty clutch automatic adjuster (Chapter 6).
m
m Broken clutch release bearing or fork (Chapter 6).
m
m Broken diaphragm spring in clutch pressure plate (Chapter 6).
Clutch fails to disengage (unable to select gears)
m
mFaulty clutch automatic adjuster (Chapter 6).
m
m Clutch disc sticking on transmission input shaft splines (Chapter 6).
m
m Clutch disc sticking to flywheel or pressure plate (Chapter 6).
m
m Faulty pressure plate assembly (Chapter 6).
m
m Clutch release mechanism worn or incorrectly assembled (Chapter 6).
Clutch slips (engine speed increases, with no
increase in vehicle speed)
m mFaulty clutch automatic adjuster (Chapter 6).
m
m Clutch disc linings excessively worn (Chapter 6).
m
m Clutch disc linings contaminated with oil or grease (Chapter 6).
m
m Faulty pressure plate or weak diaphragm spring (Chapter 6).
Judder as clutch is engaged
m
mClutch disc linings contaminated with oil or grease (Chapter 6).
m
m Clutch disc linings excessively worn (Chapter 6).
m
m Clutch cable sticking or frayed (Chapter 6).
m
m Faulty or distorted pressure plate or diaphragm spring (Chapter 6).
m
m Worn or loose engine/transmission mountings (Chapters 2A, 2B
or 2C).
m m Clutch disc hub or transmission input shaft splines worn (Chap-
ter 6).
Noise when depressing or releasing clutch pedal
m mWorn clutch release bearing (Chapter 6).
m
m Worn or dry clutch pedal bushes (Chapter 6).
m
m Faulty pressure plate assembly (Chapter 6).
m
m Pressure plate diaphragm spring broken (Chapter 6).
m
m Broken clutch disc cushioning springs (Chapter 6).
Manual transmission
Noisy in neutral with engine running
m
mInput shaft bearings worn (noise apparent with clutch pedal
released, but not when depressed) (Chapter 7A).*
m m Clutch release bearing worn (noise apparent with clutch pedal
depressed, possibly less when released) (Chapter 6).
Noisy in one particular gear
m mWorn, damaged or chipped gear teeth (Chapter 7A).*
Difficulty engaging gears
m
mClutch fault (Chapter 6).
m
m Worn or damaged gear linkage (Chapter 7A).
m
m Incorrectly-adjusted gear linkage (Chapter 7A).
m
m Worn synchroniser assemblies (Chapter 7A).*
Vibration
m
mLack of oil (Chapter 1).
m
m Worn bearings (Chapter 7A).*
Jumps out of gear
m
mWorn or damaged gear linkage (Chapter 7A).
m
m Incorrectly-adjusted gear linkage (Chapter 7A).
m
m Worn synchroniser assemblies (Chapter 7A).*
m
m Worn selector forks (Chapter 7A).*
Lubricant leaks
m
mLeaking differential side gear oil seal (Chapter 7A).
m
m Leaking housing joint (Chapter 7A).*
m
m Leaking input shaft oil seal (Chapter 7A).*
m
m Leaking selector shaft oil seal (Chapter 7A).
m
m Leaking speedometer drive pinion O-ring (Chapter 7A).
* Although the corrective action necessary to remedy the symptoms
described is beyond the scope of the home mechanic, the above
information should be helpful in isolating the cause of the condition,
so that the owner can communicate clearly with a professional
mechanic.
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1595 Ford Fiesta Remake
REF•24Glossary of technical terms
EEGR valveA valve used to introduce exhaust
gases into the intake air stream.
Electr onic control unit (ECU) A computer
which controls (for instance) ignition and fuel
injection systems, or an anti-lock braking
system. For more information refer to the
Haynes Automotive Electrical and Electronic
Systems Manual.
Electr onic Fuel Injection (EFI) A computer
contr olled fuel system that distributes fuel
thr ough an injector located in each intake port
of the engine.
Emergency brake A braking system,
independent of the main hydraulic system,
that can be used to slow or stop the vehicle if
the primary brakes fail, or to hold the vehicle
stationary even though the brake pedal isn’t
depr essed. It usually consists of a hand lever
that actuates either front or rear brakes
mechanically through a series of cables and
linkages. Also known as a handbrake or
parking brake.
Endfloat The amount of lengthwise
movement between two parts. As applied to a
crankshaft, the distance that the crankshaft
can move forward and back in the cylinder
block.
Engine management system (EMS) A
computer controlled system which manages
the fuel injection and the ignition systems in
an integrated fashion.
Exhaust manifold A part with several
passages through which exhaust gases leave
the engine combustion chambers and enter
the exhaust pipe.
FFan clutch A viscous (fluid) drive coupling
device which permits variable engine fan
speeds in relation to engine speeds. Feeler blade
A thin strip or blade of hardened
steel, ground to an exact thickness, used to
check or measure clearances between parts.
Firing order The order in which the engine
cylinders fire, or deliver their power strokes,
beginning with the number one cylinder.
Flywheel A heavy spinning wheel in which
ener gy is absorbed and stored by means of
momentum. On cars, the flywheel is attached
to the crankshaft to smooth out firing
impulses.
Fr ee play The amount of travel before any
action takes place. The “looseness” in a
linkage, or an assembly of parts, between the
initial application of force and actual
movement. For example, the distance the
brake pedal moves before the pistons in the
master cylinder are actuated.
Fuse An electrical device which protects a
cir cuit against accidental overload. The typical
fuse contains a soft piece of metal which is
calibrated to melt at a predetermined current
flow (expressed as amps) and break the
circuit.
Fusible link A circuit protection device
consisting of a conductor surrounded by
heat-r esistant insulation. The conductor is
smaller than the wire it protects, so it acts as
the weakest link in the circuit. Unlike a blown
fuse, a failed fusible link must frequently be
cut from the wire for replacement.
GGap The distance the spark must travel in
jumping from the centre electrode to the side electr
ode in a spark plug. Also refers to the
spacing between the points in a contact
br eaker assembly in a conventional points-
type ignition, or to the distance between the
r eluctor or rotor and the pickup coil in an
electr onic ignition.
Gasket Any thin, soft material - usually cork,
cardboar d, asbestos or soft metal - installed
between two metal surfaces to ensure a good
seal. For instance, the cylinder head gasket
seals the joint between the block and the
cylinder head.
Gauge An instrument panel display used to
monitor engine conditions. A gauge with a
movable pointer on a dial or a fixed scale is an
analogue gauge. A gauge with a numerical
r eadout is called a digital gauge.
HHalfshaft A rotating shaft that transmits
power from the final drive unit to a drive
wheel, usually when referring to a live rear axle.
Harmonic balancer A device designed to
r educe torsion or twisting vibration in the
crankshaft. May be incorporated in the
crankshaft pulley. Also known as a vibration
damper.
Hone An abrasive tool for correcting small
irr egularities or differences in diameter in an
engine cylinder, brake cylinder, etc.
Hydraulic tappet A tappet that utilises
hydraulic pressure from the engine’s
lubrication system to maintain zero clearance
(constant contact with both camshaft and
valve stem). Automatically adjusts to variation
in valve stem length. Hydraulic tappets also
r educe valve noise.
IIgnition timing The moment at which the
spark plug fires, usually expressed in the number of crankshaft degrees before the
piston reaches the top of its stroke.
Inlet manifold A tube or housing with
passages through which flows the air-fuel mixtur e (carburettor vehicles and vehicles with
thr ottle body injection) or air only (port fuel-
injected vehicles) to the port openings in the
cylinder head.
Exhaust manifold
Feeler blade
Adjusting spark plug gap
Gasket
EGR valve
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