turn signal bulb FORD FIESTA 1989 Service Repair Manual

This is used to refine the calculations made by
the module, when determining the correct
amount of fuel required to achieve the ideal
air/fuel mixture ratio.A throttle position sensor is mounted on the
end of the throttle valve spindle, to provide
the EEC IV module with a constantly-varying
(analogue) voltage signal corresponding to the
throttle opening. This allows the module to
register the driver’s input when determining
the amount of fuel required by the engine. Road speed is monitored by the vehicle
speed sensor. This component is a Hall-effect
generator, mounted on the transmission’s
speedometer drive. It supplies the EEC IV
module with a series of pulses corresponding
to the vehicle’s road speed, enabling the
module to control features such as the fuel
shut-off on overrun. A manifold absolute pressure sensor
measures inlet manifold vacuum, and supplies
this information to the module for calculation
of engine load at any given throttle position. Where power steering is fitted, a pressure-
operated switch is screwed into the power
steering system’s high-pressure pipe. The
switch sends a signal to the EEC IV module to
reduce engine speed should the power
steering fluid pressure become excessively
high. Certain later engines may be fitted with a
heater in the inlet manifold. This is controlled
by the EEC IV module to ensure that, even
before the effect of the coolant heating
becomes apparent, the manifold is warmed-
up. This prevents fuel droplets condensing in
the manifold, thus improving driveability and
reducing exhaust emissions when the engine
is cold.
The oxygen sensor in the exhaust system
provides the EEC IV module with constant
feedback - “closed-loop” control - which
enables it to adjust the mixture to provide the
best possible conditions for the catalytic
converter to operate.
Precautions
Warning: Petrol is extremely
flammable - great care must be
taken when working on any part
of the fuel system. Do not
smoke or allow any naked flames or
uncovered light bulbs near the work area.
Note that gas powered domestic
appliances with pilot flames, such as
heaters, boilers and tumble dryers, also
present a fire hazard - bear this in mind if
you are working in an area where such
appliances are present. Always keep a
suitable fire extinguisher close to the work
area and familiarise yourself with its
operation before starting work. Wear eye
protection when working on fuel systems
and wash off any fuel spilt on bare skin
immediately with soap and water. Note
that fuel vapour is just as dangerous as
liquid fuel; a vessel that has just been
emptied of liquid fuel will still contain vapour and can be potentially explosive.
Petrol is a highly dangerous and volatile
liquid, and the precautions necessary
when handling it cannot be overstressed.
Many of the operations described in this
Chapter involve the disconnection of fuel
lines, which may cause an amount of fuel
spillage. Before commencing work, refer
to the above Warning and the information
in “Safety first” at the beginning of this
manual. When working with fuel system
components, pay particular attention to
cleanliness - dirt entering the fuel system
may cause blockages which will lead to
poor running.
Note: Residual pressure will remain in the fuel
lines long after the vehicle was last used,
when disconnecting any fuel line, it will be
necessary to depressurise the fuel system as
described in Section 2 .
2 Fuel system-
depressurisation
1
Note: Refer to the warning note in Section 1
before proceeding.
Warning: The following
procedure will merely relieve the
pressure in the fuel system -
remember that fuel will still be present in
the system components, and take
precautions accordingly before
disconnecting any of them.
1 The fuel system referred to in this Chapter
is defined as the fuel tank and tank-mounted
fuel pump/fuel gauge sender unit, the fuel
filter, the fuel injector, fuel pressure regulator,
and the metal pipes and flexible hoses of the
fuel lines between these components. All
these contain fuel, which will be under
pressure while the engine is running and/or
while the ignition is switched on.
2 The pressure will remain for some time after
the ignition has been switched off, and must
be relieved before any of these components is
disturbed for servicing work.
3 The simplest depressurisation method is to
disconnect the fuel pump electrical supply by
removing the fuel pump fuse (No 19) and
starting the engine; allow the engine to idle
until it dies through lack of fuel pressure. Turn
the engine over once or twice on the starter to
ensure that all pressure is released, then
switch off the ignition; do not forget to refit the
fuse when work is complete.
4 Note that, once the fuel system has been
depressurised and drained (even partially), it
will take significantly longer to restart the
engine - perhaps several seconds of cranking
- before the system is refilled and pressure
restored.
3 Fuel lines and fittings -
general information
Note: Refer to the warning note in Section 1
before proceeding.
Disconnecting and connecting
quick-release couplings
1 Quick-release couplings are employed at
many of the unions in the fuel feed and return
lines.
2 Before disconnecting any fuel system
component, relieve the residual pressure in
the system (see Section 2), and equalise tank
pressure by removing the fuel filler cap.
Warning: This procedure will
merely relieve the increased
pressure necessary for the
engine to run - remember that
fuel will still be present in the system
components, and take precautions
accordingly before disconnecting any of
them.
3 Release the protruding locking lugs on each
union, by squeezing them together and
carefully pulling the coupling apart. Use rag to
soak up any spilt fuel. Where the unions are
colour-coded, the pipes cannot be confused.
Where both unions are the same colour, note
carefully which pipe is connected to which,
and ensure that they are correctly
reconnected on refitting.
4 To reconnect one of these couplings, press
them together until the locking lugs snap into
their groove. Switch the ignition on and off
five times to pressurise the system, and check
for any sign of fuel leakage around the
disturbed coupling before attempting to start
the engine.
Checking
5 Checking procedures for the fuel lines are
included in Chapter 1.
Component renewal
6 If any damaged sections are to be renewed,
use original-equipment replacement hoses or
pipes, constructed from exactly the same
material as the section being replaced. Do not
install substitutes constructed from inferior or
inappropriate material; this could cause a fuel
leak or a fire.
7 Before detaching or disconnecting any part
of the fuel system, note the routing of all
hoses and pipes, and the orientation of all
clamps and clips. Replacement sections must
be installed in exactly the same manner.
8 Before disconnecting any part of the fuel
system, be sure to relieve the fuel system
pressure (see Section 2), and equalise tank
pressure by removing the fuel filler cap. Also
disconnect the battery negative (earth) lead -
see Chapter 5A, Section 1. Cover the fitting
being disconnected with a rag, to absorb any
fuel that may spray out.
Fuel system - central fuel injection engines 4B•3
4B
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