Ford Orion. Manual — part 43

1

General information

To minimise pollution of the atmosphere

from incompletely-burned and evaporating
gases, and to maintain good driveability and
fuel economy, a number of emissions control
systems are used on these vehicles. They
include the following:
a)

The engine management system
(comprising both fuel and ignition

sub-

systems) itself.

b)

Positive Crankcase Ventilation (PCV)
system.

c)

Evaporative Emissions Control (EVAP)
system.

d)

Pulse-air system.

e)

Catalytic converter.

The Sections of this Chapter include

general descriptions, checking procedures
within the scope of the home mechanic, and
component renewal procedures (when
possible) for each of the systems listed above.

Before assuming an emissions control

system is malfunctioning, check the fuel and
ignition systems carefully (see Chapters 4 and
5). The diagnosis of some emissions control
devices requires specialised tools, equipment
and training. If checking and servicing
become too difficult, or if a procedure is
beyond the scope of your skills, consult your
dealer service department or other specialist.

This doesn’t mean, however, that emissions

control systems are particularly difficult to
maintain and repair. You can quickly and
easily perform many checks, and do most of

the regular maintenance, at home with
common tune-up and hand tools. Note: The
most frequent cause of emissions problems is
simply a loose or broken electrical connector
or vacuum hose, so always check the
electrical connectors and vacuum hoses first.

Pay close attention to any special

precautions outlined in this Chapter. It should
be noted that the illustrations of the various
systems may not exactly match the system
installed on your vehicle, due to changes
made by the manufacturer during production
or from year-to-year.

Vehicles sold in some areas will carry a

Vehicle Emissions Control Information (VECI)
label, and a vacuum hose diagram located in
the engine compartment. These contain
important specifications and setting
procedures for the various emissions control
systems, with the vacuum hose diagram
identifying emissions control components.
When servicing the engine or emissions
systems, the VECI label in your particular
vehicle should always be checked for the
latest information for your vehicle.

2

Electronic control systems -
description and precautions

Description

The sophistication of the emissions control

systems fitted, and hence their method of
electronic control, is dependant on the
emissions level that the engine has been
designed to meet. The engines covered in this

manual are all designed to meet one of the
three current emissions levels, namely, 15.04,
NEEC 5th, and US ‘83. The European 15.04 is
the least stringent of the three, and its
requirements are met by carburettor engines
having engine management systems
controlling the ignition-related components
only. Some of the additional emissions
systems described in this Chapter may also
be fitted. The US ‘83 regulations are the most
stringent. To meet these, an engine will need
a full engine management system, electronic
fuel injection (to allow precise control of the
air/fuel mixture ratio) a regulated catalytic
converter, and one or more of the additional
emissions systems described in this Chapter.

On carburettor engines, the exhaust

emissions requirements are met mainly by
precise control of the ignition timing, by
means of an ignition module receiving inputs
from sensors monitoring various engine
parameters, and additionally by the use of a
pulse-air system and unregulated catalytic
converter (see illustrations). The ignition
module fitted varies according to engine type,
but all operate in a similar fashion. Further
information on ignition module types and their
functions will be found in Chapter 5.

On fuel-injected engines, a highly-

sophisticated engine management system is
fitted, controlled by the EEC-IV microcomputer
in conjunction with an ignition module.

The EEC-IV (Electronic Engine Control,

fourth-generation) engine management
system controls fuel injection by means of a
microcomputer or ECU (Electronic Control
Unit) (see illustrations).

The ECU receives signals from various

sensors, which monitor changing engine

6•2 Emissions control systems

2.2A Diagram of engine monitoring sensors and actuators used on 1.3 litre carburettor engine models

Emissions control systems 6•3

2.2B Diagram of engine monitoring sensors and actuators used

on 1.4 and 1.6 litre carburettor engine models

2.4A Diagram of engine monitoring sensors and actuators used on

1.6 litre EFi fuel injected engine models to US ‘83 emission standard

6

2.4B Layout of engine management

system components and sensors

on Zetec engine models

A Fuel injector (1 of 4)
B Idle speed control valve
C Ignition coil and HT leads
D Charcoal canister-purge solenoid

valve

E Throttle position sensor
F Inlet air temperature sensor
G Camshaft position sensor
H Vehicle speed sensor
J Coolant temperature sensor
K E-DIS ignition module/electronic

vacuum regulator

L Oxygen sensor
M Crankshaft position sensor
N Air mass meter

operating conditions such as inlet air mass (ie,
inlet air volume and temperature), coolant
temperature, engine speed, acceleration/
deceleration, exhaust oxygen content, etc.
These signals are used by the ECU to
determine the correct injection duration.

The system is analogous to the central

nervous system in the human body - the
sensors (nerve endings) constantly relay
signals to the ECU (brain), which processes
the data and, if necessary, sends out a
command to change the operating
parameters of the engine (body) by means of
the actuators (muscles).

Here’s a specific example of how one

portion of this system operates. An oxygen
sensor, located in the exhaust downpipe,
constantly monitors the oxygen content of the
exhaust gas. If the percentage of oxygen in
the exhaust gas is incorrect, an electrical
signal is sent to the ECU. The ECU processes
this information, and then sends a command
to the fuel injection system, telling it to change
the air/fuel mixture; the end result is an air/fuel
mixture ratio which is constantly maintained
at a predetermined ratio, regardless of driving
conditions. This happens in a fraction of a
second, and goes on almost all the time while
the engine is running - the exceptions are that
the ECU cuts out the system and runs the
engine on values pre-programmed
(“mapped”) into its memory both while the
oxygen sensor is reaching its normal
operating temperature after the engine has
been started from cold, and when the throttle
is fully open for full acceleration.

In the event of a sensor malfunction, a back-

up circuit will take over, to provide driveability
until the problem is identified and fixed.

Precautions

a)

Always disconnect the battery terminals -
see Section 1 of Chapter 5 - before
removing any of the electronic control
system’s electrical connectors.

b)

When reconnecting the battery, be
particularly careful to avoid reversing the
positive and negative battery leads.

c)

Do not subject any components of the
system (especially the ECU) to severe
impact during removal or installation.

d)

Take care when carrying out fault
diagnosis. Even slight terminal contact
can invalidate a testing procedure, and
may damage one of the numerous
transistor circuits.

e)

Never attempt to work on the ECU - don’t
test it (with any kind of test equipment), or
open its cover.

f)

If you are inspecting electronic control
system components during rainy weather,
make sure that water does not enter any
part. When washing the engine
compartment, do not spray these parts or
their electrical connectors with water -
strong plastic bags should be wrapped
around these components to prevent
water ingress.

3

Self-diagnosis system -
general information

General

On fuel-injected engines with full engine

management systems, the various
components of the fuel, ignition and
emissions control systems (not forgetting the
same ECU’s control of sub-systems such as
the air conditioning and automatic
transmission, where appropriate) are so
closely interlinked that diagnosis of a fault in
any one component is virtually impossible
using traditional methods. Working on simpler
systems in the past, the experienced
mechanic may well have been able to use
personal skill and knowledge immediately to
pinpoint the cause of a fault, or quickly to
isolate the fault, by elimination; however, with
an engine management system integrated to
this degree, this is not likely to be possible in
most instances, because of the number of
symptoms that could arise from even a minor
fault.

So that the causes of faults can be quickly

and accurately traced and rectified, the ECU
is provided with a built-in self-diagnosis
facility, which detects malfunctions in the
system’s components. When a fault occurs,
three things happen: the ECU identifies the
fault, stores a corresponding code in its
memory, and (in most cases) runs the system
using back-up values pre-programmed
(“mapped”) into its memory; some form of
driveability is thus maintained, to enable the
vehicle to be driven to a garage for attention.

Any faults that may have occurred are

indicated in the form of two- or three-digit
codes when the system is connected (via the
built-in diagnosis or self-test connectors, as
appropriate) to special diagnostic equipment -
this points the user in the direction of the
faulty circuit, so that further tests can pinpoint
the exact location of the fault. Obviously, to
be able to interpret these fault codes
accurately requires special diagnostic test
equipment and an understanding of its use,
which puts this phase of the diagnostic
procedure outside the scope of the DIY
enthusiast. There are, however, a number of
checks that can be performed without
sophisticated equipment, and in many cases
these alone will find the cause of the trouble.

Given below is a procedure that should be

followed to trace an engine management
system fault from scratch. Most of the
operations described apply equally to
carburettor models with minimal emissions
control, right through to fuel-injected models
with full engine management. Read through
the procedure and decide how much you can
attempt, depending on your skill and
experience and the equipment available to
you, or whether it would be simpler to have
the vehicle attended to by your local Ford

dealer. If you are concerned about the
apparent complexity of the system, however,
remember that the following system checks
require nothing but care, patience and a few
minor items of equipment, and may well
eliminate the majority of faults.

Initial system checks

Note: When carrying out these checks to

trace a fault, remember that if the fault has
appeared only a short time after any part of
the vehicle has been serviced or overhauled,
the first place to check is where that work was
carried out, however unrelated it may appear,
to ensure that no carelessly-refitted
components are causing the problem.

If you are tracing the cause of a “partial”

engine fault, such as lack of performance, in
addition to the checks outlined below, check
the compression pressures (see Parts A, B or
C of Chapter 2, as applicable) and bear in
mind the possibility that one of the hydraulic
tappets (where applicable) might be faulty,
producing an incorrect valve clearance.
Check also that the fuel filter has been
renewed at the recommended intervals.

If the system appears completely dead,

remember the possibility that the
alarm/immobiliser system may be
responsible.
1 On fuel-injected models, the first check for
anyone without special test equipment is to
switch on the ignition, and to listen for the fuel
pump (the sound of an electric motor running,
audible from beneath the rear seats);
assuming there is sufficient fuel in the tank,
the pump should start and run for
approximately one or two seconds, then stop,
each time the ignition is switched on. If the
pump runs continuously all the time the
ignition is switched on, the electronic control
system is running in the back-up (or “limp-
home”) mode, referred to by Ford as “Limited
Operation Strategy” (LOS). This almost
certainly indicates a fault in the ECU itself, and
the vehicle should therefore be taken to a
Ford dealer for a full test of the complete
system using the correct diagnostic
equipment; do not waste time trying to test
the system without such facilities.
2 If the fuel pump is working correctly (or not
at all), a considerable amount of fault
diagnosis is still possible without special test
equipment. Start the checking procedure as
follows.
3 Open the bonnet and check the condition
of the battery connections - remake the
connections or renew the leads if a fault is
found (see Chapter 5, Section 1 before
disconnecting the battery). Use the same
techniques to ensure that all earth points in
the engine compartment provide good
electrical contact through clean, metal-to-
metal joints, and that all are securely fastened.
Many of these earth points will be on the inner
wings, and on most models, there is an earth
strap from the engine or transmission to the
vehicle body. Note that certain components

6•4 Emissions control systems

have their earth connection made directly
through the back of the component onto its
mounting surface, in which case, the
component should be removed, and the
mating surfaces cleaned. A smear of
petroleum jelly, or some water-dispersant
spray, will help to ensure a continued good
connection between the cleaned surfaces.
4 Referring to the information given in Chap-
ter 12 and in the wiring diagrams at the back of
this manual, check that all fuses protecting the
circuits related to the engine management
system are in good condition. Fit new fuses if
required; while you are there, check that all
relays are securely plugged into their sockets.
5 Next work methodically around the engine
compartment, checking all visible wiring, and
the connections between sections of the
wiring loom. What you are looking for at this
stage is wiring that is obviously damaged by
chafing against sharp edges, or against
moving suspension/transmission components
and/or the auxiliary drivebelt, by being
trapped or crushed between carelessly-
refitted components, or melted by being
forced into contact with hot engine castings,
coolant pipes, etc. In almost all cases,
damage of this sort is caused in the first
instance by incorrect routing on reassembly
after previous work has been carried out (see
the note at the beginning of this sub-Section).
6 Obviously wires can break or short together
inside the insulation so that no visible evidence
betrays the fault, but this usually only occurs
where the wiring loom has been incorrectly
routed so that it is stretched taut or kinked
sharply; either of these conditions should be
obvious on even a casual inspection. If this is
thought to have happened and the fault proves
elusive, the suspect section of wiring should be
checked very carefully during the more detailed
checks which follow.
7 Depending on the extent of the problem,
damaged wiring may be repaired by rejoining
the break or splicing-in a new length of wire,
using solder to ensure a good connection,
and remaking the insulation with adhesive
insulating tape or heat-shrink tubing, as
desired. If the damage is extensive, given the
implications for the vehicle’s future reliability,
the best long-term answer may well be to
renew that entire section of the loom, however
expensive this may appear.
8 When the actual damage has been
repaired, ensure that the wiring loom is re-
routed correctly, so that it is clear of other
components, is not stretched or kinked, and is
secured out of harm’s way using the plastic
clips, guides and ties provided.
9 Check all electrical connectors, ensuring
that they are clean, securely fastened, and
that each is locked by its plastic tabs or wire
clip, as appropriate. If any connector shows
external signs of corrosion (accumulations of
white or green deposits, or streaks of “rust”),
or if any is thought to be dirty, it must be
unplugged and cleaned using electrical
contact cleaner. If the connector pins are

severely corroded, the connector must be
renewed; note that this may mean the renewal
of that entire section of the loom - see your
local Ford dealer for details.
10 If the cleaner completely removes the
corrosion to leave the connector in a
satisfactory condition, it would be wise to
pack the connector with a suitable material
which will exclude dirt and moisture, and
prevent the corrosion from occurring again; a
Ford dealer may be able to recommend a
suitable product. Note: The system’s
connectors use gold-plated pins, which must
not be mixed with the older tin-plated types
(readily identifiable from the different colour) if
a component is renewed, nor must the lithium
grease previously used to protect tin-plated
pins be used on gold-plated connectors.
11 Following the accompanying schematic
diagrams, and working methodically around
the engine compartment, check carefully that
all vacuum hoses and pipes are securely
fastened and correctly routed, with no signs
of cracks, splits or deterioration to cause air
leaks, or of hoses that are trapped, kinked, or
bent sharply enough to restrict air flow. Check
with particular care at all connections and
sharp bends, and renew any damaged or
deformed lengths of hose.
12 Working from the fuel tank, via the filter, to
the carburettor or fuel rail (and including the
feed and return), check the fuel lines, and
renew any that are found to be leaking,
trapped or kinked.
13 Check that the accelerator cable is
correctly secured and adjusted; renew the
cable if there is any doubt about its condition,
or if it appears to be stiff or jerky in operation.
Refer to the relevant Sections of Chapter 4 for
further information, if required.
14 Unclip the air cleaner cover, and check
that the air filter element and the crankcase
ventilation system filter (where applicable) are
not clogged or soaked. (A clogged air filter will
obstruct the inlet air flow, causing a
noticeable effect on engine performance; a
clogged crankcase ventilation system filter
will inhibit crankcase “breathing”). Renew or
clean the filter(s) as appropriate; refer to the
relevant Sections of Chapter 1 for further
information, if required.
15 Start the engine and allow it to idle. Note:
Working in the engine compartment while the
engine is running requires great care if the risk
of personal injury is to be avoided; among the
dangers are burns from contact with hot
components, or contact with moving
components such as the radiator cooling fan
or the auxiliary drivebelt. Refer to “Safety
first!” at the front of this manual before
starting, and ensure that your hands, and long
hair or loose clothing, are kept well clear of
hot or moving components at all times.
16 Working from the air inlet, via the air
cleaner assembly and carburettor, or on fuel-
injected models, the air mass meter to the
throttle housing and inlet manifold (and
including the various vacuum hoses and pipes

connected to these), check for air leaks.
Usually, these will be revealed by sucking or
hissing noises, but minor leaks may be traced
by spraying a solution of soapy water on to
the suspect joint; if a leak exists, it will be
shown by the change in engine note and the
accompanying air bubbles (or sucking-in of
the liquid, depending on the pressure
difference at that point). If a leak is found at
any point, tighten the fastening clamp and/or
renew the faulty components, as applicable.
17 Similarly, work from the cylinder head, via
the manifold to the tailpipe, to check that the
exhaust system is free from leaks. The
simplest way of doing this, if the vehicle can
be raised and supported safely and with
complete security while the check is made, is
to temporarily block the tailpipe while listening
for the sound of escaping exhaust gases; any
leak should be evident. If a leak is found at
any point, tighten the fastening clamp bolts
and/or nuts, renew the gasket, and/or renew
the faulty section of the system, as necessary,
to seal the leak.
18 It is possible to make a further check of
the electrical connections by wiggling each
electrical connector of the system in turn as
the engine is idling; a faulty connector will be
immediately evident from the engine’s
response as contact is broken and remade. It
may be possible with some connectors to
carefully bend the connector pins to improve
the contact being made. However, a faulty
connector should really be renewed, to ensure
the future reliability of the system (note that
this may mean the renewal of that entire
section of the loom - see your local Ford
dealer for details).
19 Switch off the engine. If the fault is not yet
identified, the next step is to check the
ignition voltages, using an engine analyser
with an oscilloscope - without such
equipment, the only tests possible are to
remove and check each spark plug in turn, to
check the spark plug (HT) lead connections
and resistances, and to check the
connections and resistances of the ignition
coil. Refer to the relevant Sections of
Chapters 1 and 5.
20 The final step in these initial checks would
be to use an exhaust gas analyser to measure
the CO level at the exhaust tailpipe. This check
cannot be made without special test equipment
- see your local Ford dealer for details.

4

Information sensors - general
information, testing, removal
and refitting

5

Note: This Section is concerned principally
with the sensors which give the ECU the
information it needs to control the various
engine management sub-systems - for further
details of those systems and their other
components, refer to the relevant Chapter of
this manual. Not all of the sensors listed below
are fitted to all engines.

Emissions control systems 6•5

6