fuel filter FORD MONDEO 1993 Service Owner's Manual

(b) If the pressure is low, pinch the fuel return
line. If the pressure now goes up, renew
the fuel pressure regulator. If the pressure
does not increase, check the fuel feed
line, the fuel pump and the fuel filter.
6Detach the vacuum hose from the fuel
pressure regulator; the pressure shown on the
gauge should increase. Note the increase in
pressure, and compare it with that listed in
this Chapter’s Specifications. If the pressure
increase is not as specified, check the
vacuum hose and pressure regulator.
7Reconnect the regulator vacuum hose, and
switch off the engine. Verify that the fuel
pressure stays at the specified level for five
minutes after the engine is turned off.
8Carefully disconnect the fuel pressure
gauge. Be sure to cover the fitting with a rag
before slackening it. Mop up any spilt petrol.
9Run the engine, and check that there are no
fuel leaks.
Warning: Petrol is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. Don’t smoke,
or allow open flames or bare light bulbs,
near the work area. Don’t work in a garage
where a natural gas-type appliance (such
as a water heater or clothes dryer) with a
pilot light is present. If you spill any fuel on
your skin, rinse it off immediately with
soap and water. When you perform any
kind of work on the fuel system, wear
safety glasses, and have a Class B type
fire extinguisher on hand.
Note: Ford specify the use of their service tool
23-038 (a large box spanner with projecting teeth
to engage the fuel pump/sender unit retaining
ring’s slots) for this task. While alternatives are
possible, as shown below, in view of the difficulty
experienced in removing and refitting the
pump/sender unit, owners are strongly advised
to obtain this tool before starting work. The help
of an assistant will be required.
1Relieve the residual pressure in the fuel
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.
2Disconnect the battery negative (earth) lead
- see Chapter 5, Section 1.
3Unbolt or fold forwards (as appropriate) the
rear seat base cushion (see Chapter 11).
Withdraw from the vehicle’s floor the grommet
covering the fuel pump/sender unit. Wash off
any dirt from the tank’s top surface, and dry it;
use a vacuum cleaner to clean the immediate
surroundings of the vehicle’s interior, to
reduce the risk of introducing water, dirt and
dust into the tank while it is open.
4Unplug the fuel pump/sender unit’s
electrical connector (see illustration).
5To disconnect the fuel feed and return
pipes from the unit, release each pipe’s
coupling, by squeezing together the
protruding locking lugs on each union and
carefully pulling the coupling apart. Use rag to
soak up any spilt fuel. Where the couplings
are difficult to separate, use a pair of pliers
and a block of wood as shown, to lever the
pipe out of the union. Considerable force maybe required, but be as careful as possible to
avoid damaging any of the components (see
illustration).
6Release the fuel pump/sender unit’s
retaining ring by turning it anti-clockwise. As
noted above, Ford recommend the use of
service tool 23-038. For those without access
to such equipment, a hammer and drift, or a
pair of slip-jointed pliers, will serve as an
adequate substitute - at least for removal (see
illustration).
7Withdraw the fuel pump/fuel gauge sender
unit, taking care not to bend the float arm. The
float arm is mounted on a spring-loaded
extension, to hold it closely against the
bottom of the tank. Note the sealing ring; this
must be renewed whenever it is disturbed
(see illustrations).
8On refitting, use a new sealing ring, and
ensure that the gauze filter over the base of
the pump pick-up is clean.
9Align the pump/sender unit with the tank
opening, and refit it, ensuring that the float
arm is not bent. Insert the unit so that the float
arm slides correctly up the extension, until the
unit’s top mounting plate can be aligned with
the tank opening and pressed onto the sealing
ring. This may require a considerable amount
of pressure; if so, be careful to avoid
damaging any of the components. The Ford
service tool provides the best way of holding
9 Fuel pump/fuel gauge sender
unit- removal and refitting
4•6 Fuel and exhaust systems
9.4 Unplugging the fuel pump/fuel gauge
sender unit electrical connector (arrowed)9.5 If fuel couplings are difficult to release,
use pliers and a block of wood as shown
to prise pipe end out of union - be careful
not to damage pipes or unions9.6 Fuel pump/fuel gauge sender unit’s
retaining ring can be released using
ordinary tools as shown. Correct service
tool will probably be required on refitting
9.7A Removing fuel pump/fuel gauge
sender unit - take care not to bend float
arm, and note how it is fitted on spring-
loaded extension9.7B Fuel pump/fuel gauge sender unit’s
sealing ring must be renewed whenever it
is disturbed
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the ring square to the tank and turning it at the
same time.
10Maintain the pressure while an assistant
refits and engages the retaining ring. When
the ring is engaged in the tank lugs, turn it
clockwise to tighten it until it is secured.
11The remainder of the refitting procedure is
the reverse of removal. Observe the colour-
coding to ensure that the fuel pipes are
reconnected to the correct unions.
Warning: The fuel system pressure
must be released before any part
of the system is disturbed - see
Section 2. Petrol is extremely
flammable, so take extra precautions when
you work on any part of the fuel system.
Don’t smoke, or allow open flames or bare
light bulbs, near the work area. Don’t work
in a garage where a natural gas-type
appliance (such as a water heater or clothes
dryer) with a pilot light is present. If you spill
any fuel on your skin, rinse it off
immediately with soap and water. When you
perform any kind of work on the fuel
system, wear safety glasses, and have a
Class B type fire extinguisher on hand.
1A fuel tank drain plug is not provided; it is
therefore preferable to carry out the removal
operation when the tank is nearly empty.
Before proceeding, disconnect the battery
negative (earth) lead, and syphon or hand-
pump the remaining fuel from the tank.
Alternatively, disconnect the feed pipe from
the fuel filter (see Chapter 1), and connect a
spare length of hose to this so that when the
ignition is switched on, the fuel pump will
empty the tank into a clean container. If this
approach is adopted, ensure that the
container is large enough to take all the fuel in
the tank, and be careful to take all suitable
precautions to prevent the risk of fire. Note:
Before disconnecting or opening any part of
the fuel system, relieve the residual pressure
(see Section 2), and equalise tank pressure by
removing the fuel filler cap. Also disconnect
the battery negative (earth) lead - see Chap-
ter 5, Section 1.2Unbolt or fold forwards (as appropriate) the
rear seat base cushion (see Chapter 11).
Withdraw from the vehicle’s floor the grommet
covering the fuel pump/sender unit. Unplug
the fuel pump/sender unit’s electrical
connector, and disconnect the fuel return pipe
(coded red) from the unit (see Section 9).
3Raise the rear of the vehicle, and support it
securely on axle stands. Get underneath and
familiarise yourself with the layout of the fuel
tank assembly before proceeding (see
illustration).
Warning: Do not place any part of
your body under a vehicle when
it’s supported only by a jack!
4Either remove the fuel filter, or disconnect
its outlet pipe (see Chapter 1).5Unhook the exhaust system rubber
mountings. Lower the system onto a suitable
support, so that the front downpipe-to-
exhaust manifold joint is not strained, or
remove it completely (see Section 17).
6Unbolt the rear suspension anti-roll bar
mounting clamps (see illustration). Swing the
bar down as far as possible - if clearance is
very restricted, it is advisable to remove the
bar completely (see Chapter 10).
7Disconnect the flexible vent hose from the
moulded plastic fuel tank filler neck as
follows:
(a) On Saloon and Hatchback models, reach
up into the right-hand side aperture in the
rear suspension crossmember, slacken
the clamp, and work the hose off the filler
neck stub. This is a job for someone with
small hands, good tools and a lot of
patience! (see illustration).
10 Fuel tank -
removal and refitting
Fuel and exhaust systems 4•7
4
10.6 Unbolt rear anti-roll bar mounting
clamps (one arrowed) when preparing to
remove the fuel tank10.7A Fuel filler vent hose clamp (arrowed)
is accessible through right-hand side
aperture in rear suspension crossmember
on Saloon and Hatchback models . . .
10.7B . . . on Estate models, it is immediately
above rear suspension anti-roll bar
10.4 Fuel tank assembly
1 Moulded plastic fuel filler
neck
2 Fuel tank
3 Flexible vent hose
4 Roll-over valves
5 Anti-trickle fill valve6 Fuel pump/fuel gauge
sender unit
7 Fuel return pipe union
8 Heat shield
9 Fuel filter
10 Fuel pump-to-filter feed
pipe
11 Fuel tank retaining strap -
2 off
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(b) On Estate models, slacken the clamp
immediately above the rear anti-roll bar,
and work the hose off the filler neck stub
(see illustration).
8Unscrew the six retaining nuts, and
withdraw the exhaust system’s rear heat
shield from the underbody (see illustration).
9Support the tank with a trolley jack or
similar. Place a sturdy plank between the
support and the tank, to protect the tank.
10Unscrew the bolt at the front of each
retaining strap, and pivot them down until
they are hanging out of the way. Note the
earth lead under the left-hand strap’s bolt -
clean the mating surfaces before the tank is
refitted, so that clean, metal-to-metal contact
is ensured.
11Lower the tank enough to unclip the fuel
return pipe (coded red) from its top surface,
then disconnect the charcoal canister’s
vapour hose from the union at the top rear of
the tank (see illustration). If you have any
doubts, clearly label the fuel lines and hoses,
and their respective unions. Plug the hoses, to
prevent leakage and contamination of the fuel
system.
12Remove the tank from the vehicle,
releasing it from the filler neck stub. While the
tank is removed, unhook the retaining straps
(twist them through 90° to do so), and check
that they and their locations in the underbody
are in good condition.
13With the fuel tank removed, the filler neck
can be withdrawn. It is secured by a single
screw in the filler opening, and by two bolts to
the underbody.
14Refitting is the reverse of the removal
procedure.
Warning: Petrol is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. Don’t
smoke, or allow open flames or bare light
bulbs, near the work area. Don’t work in a
garage where a natural gas-type appliance(such as a water heater or clothes dryer)
with a pilot light is present. If you spill any
fuel on your skin, rinse it off immediately
with soap and water. When you perform
any kind of work on the fuel system, wear
safety glasses, and have a Class B type
fire extinguisher on hand.
1Any repairs to the fuel tank or filler neck
should be carried out by a professional who
has experience in this critical and potentially-
dangerous work. Even after cleaning and
flushing of the fuel system, explosive fumes
can remain and ignite during repair of the
tank.
2If the fuel tank is removed from the vehicle,
it should not be placed in an area where
sparks or open flames could ignite the fumes
coming out of the tank. Be especially careful
inside garages where a natural gas-type
appliance is located, because the pilot light
could cause an explosion.
Warning: The fuel system
pressure must be released before
any part of the system is
disturbed - see Section 2. Petrol
is extremely flammable, so take extra
precautions when you work on any part of
the fuel system. Don’t smoke, or allow
open flames or bare light bulbs, near the
work area. Don’t work in a garage where a
natural gas-type appliance (such as a
water heater or clothes dryer) with a pilot
light is present. If you spill any fuel on your
skin, rinse it off immediately with soap and
water. When you perform any kind of work
on the fuel system, wear safety glasses,
and have a Class B type fire extinguisher
on hand.
Note: Refer to illustrations 10.4 and 10.11 for
details.
1Remove the fuel tank (see Section 10).
2Prise the two valves out of the tank, and
remove the anti-trickle fill valve from its
mounting. Take care not to damage the valves
or the tank. Prise out the rubber seals fromthe tank openings, and renew then if they are
worn, distorted, or if either has been leaking.
3If either valve is thought to be faulty, seek
the advice of a Ford dealer as to whether they
can be renewed individually. If not, the
complete valve and pipe assembly must be
renewed.
4Refitting is the reverse of the removal
procedure. Ensure that both roll-over valves
are pressed securely into their seals, so that
there can be no fuel leaks.
1Disconnect the battery negative (earth) lead
- see Chapter 5, Section 1.
2Remove the trim panel from the left-hand
footwell.
3Peel back the sound-insulating material
from the switch, and undo its two retaining
screws (see illustration).
4Unplug the switch electrical connector, and
withdraw the switch.
5Refitting is the reverse of the removal
procedure. Ensure that the switch is reset by
depressing its red button.
These models are equipped with a
Sequential Electronically-controlled Fuel
Injection (SEFI) system. The system is
composed of three basic sub-systems: fuel
system, air induction system and electronic
control system. Note:Refer to illustrations
2.1A and 2.1B of Chapter 6 for further
information on the components of the system.
Fuel system
An electric fuel pump located inside the fuel
tank supplies fuel under pressure to the fuel
rail, which distributes fuel evenly to all
injectors. A filter between the fuel pump and
the fuel rail protects the components of the
system. A pressure regulator controls the
system pressure in relation to inlet tract
depression. From the fuel rail, fuel is injected
14 Fuel injection system/engine
management system - general
information
13 Fuel cut-off switch -
removal and refitting
12 Roll-over valves -
removal and refitting
11 Fuel tank cleaning and repair -
general information
4•8 Fuel and exhaust systems
10.8 Exhaust system must be lowered and
heat shield removed to enable fuel tank
removal - arrows show location of
retaining strap front bolts10.11 Lower fuel tank - do not distort filler
neck stub (A) - and unclip (red-coded) fuel
return pipe (B), then disconnect charcoal
canister’s vapour hose (C)13.3 Fuel cut-off switch retaining screws
(arrowed)
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into the inlet ports, just above the inlet valves,
by four fuel injectors. The system also
includes features such as the flushing of fresh
(ie, cold) fuel around each injector on start-up,
thus improving hot starts.
The amount of fuel supplied by the injectors
is precisely controlled by an Electronic
Control Unit (ECU). The ECU uses the signals
derived from the engine speed/crankshaft
position sensor and the camshaft position
sensor, to trigger each injector separately in
cylinder firing order (sequential injection), with
benefits in terms of better fuel economy and
lower exhaust emissions.
Air induction system
The air system consists of an air filter
housing, an air mass meter, an intake
resonator and plenum chamber, and a throttle
housing. The air mass meter is an information-
gathering device for the ECU; it uses a “hot-
wire” system to send the ECU a constantly-
varying (analogue) voltage signal
corresponding to the volume of air passing
into the engine. Another sensor in the air mass
meter measures intake air temperature. The
ECU uses these signals to calculate the mass
of air entering the engine.
The throttle valve inside the throttle housing
is controlled by the driver, through the
accelerator pedal. As the valve opens, the
amount of air that can pass through the
system increases. The throttle potentiometer
opens further, the air mass meter’s signal
alters, and the ECU opens each injector for a
longer duration, to increase the amount of fuel
delivered to the inlet ports.
Electronic control system
The ECU controls the fuel injection system,
as well as the other sub-systems which make
up the entire engine management system. It
receives signals from a number of information
sensors, which monitor such variables as
intake air mass and temperature, coolant
temperature, engine speed and position,
acceleration/deceleration, and exhaust gas
oxygen content. These signals help the ECU
determine the injection duration necessary for
the optimum air/fuel ratio. These sensors and
associated ECU-controlled relays are located
throughout the engine compartment. For
further information regarding the ECU and its
control of the engine management system,
see Chapter 6.
Idle speed and mixture
adjustment - general
Both the idle speed and mixture are under
the control of the ECU, and cannot be
adjusted. Not only can they not be adjusted,
they cannot even be checked, except with the
use of special diagnostic equipment (see
Chapter 6) - this makes it a task for a Ford
dealer service department. Do notattempt to
“adjust” these settings in any way without
such equipment.
If the idle speed and mixture are thought tobe incorrect, take the vehicle to a Ford dealer
for the complete system to be tested.
On models equipped with a heated
windscreen, an idle-increase solenoid valve is
fitted, which raises the idle speed to
compensate for the increased load on the
engine when the heated windscreen is
switched on. When the valve is open, air from
the plenum chamber bypasses the throttle
housing and idle speed control valve, passing
directly into the inlet manifold through the
union on its left-hand end. The system is
active only for the four minutes that the
heated windscreen circuit is live, and is
supplementary to the main (ECU-controlled)
idle speed regulation.
Warning: Petrol is extremely
flammable, so extra precautions
must be taken when working on
any part of the fuel system. Do
not smoke, or allow open flames or bare
light bulbs, near the work area. Don’t work
in a garage if a natural gas-type appliance
with a pilot light is present. While
performing any work on the fuel system,
wear safety glasses, and have a dry
chemical (Class B) fire extinguisher on
hand. If you spill any fuel on your skin,
rinse it off immediately with soap and
water.
Note: This is an initial check of the fuel delivery
and air induction sub-systems of the engine
management system, to be carried out in
conjunction with the operational check of the
fuel pump (see Section 8), and as part of the
preliminary checks of the complete engine
management system (see Section 3 of
Chapter 6).
1Check the earth wire connections for
tightness. Check all wiring and electrical
connectors that are related to the system.
Loose electrical connectors and poor earths
can cause many problems that resemble
more serious malfunctions.
2Check to see that the battery is fully-
charged. The ECU and sensors depend on an
accurate supply voltage to properly meter the
fuel.
3Check the air filter element - a dirty or
partially-blocked filter will severely impede
performance and economy (see Chapter 1).
4If a blown fuse is found, renew it and see if
it blows again. If it does, search for a short-
circuited wire in the harness related to the
system (see Chapter 6).
5Check the air intake duct from the intake to
the inlet manifold for leaks, which will result in
an excessively-lean mixture. Also check the
condition of the vacuum hoses connected to
the inlet manifold.
6Remove the plenum chamber from the
throttle housing. Check the throttle valve for
dirt, carbon or other residue build-up. If it’sdirty, seek the advice of a Ford dealer - since
the electronic control system is designed to
compensate for factors such as the build-up
of dirt in the throttle housing, it may well be
best to leave it dirty, unless the deposits are
extensive. Note: A warning label on the
housing states specifically that the housing
bore and the throttle valve have a special
coating, and must not be cleaned using
carburettor cleaner, as this may damage it.
7With the engine running, place a
screwdriver or a stethoscope against each
injector, one at a time. Listen through the
screwdriver handle or stethoscope for a
clicking sound, indicating operation.
8If an injector isn’t operating (or sounds
different from the others), turn off the engine,
and unplug the electrical connector from the
injector. Check the resistance across the
terminals of the injector, and compare your
reading with the resistance value listed in this
Chapter’s Specifications. If the resistance
isn’t as specified, renew the injector.
9A rough idle, diminished performance
and/or increased fuel consumption could also
be caused by clogged or fouled fuel injectors.
Fuel additives that can sometimes clean
fouled injectors are available at car accessory
shops.
10The remainder of the system checks
should be left to a dealer service department
or other qualified repair specialist, as there is
a chance that the ECU may be damaged if
tests are not performed properly.
Warning: The fuel system
pressure must be released before
any part of the system is
disturbed - see Section 2. Petrol
is extremely flammable, so take extra
precautions when you work on any part of
the fuel system. Don’t smoke, or allow
open flames or bare light bulbs, near the
work area. Don’t work in a garage where a
natural gas-type appliance (such as a
water heater or clothes dryer) with a pilot
light is present. If you spill any fuel on your
skin, rinse it off immediately with soap and
water. When you perform any kind of work
on the fuel system, wear safety glasses,
and have a Class B type fire extinguisher
on hand.
Throttle housing
Check
1Remove the plenum chamber (see Sec-
tion 4), and verify that the throttle linkage
operates smoothly.
2If the housing bore and valve are dirty
enough for you to think that this might be the
cause of a fault, seek the advice of a Ford
dealer. Do notclean the housing (see the
notes in the checking procedure given in
Section 15).
16 Fuel system components-
check and renewal
15 Fuel injection system/engine
management system - check
Fuel and exhaust systems 4•9
4
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Emissions control systems 6•3
6
2.1B Location of principal fuel injection, ignition and
emissions control system components 2.1A Engine management system, showing fuel injection,
ignition and emissions control sub-systems
1 ECU (Electronic Control Unit)
2 Fuel pump/fuel gauge sender
unit
3 Fuel pump relay
4 Fuel filter
5 Idle speed control valve
6 Air mass meter
7 Air cleaner assembly
8 Fuel pressure regulator
9 Fuel rail
10 Throttle potentiometer
11 Intake air temperature sensor
12 Fuel injector
13 Camshaft position sensor
14 Charcoal canister
15 Charcoal canister-purge
solenoid valve
16 Ignition coil
17 Battery
18 Ignition module - only
separate (from ECU) on
vehicles with automatic
transmission
19 Coolant temperature sensor
20 Oxygen sensor
21 Crankshaft speed/position
sensor
22 Power supply relay
23 Power steering pressure
switch24 Air conditioning compressor
clutch solenoid
25 Service connector - for octane
adjustment
26 Self-test connector - for Ford
STAR tester diagnostic
equipment
27 Diagnosis connector - for Ford
diagnostic equipment FDS
2000
28 Ignition switch
29 Fuel cut-off switch
30 Exhaust Gas Recirculation
(EGR) solenoid valve
31 Exhaust Gas Recirculation
(EGR) valve
32 Exhaust Gas Recirculation
(EGR) exhaust gas pressure
differential sensor
33 Exhaust Gas Recirculation
(EGR) pressure differential
measuring point
34 To inlet manifold
35 Pulse-air filter housing
36 Pulse-air solenoid valve
37 Air conditioning/radiator
electric cooling fan control
38 Automatic transmission
control system - where
applicable1 ECU (Electronic Control Unit)
2 Self-test, diagnosis and service connectors
(left to right)
3 Bulkhead component mounting bracket - manual
transmission - showing from left to right, (EGR) solenoid
valve, pulse-air solenoid valve and (EGR) exhaust gas
pressure differential sensor
4 Bulkhead component mounting bracket - automatic
transmission - showing from left to right, (EGR) solenoid
valve, pulse-air solenoid valve and (EGR) exhaust gas
pressure differential sensor, with separate ignition module
above
5 Throttle housing, including potentiometer
6 Idle speed control valve
7 Intake air temperature sensor
8 Air mass meter
9 Exhaust Gas Recirculation (EGR) valve
10 Coolant temperature sensor
11 Crankshaft speed/position sensor
12 Pulse-air filter housing
13 Oxygen sensor
14 Ignition coil and spark plug (HT) leads
15 Camshaft position sensor
16 Fuel injector(s)
17 Power steering pressure switch
18 Air cleaner assembly
19 Air intake tube and resonators - under left-hand front wing
20 Resonator
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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 power by
uncoupling the battery terminals - see
Section 1 of Chapter 5 - before removing
any of the electronic control system’s
electrical connectors.
(b) When installing a 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) Do not be careless during fault diagnosis.
Even slight terminal contact can invalidate
a testing procedure, and damage one of
the numerous transistor circuits.
(e) Never attempt to work on the ECU, to test
it (with any kind of test equipment), or to
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.
General
The various components of the fuel, ignition
and emissions control systems (not forgetting
the same ECU’s control of sub-systems such
as the radiator cooling fan, 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 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.
Given below is the procedure that would be
followed by a Ford technician to trace a fault
from scratch. Should your vehicle’s engine
management system develop a fault, 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 the comments made in the fourth
paragraph of Section 1 of this Chapter; the
preliminary checks require nothing but care,
patience and a few minor items of equipment,
and may well eliminate the majority of faults.
(a) Preliminary checks
(b) Fault code read-out *
(c) Check ignition timing and base idle
speed. Recheck fault codes to establish
whether fault has been cured or not *
(d) Carry out basic check of ignition system
components. Recheck fault codes to
establish whether fault has been cured or
not *
(e) Carry out basic check of fuel system
components. Recheck fault codes to
establish whether fault has been cured or
not *
(f) If fault is still not located, carry out system
test *
Note:Operations marked with an asterisk
require special test equipment.
Preliminary 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 Part A of
Chapter 2) and bear in mind the possibility
that one of the hydraulic tappets 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/inhibitor system may be responsible.
1The 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.
2If 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.
3Open the bonnet and check the condition
of the battery connections - remake the
connections or renew the leads if a fault is
found (Chapter 5). 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. (In addition to the
earth connection at the engine lifting eye and
that from the transmission to the
body/battery, there is one earth connection
behind each headlight assembly, and one
below the power steering fluid reservoir.)
4Referring to the information given in
Chapter 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.
5Next 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,
3 Diagnosis system -
general information
6•4 Emissions control systems
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coolant or EGR 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).
6Obviously 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.
7Depending 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.
8When the actual damage has been
repaired, ensure that the wiring loom is
rerouted 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.
9Check 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 renewalof that entire section of the loom - see your
local Ford dealer for details.
10If 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
notbe 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.
11Following the accompanying schematic
diagram, and working methodically around
the engine compartment, check carefully that
all vacuum hoses and pipes are securely
fastened and correctly routed, with no signsof cracks, splits or deterioration to cause air
leaks, or of hoses that are trapped, kinked, or
bent sharply enough to restrict air flow (see
illustrations). Check with particular care at all
connections and sharp bends, and renew any
damaged or deformed lengths of hose.
12Working from the fuel tank, via the filter, to
the fuel rail (and including the feed and return),
check the fuel lines, and renew any that are
found to be leaking, trapped or kinked.
13Check 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.
14If there is any doubt about the operation
of the throttle, remove the plenum chamber
from the throttle housing, and check that the
throttle valve moves smoothly and easily from
the fully-closed to the fully-open position and
Emissions control systems 6•5
6
3.11A Vacuum hose routing schematic diagram
A Exhaust Gas Recirculation (EGR) solenoid valve
B Pulse-air solenoid valve
C Exhaust Gas Recirculation (EGR) exhaust gas pressure
differential sensor
D Exhaust Gas Recirculation (EGR) valve
E Charcoal canister-purge solenoid valve
F Restrictor
G Idle-increase solenoid valve - where fitted
H Connection to plenum chamber
J Connection to inlet manifold
K Fuel pressure regulator
L Connection to Positive Crankcase Ventilation (PCV) valve
M Pulse-air filter housing
N Connection to heating/air conditioning system controls
P Charcoal canister
3.11B Installation of vacuum hoses in engine compartment
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back again, as an assistant depresses the
accelerator pedal. If the valve shows any sign
of stiffness, sticking or otherwise-inhibited
movement (and the accelerator cable is
known from the previous check to be in good
condition), spray the throttle linkage with
penetrating lubricant, allow time for it to work,
and repeat the check; if no improvement is
obtained, the complete throttle housing must
be renewed (Chapter 4).
15Unclip the air cleaner cover, and check
that the air filter element and the crankcase
ventilation system filter are not clogged or
soaked. (A clogged air filter will obstruct the
intake 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.
Before refitting the air cleaner cover, check
that the air intake (located under the front left-
hand wing, opening behind the direction
indicator/headlight assembly) is clear. It
should be possible to blow through the intake,
or to probe it (carefully) as far as the rear of
the direction indicator light.
16Start 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.
17Working from the air intake junction at the
inner wing panel, via the air cleaner assembly
and air mass meter, to the resonator, plenum
chamber, 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.
18Similarly, work from the cylinder head, via
the manifold (and not forgetting the related
EGR and pulse-air system components) 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 faultysection of the system, as necessary, to seal
the leak.
19It 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. A
faulty connector should 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.
20Switch 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.
21The final step in these preliminary 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.
Fault code read-out
22As noted in the general comments at the
beginning of this Section, the preliminary
checks outlined above should eliminate the
majority of faults from the engine
management system. If the fault is not yet
identified, the next step is to connect a fault
code reader to the ECU, so that its self-
diagnosis facility can be used to identify the
faulty part of the system; further tests can
then be made to identify the exact cause of
the fault.
23In their basic form, fault code readers are
simply hand-held electronic devices, which
take data stored within an ECU’s memory and
display it when required as two- or three-digit
fault codes. The more sophisticated versions
now available can also control sensors and
actuators, to provide more effective testing;
some can store information, so that a road
test can be carried out, and any faults
encountered during the test can be displayed
afterwards.
6•6 Emissions control systems
3.26 Location and terminal identification of engine management system self-test,
diagnosis and service connectors
1 Power steering fluid reservoir
2 Diagnosis connector - for Ford diagnostic equipment FDS 2000
3 Self-test connector - for fault code read-out - pin 17 is output terminal, pin 48 is input
terminal, pin 40/60 is earth
4 Service connector - for octane adjustment
5 Plug-in bridge - to suit 95 RON fuel
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Ignition timing and base idle
speed check
Note:The following procedure is a check only,
essentially of the ECU. Both the ignition timing
and the base idle speed are controlled by the
ECU. The ignition timing is not adjustable at
all; the base idle speed is set in production,
and should not be altered.
38If the fault code read-out (with any checks
resulting from it) has not eliminated the fault,
the next step is to check the ECU’s control of
the ignition timing and the base idle speed.
This task requires the use of a Ford STAR
tester (a proprietary fault code reader can be
used only if it is capable of inducing the ECU
to enter its “Service Adjustment Programme”),
coupled with an accurate tachometer and a
good-quality timing light. Without this
equipment, the task is not possible; the
vehicle must be taken to a Ford dealer for
attention.
39To make the check, apply the handbrake,
switch off the air conditioning (where fitted)
and any other electrical loads (lights, heated
rear window, etc), then select neutral (manual
transmission) or the “P” position (automatic
transmission). Start the engine, and warm it
up to normal operating temperature. The
radiator electric cooling fan must be running
continuously while the check is made; this
should be activated by the ECU, when
prompted by the tester. Switch off the engine,
and connect the test equipment as directed
by the manufacturer - refer to paragraph 26
above for details of STAR tester connection.
40Raise and support the front of the vehicle
securely, and remove the auxiliary drivebelt
cover (see Chapter 1). Emphasise the two
pairs of notches in the inner and outer rims of
the crankshaft pulley, using white paint. Note
that an ignition timing reference mark is not
provided on the pulley - in the normal
direction of crankshaft rotation (clockwise,
seen from the right-hand side of the vehicle)
the first pair of notches are irrelevant to the
vehicles covered in this manual, while the
second pair indicate Top Dead Centre (TDC)
when aligned with the rear edge of the raised
mark on the sump; when checking the ignition
timing, therefore, the (rear edge of the) sumpmark should appear just before the TDC
notches (see Part A of Chapter 2, Section 4,
for further information if required).
41Start the engine and allow it to idle. Work
through the engine-running test procedure
until the ECU enters its “Service Adjustment
Programme” - see paragraph 35 above.
42Use the timing light to check that the
timing marks appear approximately as
outlined above at idle speed. Do not spend
too much time on this check; if the timing
appears to be incorrect, the system may have
a fault, and a full system test must be carried
out (see below) to establish its cause.
43Using the tachometer, check that the
base idle speed is as given in the
Specifications Section of Chapter 4.
44If the recorded speed differs significantly
from the specified value, check for air leaks,
as described in the preliminary checks
(paragraphs 15 to 18 above), or any other
faults which might cause the discrepancy.
45The base idle speed is set in production
by means of an air bypass screw (located in
the front right-hand corner of the throttle
housing) which controls the amount of air that
is allowed to pass through a bypass passage,
past the throttle valve when it is fully closed in
the idle position; the screw is then sealed with
a white tamperproof plug (see illustration). In
service, the idle speed is controlled by the
ECU, which has the ability to compensate for
engine wear, build-up of dirt in the throttle
housing, and other factors which might
require changes in idle speed. The air bypass
screw setting should not, therefore, be
altered. If any alterations are made, a blue
tamperproof plug must be fitted, and the
engine should be allowed to idle for at least
five minutes on completion, so that the ECU
can re-learn its idle values.
46When both checks have been made and
the “Service Adjustment Programme” is
completed, follow the tester instructions to
return to the fault code read-out, and
establish whether the fault has been cured or
not.
Basic check of ignition system
47If the checks so far have not eliminated
the fault, the next step is to carry out a basic
check of the ignition system components,
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.
Basic check of fuel system
48If the checks so far have not eliminated
the fault, the next step is to carry out a basic
check of the fuel system components.
49Assuming that the preliminary checks
have established that the fuel pump is
operating correctly, that the fuel filter isunlikely to be blocked, and also that there are
no leaks in the system, the next step is to
check the fuel pressure (see Chapter 4). If this
is correct, check the injectors (see Chapter 4)
and the Positive Crankcase Ventilation system
(see Chapter 1).
System test
50The final element of the Ford testing
procedure is to carry out a system test, using
a break-out box - this is a device that is
connected between the ECU and its electrical
connector, so that the individual circuits
indicated by the fault code read-out can be
tested while connected to the system, if
necessary with the engine running. In the case
of many of the system’s components, this
enables their output voltages to be measured
- a more accurate means of testing.
51In addition to the break-out box and the
adaptors required to connect it, several items
of specialist equipment are needed to
complete these tests. This puts them quite
beyond the scope of many smaller dealers, let
alone the DIY owner; the vehicle should be
taken to a Ford dealer for attention.
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.
General
ECU (Electronic Control Unit)
1This component is the heart of the entire
engine management system, controlling the
fuel injection, ignition and emissions control
systems. It also controls sub-systems such as
the radiator cooling fan, air conditioning and
automatic transmission, where appropriate.
Refer to Section 2 of this Chapter for an
illustration of how it works.
Air mass meter
2This uses a “hot-wire” system, sending the
ECU a constantly-varying (analogue) voltage
signal corresponding to the mass of air
passing into the engine. Since air mass varies
with temperature (cold air being denser than
warm), measuring air mass provides the ECU
with a very accurate means of determining the
correct amount of fuel required to achieve the
ideal air/fuel mixture ratio.
Crankshaft speed/position sensor
3This is an inductive pulse generator bolted
(in a separate bracket) to the cylinder
block/crankcase, to scan the ridges between
36 holes machined in the inboard (right-hand)
face of the flywheel/driveplate. As each ridge
4 Information sensors -
general information, testing,
removal and refitting
6•10 Emissions control systems
3.45 Throttle housing air bypass screw is
sealed on production with a white
tamperproof plug (arrowed)
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General information
1This system consists of the pulse-air
solenoid valve, the pulse-air valve itself,
contained in the filter housing, and the piping
- see illustration 2.1A. It injects filtered air
directly into the exhaust ports, using the
pressure variations in the exhaust gases to
draw air through from the filter housing; air will
flow into the exhaust only when its pressure is
below atmospheric. The pulse-air valve can
allow gases to flow only one way, so there is
no risk of hot exhaust gases flowing back into
the filter.
2The system’s primary function is raise
exhaust gas temperatures on start-up, thus
reducing the amount of time taken for the
oxygen sensor and catalytic converter to
reach operating temperature. Until this
happens, the system reduces emission of
unburned hydrocarbon particles (HC) and
carbon monoxide (CO) by ensuring that a
considerable proportion of these substances
remaining in the exhaust gases after
combustion are burned up, either in the
manifold itself or in the catalytic converter.
3To ensure that the system does not upset
the smooth running of the engine under
normal driving conditions, it is linked by the
pulse-air solenoid valve to the ECU, so that it
only functions during engine warm-up, when
the oxygen sensor is not influencing the
fuel/air mixture ratio.
Checking
4Poor idle, stalling, backfiring and poor
driveability can be caused by a fault in the
system.
5Inspect the vacuum pipe/hose connected
between the filter housing and the solenoid
valve for kinks, leaks and cracks along its
entire length. Repair or renew as necessary.
6Inspect the filter housing and piping. If
either is cracked or damaged, renew it.7If the pulse-air solenoid valve is thought to
be faulty, unplug its electrical connector and
disconnect its vacuum hoses. Connect a
battery directly across the valve terminals,
and check that air can flow through the valve
passages when the solenoid is thus
energised, and that nothing can pass when
the solenoid is not energised. Alternatively,
connect an ohmmeter to measure the
resistance across the valve terminals, and
compare this reading to the one listed in the
Specifications Section at the beginning of this
Chapter. Renew the solenoid valve if it is
faulty.
8Further testing should be left to a dealer
service department.
Component renewal
Pulse-air solenoid valve
Note:This component can be identified by its
smaller top and its clip fastening. Do not
confuse it with the adjacent EGR solenoid
valve, especially when reconnecting vacuum
hoses.
9Disconnect the battery negative (earth) lead
- see Section 1 of Chapter 5.
10Remove the air mass meter and resonator
- refer to Chapter 4. If better access is
required, remove the plenum chamber also
(see illustration).
11Releasing its wire clip, unplug the
electrical connector, then use a small
screwdriver to release the clip securing the
valve to the bulkhead mounting bracket.Withdraw the valve, then label and disconnect
the two vacuum hoses.
12Refitting is the reverse of the removal
procedure; ensure that the hoses are correctly
reconnected.
Pulse-air filter housing
Note:This component, and those around it,
will be very hot when the engine is running.
Always allow the engine to cool down fully
before starting work, to prevent the possibility
of burns.
13Raise the front of the vehicle, and support
it securely on axle stands. Disconnect the
vacuum hose from the base of the filter
housing (see illustration).
14Disconnect the battery negative (earth)
lead - see Section 1 of Chapter 5.
15Unbolt the resonator support bracket
from the engine compartment front
crossmember, slacken the two clamp screws
securing the resonator to the air mass meter
and plenum chamber hoses, then swing the
resonator up clear of the thermostat housing
(see Chapter 4).
16Remove the screws securing the filter
housing to the piping, unscrew the mounting
bolt, then withdraw the housing (see
illustration).
17To dismantle the filter housing, undo the
four screws and separate the top from the
base of the housing; extract the foam filter,
and clean it in a suitable solvent (see
illustrations). If any of the housing’s
7 Pulse-air system -
general information
Emissions control systems 6•17
6
7.17A Remove four screws to release filter
housing top from base . . .7.17B . . .and withdraw foam filter for
cleaning, if required - note valve in base of
housing
7.10 Pulse-air solenoid valve (arrowed) is
located on bulkhead mounting bracket. It
can be identified by its smaller top and its
clip fastening - do not confuse it with the
adjacent EGR solenoid valve7.13 Disconnect vacuum hose from base
of pulse-air filter housing . . .7.16 . . . undo screws “A” to disconnect
piping from housing, and mounting
bolt “B” to release housing
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