service FORD SIERRA 1991 2.G Fuel And Exhaust Systems Fuel Injection Workshop Manual

manual mixture adjustment is possible.
On models with a catalytic converter, an
evaporative emission control (EVAP) system is
fitted. This prevents the release of fuel vapour
into the atmosphere. With the ignition
switched off, vapours from the fuel tank are
fed to a carbon canister, where they are
absorbed. When the engine is started, the
EEC IV module opens a purge solenoid valve,
and the fuel vapours are fed into the inlet
manifold and mixed with fresh air. This cleans
the carbon filter. A blow-back valve prevents
inlet air being forced back into the fuel tank.
A fuel pump inertia switch is fitted. This
switch breaks the electrical circuit to the fuel
pump in the event of an accident or similar
impact, cutting off the fuel supply to the engine.
A “limited operation strategy” (LOS) means
that the vehicle will still be driveable, albeit at
reduced power and efficiency, in the event of
a failure in the EEC IV module or its sensors.
1.6 and 1.8 litre (R6A type) CVH models
The fuel injection system fitted to these
models is under the overall control of an EEC
IV engine management system which also
controls the ignition timing.
Fuel is supplied from the rear-mounted fuel
tank by an electric fuel pump which is integral
with the fuel level sender unit mounted inside
the fuel tank. Fuel passes via a fuel filter to the
Central Fuel Injection (CFI) unit. A fuel
pressure regulator, mounted on the CFI unit,
maintains a constant fuel pressure to the fuel
injector. Excess fuel is returned from the
regulator to the tank.
The CFI unit, resembling a carburettor,
houses the throttle valve, throttle valve control
motor, throttle position sensor, air charge
temperature sensor, fuel injector, and
pressure regulator.
The duration of the electrical pulse supplied
to the fuel injector determines the quantity of
fuel injected, and pulse duration is computed
by the EEC IV module on the basis of
information received from the various sensors.
The fuel injector receives a pulse twice per
crankshaft revolution under normal operating
conditions, and once per crankshaft
revolution under engine idle conditions. A
ballast resistor is used in the fuel injector
control circuit on 1.6 litre engines.
Inlet air passes through the air cleaner into
the CFI unit. The volume of air entering the
engine is calculated by the EEC IV module from
information supplied by various sensors. These
sensors include the air charge temperature
sensor and throttle position sensor, mounted in
the CFI unit; a crankshaft speed/position
sensor which supplies information on engine
speed; and a manifold absolute pressure (MAP)
sensor which measures the pressure of the air
entering the engine.
Additional sensors inform the EEC IV module
of engine coolant temperature, and vehicle
speed (from a gearbox-mounted sensor).
An exhaust gas oxygen (HEGO) sensor
enables the EEC IV module to control the
fuel/air mixture to suit the operating
parameters of the catalytic converter. No
manual mixture adjustment is possible.
Idle speed is controlled by a throttle valvecontrol motor, which controls the position of
the throttle valve under conditions of idling,
deceleration/part-throttle, and engine start-up
and shut-down.
On 1.6 litre engines, a pulse-air system is
fitted to reduce the exhaust gas emissions
during engine warm-up. The system is con-
trolled by a vacuum-operated valve, which is
operated by the EEC IV module via a solenoid.
The system introduces air into the exhaust
manifold to increase the exhaust gas
temperature, which oxidises more of the
pollutants, and brings the catalyst up to
working temperature more quickly. The
system operates until the catalyst reaches
operating temperature, when the control
solenoid shuts off the system.
On 1.8 litre engines, an exhaust gas
recirculation (EGR) system is used to
recirculate a small amount of exhaust gas into
the inlet manifold. This process lowers the
combustion temperature, resulting in a
reduction of NOx (oxides of nitrogen)
emissions. The EGR system is controlled by
the EEC IV module in conjunction with an
Electronic Pressure Transducer (EPT) and an
Electronic Vacuum Regulator (EVR).
On certain models, an evaporative emission
control system may be fitted. This prevents
the release of fuel vapour into the
atmosphere. With the ignition switched off,
vapours from the fuel tank are fed to a carbon
canister, where they are absorbed. When the
engine is started the EEC IV module opens a
purge solenoid valve, and the fuel vapours are
fed into the inlet manifold and mixed with
fresh air. This cleans the carbon filter. A blow-
back valve prevents inlet air being forced
back into the fuel tank.
A fuel pump inertia switch is fitted. This
switch breaks the electrical circuit to the fuel
pump in the event of an accident or similar
impact cutting off the fuel supply to the engine.
A “limited operation strategy” (LOS) means
that the vehicle will still be driveable, albeit at
reduced power and efficiency, in the event of
a failure in the EEC IV module or its sensors.
Precautions
Many of the procedures in this Chapter
require the removal of fuel lines and
connections which may result in some fuel
spillage. Before carrying out any operation on
the fuel system refer to the precautions given
in “Safety first!” at the beginning of this
Manual and follow them implicitly. Petrol is a
highly dangerous and volatile liquid and the
precautions necessary when handling it
cannot be overstressed.
Residual pressure will remain in the fuel
lines long after the vehicle was last used,
therefore extra care must be taken when
disconnecting a fuel line hose. Loosen any
fuel hose slowly to avoid a sudden release of
pressure which may cause fuel spray. As an
added precaution place a rag over each union
as it is disconnected to catch any fuel which is
forcibly expelled.
Certain adjustment points in the fuel system
(and elsewhere) are protected by
“tamperproof” caps, plugs or seals. The
purpose of such tamperproofing is todiscourage, and to detent, adjustment by
unqualified operators.
In some EEC countries (though not yet in
the UK) it is an offence to drive a vehicle with
missing or broken tamperproof seals. Before
disturbing a tamperproof seal, satisfy yourself
that you will not be breaking local or national
anti-pollution regulations by doing so. Fit a
new seal when adjustment is complete when
this is required by law.
Do not break tamperproof seals on a
vehicle which is still under warranty.
Catalytic converter - precautions
The catalytic converter is a reliable and simple
device which needs no maintenance in itself,
but there are some facts of which an owner
should be aware if the converter is to function
properly for the full service life.
a)DO NOT use leaded petrol in a car
equipped with a catalytic converter the
lead will coat the precious metals,
reducing their converting efficiency and
will eventually destroy the converter.
b)Always keep the ignition and fuel systems
well-maintained in accordance with the
manufacturers schedule, ensure that the
air cleaner filter element, the fuel filter
(where fitted) and the spark plugs are
renewed at the correct interval if the inlet
air/fuel mixture is allowed to become too
rich due to neglect, the unburned surplus
will enter and burn in thecatalytic
converter, overheating the element and
eventually destroying the converter.
c)If the engine develops a misfire, do not
drive the car at all (or at least as little as
possible) until the fault is cured - the
misfire will allow unburned fuel to enter
the converter, which will result in
overheating, as noted above.
d)DO NOT push- or tow-start the car - this
will soak the catalytic converter in
unburned fuel, causing it to overheat when
the engine does start - see b) above.
e)DO NOT switch off the ignition at high
engine speeds - if the ignition is switched
off at anything above idle speed,
unburned fuel will enter the (very hot)
catalytic converter, with the possible risk
of igniting on the element and damaging
the converter.
f)DO NOT use fuel or engine oil additives -
these may contain substances harmful to
the catalytic converter.
g)DO NOT continue to use the car if the
engine burns oil to the extent of leaving a
visible trail of blue smoke - the unburned
carbon deposits will clog the converter
passages and reduce the efficiency; in
severe cases the element will overheat.
h)Remember that the catalytic converter
operates at very high temperatures - hence
the heat shields on the car’s underbody
and the casing will become hot enough to
ignite combustible materials which brush
against it - DO NOT, therefore, park the car
in dry undergrowth, over long grass or
piles of dead leaves.
i)Remember that the catalytic converter is
FRAGILE, do not strike it with tools during
servicing work, take great care when
Fuel and exhaust systems - fuel injection 4B•3
4B

working on the exhaust system, ensure
that the converter is well clear of any
jacks or other lifting gear used to raise the
car and do not drive the car over rough
ground, road humps, etc., in such a way
as to “ground” the exhaust system.
j)In some cases, particularly when the car is
new and/or is used for stop/start driving, a
sulphurous smell (like that of rotten eggs)
may be noticed from the exhaust. This is
common to many catalytic converter-
equipped cars and seems to be due to the
small amount of sulphur found in some
petrols reacting with hydrogen in the
exhaust to produce hydrogen sulphide
(H2S) gas; while this gas is toxic, it is not
produced in sufficient amounts to be a
problem. Once the car has covered a few
thousand miles the problem should
disappear - in the meanwhile a change of
driving style or of the brand of petrol used
may effect a solution.
k)The catalytic converter, used on a well-
maintained and well-driven car, should
last for between 50 000 and 100 000
miles - from this point on, careful checks
should be made at all specified service
intervals of the CO level to ensure that the
converter is still operating efficiently - if
the converter is no longer effective it must
be renewed.
EEC IV module - warning
Following disconnection of the battery, the
information stored in the EEC IV module
memory will be erased. After reconnecting the
battery, the engine should be allowed to idle for
three minutes. Once the engine has reached
normal operating temperature, the idle speed
should be increased to 1200 rpm and
maintained for approximately 2 minutes, which
will allow the module to “re-learn” the optimum
idle values. It may be necessary to drive the
vehicle in order for the module to “re-learn” the
values under load. The module should complete
its learning process after approximately 5 miles
(8 kilometres) of varied driving.
Refer to Chapter 1, Section 38.
2.0 litre SOHC models
1Disconnect the battery negative lead.
2Depress the locking clip on the airflow
meter wiring plug and disconnect the plug.
Pull on the plug, not the wiring.
3Loosen the securing clip and disconnect
the air inlet hose from the airflow meter.
4Release the four securing clips and lift off
the air cleaner lid with the airflow meter.
5Remove the left-hand front wheel arch liner.
6Working under the wheel arch, unscrew the
three air cleaner securing nuts and washers.
7Disconnect the air inlet tube, and withdrawthe air cleaner from the engine compartment.
8Refitting is a reversal of removal.
2.0 litre DOHC models
9Disconnect the battery negative lead.
10Disconnect the wiring plug from the idle
speed control valve at the front of the plenum
chamber.
11Loosen the clamp, and detach the air inlet
hose from the air inlet tubing.
12Unscrew the securing nut, and release the
air inlet tube from the bracket on the engine
compartment front panel.
13Release the air cleaner lid securing clips,
then lift away the air inlet tube, plenum
chamber and air cleaner lid as an assembly,
disconnecting the breather hose from the air
inlet tube.
14Lift out the air cleaner element then wipe
the inside of the air cleaner lid and casing clean.
15Remove the left-hand front wheel arch liner.
16Working under the wheel arch, unscrew the
three air cleaner securing nuts and washers.
17Disconnect the air inlet tube, and
withdraw the air cleaner from the engine
compartment.
18Refitting is a reversal of removal.
1.6 and 1.8 litre (R6A type) CVH
models
1.6 litre
19Remove the screws from the top of the air
cleaner cover.
20Disconnect the cold air inlet hose from the
air cleaner spout or the inlet on the front body
panel. The hose is secured by toggle clips.
21Disconnect the hot air inlet hose from the
air cleaner spout or the hot air shroud on the
exhaust manifold.
22Where applicable, remove the screw
securing the air cleaner body to the camshaft
cover.
23Withdraw the air cleaner and disconnect
the breather hose from the camshaft cover.
24Refitting is a reversal of removal, ensure
the disturbed hoses are securely connected.
1.8 litre
25Undo the two nuts, lift off the air cleaner
cover, and remove the element.26Disconnect the engine breather hose and
the oil separator hose, then undo the three
nuts and lift up the air cleaner casing (see
illustrations).
27Disconnect the yellow striped vacuum
hose from the underside of the casing, detach
the air inlet hose, and remove the air cleaner
assembly.
28Refitting is a reversal of removal, ensuring
all hoses are correctly attached.
1Disconnect the battery negative lead.
2Remove the air cleaner assembly.
3Position a suitable container (or a sufficient
quantity of absorbent cloth) beneath the fuel
inlet connection on the CFI unit.
4Use an open-ended spanner on the flats of
the inlet union screwed into the CFI unit, to
prevent it from turning while the inlet pipe
union is loosened (see illustration). Allow all
pressure/fuel seepage to dissipate before fully
unscrewing the union if it is to be
disconnected, or tightened if another part of
the system is to be worked on.
4Fuel system (1.6 and 1.8 litre
(R6A type) CVH) - depressurisation
3Air cleaner - removal and
refitting
2Air cleaner element - renewal
4B•4Fuel and exhaust systems - fuel injection
3.26b Air cleaner casing attachments - 1.8
litre (R6A) CVH
A Casing retaining nuts (arrowed)
B Vacuum hose (arrowed)
3.26a Air cleaner cover and hose
attachments - 1.8 litre (R6A) CVH
A Cover retaining nuts
B Engine breather hose
C Oil separator hose
Remember to depressurise the
fuel system before loosening any
connections.
Refer to the precautions in
Section 1 before proceeding. The fuel
system will remain pressurised after the
engine is switched off.
4.4 CFI unit fuel inlet union (arrowed)

4Note the locations of the two solenoid
pipes, and the orientation of the solenoid, to
assist with refitting.
5Disconnect the two pipes from the
solenoid, and withdraw the solenoid from its
location.
6Refitting is a reversal of removal. Ensure
that the solenoid pipes are correctly
reconnected, and that the solenoid is
correctly orientated, as noted before removal.
1.6 and 1.8 litre (R6A type) CVH
models
7On 1.6 litre engines, the purge solenoid is
located to the rear of the carbon canister, on
the right-hand side of the engine
compartment. On 1.8 litre engines, the
location varies according to model and
equipment, but can be traced by following the
solenoid pipes back from the carbon canister
(see illustration).
8Proceed as detailed in paragraphs 2 to 6
inclusive.
Note: Do not touch the tip of the HEGO
sensor as this will drastically shorten its
service life.
Note: A new sealing ring should be used on
refitting.
Removal
1Ensure that the engine and the exhaust
system are cold.
2Disconnect the battery negative lead.
3Apply the handbrake, then jack up the front
of the vehicle, and support it securely on axle
stands (see “Jacking and Vehicle Support”).
4Disconnect the sensor wiring plug halves
by releasing the locktabs and pulling on the
plug halves, not the wiring.
5Where fitted, slide the heat shield from the
sensor (see illustration).
6Unscrew the sensor from the exhaust
downpipe, and recover the sealing ring. Do
not touch the tip of the sensor if it is to be
refitted.
Refitting
7Commence refitting by ensuring that the
sensor threads and the corresponding
threads in the downpipe are clean.
8Refit the sensor using a new sealing ring,
and tighten it to the specified torque.
9Further refitting is a reversal of removal, but
on completion start the engine, and check for
leaks around the sensor sealing ring.
2.0 litre SOHC models
1Refer to Chapter 4 Part A, Section 26, but
note the following points.
2Ignore the references to removal and
refitting of the air cleaner and hot air pick-up
pipe, and note that a heat shield is fitted in
place of the hot air shroud.
3Note the location of the inlet manifold
bracing strut which is secured to one of the
manifold studs by an extra nut.
2.0 litre DOHC models
Note: A new manifold gasket must be used on
refitting.
4Disconnect the battery negative lead.
5Disconnect the wiring plug from the idle
speed control valve at the front of the plenum
chamber.
6Loosen the clamp, and detach the air inlet
hose from the air inlet tubing.
7Unscrew the securing nut, and release the
air inlet tube from the bracket on the engine
compartment front panel.
8Release the air cleaner lid securing clips,
then lift away the air inlet tube, plenum
chamber and air cleaner lid as an assembly
disconnecting the breather hose from the air
inlet tube.
9On models with a catalytic converter,
disconnect the exhaust gas oxygen sensor
wiring plug.
10Unscrew the securing nuts, and
disconnect the exhaust downpipe from the
manifold. Recover the gasket. Support the
exhaust downpipe from underneath the
vehicle (eg with an axle stand) to avoid placing
unnecessary strain on the exhaust system.
11Unscrew the six securing nuts, and lift the
manifold from the cylinder head. Recover the
gasket.
12Refitting is a reversal of removal, bearing
in mind the following points.
13Ensure that all mating faces are clean, and
use a new gasket.
14Tighten the manifold securing nuts and
the downpipe securing nuts progressively to
the specified torque (where given).
1.6 and 1.8 litre (R6A type) CVH
models
Note. A new manifold gasket and downpipe
gaskets must be used on refitting.
15Disconnect the battery negative lead.16Remove the air cleaner and, where fitted,
pull the hot-air pick-up pipe from the exhaust
manifold hot-air shroud.
17On 1.6 litre engines, remove the pulse-air
delivery tubing.
18Remove the securing bolts, and withdraw
the hot-air shroud from the manifold.
19Disconnect the exhaust gas oxygen
sensor wiring plug. Unscrew the securing
nuts, and disconnect the exhaust downpipe
from the manifold. Recover the gasket.
Support the exhaust downpipe from
underneath the vehicle (eg with an axle stand)
to avoid placing unnecessary strain on the
exhaust system.
20Unscrew the securing nuts, and lift the
manifold from the cylinder head. Recover the
gasket.
21Refitting is a reversal of removal, bearing
in mind the following points.
22Ensure that all mating faces are clean, and
renew all gaskets.
23Tighten the manifold securing nuts
progressively to the specified torque, and
similarly tighten the exhaust downpipe
securing nuts.
1Refer to Chapter 4 Part A, Section 27.
2On all models except 2.0 litre SOHC,
flanged joints incorporating gaskets may be
used to join exhaust sections on certain
models. Where applicable, renew the gaskets
on refitting.
3On models fitted with a catalytic converter,
disconnect the battery negative lead and
disconnect the exhaust gas oxygen (HEGO)
sensor wiring plug before removing the
downpipe.
37Exhaust system - inspection,
removal and refitting
36Exhaust manifold - removal
and refitting
35Exhaust gas oxygen (HEGO)
sensor (2.0 litre DOHC/1.6 &
1.8 litre (R6A type) CVH) -
removal and refitting
Fuel and exhaust systems - fuel injection 4B•15
4B
35.5 Sliding the heat shield from the
exhaust gas oxygen sensor34.7 Carbon canister-purge solenoid
location (arrowed) - 1.6/1.8 litre (R6A) CVH