octane FORD SIERRA 1992 2.G Engine Electrical Systems Workshop Manual

10The distributor cap (except on 1.6 and 1.8
litre CVH (R6A type) engines) and the HT
leads should be cleaned and checked at the
specified intervals. To test the HT leads,
remove them together with the distributor
cap, then connect an ohmmeter to the end of
each lead and its appropriate terminal within
the cap in turn (see illustration). If the
resistance of any lead is greater than the
maximum given in the Specifications, check
that the lead connection in the cap is good
before renewing the lead.
Refitting
11Before fitting the spark plugs, check that
the threaded connector sleeves are tight and
that the plug exterior surfaces are clean. As
the plugs incorporate taper seats also make
sure that the threads and seats are clean.
12On DOHC models before refitting thespark plugs, coat their threads with suitable
antiseize compound, taking care not to
contaminate the electrodes.
13Screw in the spark plugs by hand, then
tighten them to the specified torque. Do not
exceed the torque figure.
14Push the HT leads firmly onto the spark
plugs, and where applicable refit the air
cleaner and/or inlet hose.Testing
All models except 1.6 and 1.8 litre
CVH (R6A type)
1The coil is located on the left-hand side of
the engine compartment and is retained by a
metal strap (see illustration). It is of high
output type and the HT tower should be kept
clean at all times to prevent possible arcing.
Bosch and Femsa coils are fitted with
protective plastic covers and Polmot coils are
fitted with an internal fusible link.
2To ensure that the correct HT polarity at the
spark plugs, the LT coil leads must always be
connected correctly. The black lead must
always be connected to the terminal marked +
115, and the green lead to the terminal
marked /1. Incorrect connections can cause
poor starting, misfiring, and short spark plug
life.
3To test the coil first disconnect the LT and
HT leads. Connect an ohmmeter betweenboth LT terminals and check that the primary
winding resistance is as given in the
Specifications. Connect the ohmmeter
between the HT terminal and either LT
terminal and check that the secondary
winding resistance is as given in the
Specifications. If either winding resistance is
not as specified, the coil should be renewed.
Reconnect the LT and HT leads on
completion.
1.6 and 1.8 litre (R6A type) CVH
models
4The coil fitted to these models is located
towards the front right-hand side of the
cylinder block (see illustration).
5Testing of the coil should be entrusted to a
Ford dealer or a suitable specialist.
Removal
All models except 1.6 and 1.8 litre
CVH (R6A type)
6Disconnect the battery negative lead,
7Disconnect the LT and HT leads from the
coil (see illustration).
8Remove the securing screw(s) and detach
the coil and strap assembly from the body
panel. Note that on models with the ESC
system, the coil strap is secured by the top
ESC module securing screw. On certain
models with the ESC II or EEC IV systems, an
“octane adjustment” service lead may be
connected to one of the coil securing screws.
On 2.0 litre DOHC fuel-injected models, the
coil/ignition module heat shield must be
removed for access to the coil securing bolts.
The heat shield is secured by two screws.
Note that on certain models, an earthing lead
12Coil - testing, removal and
refitting
Engine electrical systems 5•13
5
11.10 Method of testing an HT lead with an
ohmmeter
12.4 Ignition coil (A) and suppressor (B)
viewed from under vehicle (shroud removed)12.7 Disconnecting the HT lead from the
coil
12.1 Ignition coil - CVH model. Plastic
cover arrowed
11.9c Adjusting a spark plug gap using a
special tool11.9b Measuring a spark plug gap using a
wire gauge

Refitting
13Commence refitting by checking that No 1
cylinder is still at the firing point. The relevant
timing marks should be aligned. If the engine
has been turned whilst the distributor has
been removed, check that No 1 cylinder is on
its firing stroke by removing the No 1 cylinder
spark plug and placing a finger over the plug
hole. Turn the crankshaft until compression
can be felt, which indicates that No 1 piston is
rising on its firing stroke. Continue turning the
crankshaft until the relevant timing marks are
in alignment.
14Turn the rotor arm to the position noted in
paragraph 11. If a new distributor is being
fitted, and no alignment marks are present,
transfer the marks from the old distributor to
the new distributor.
15Hold the distributor directly over the
aperture in the cylinder block with the
previously made marks on the distributor
body and cylinder block aligned, then lower
the distributor into position. Again, if a new
distributor is being fitted, transfer the
alignment mark from the old distributor body
to the new distributor body. As the skew gear
drive meshes, the rotor arm will turn
anti-clockwise.
16With the distributor fitted and the marks
on the distributor body and cylinder block
aligned, check that the rotor arm is positioned
as described in paragraph 7 -if not, withdraw
the distributor, re-position the driveshaft and
try again.
17Refit the clamp, then insert and tighten
the bolt. Do not fully tighten the bolt at this
stage.
18Refit the distributor wiring plug, and
where applicable reconnect the vacuum pipe,
and refit the dust cover and/or rotor arm.
19Refit the distributor cap, and reconnect
the HT leads to the spark plugs and coil.
Ensure that the leads are refitted to their
correct cylinders.
20Where applicable, refit the screening can
to the top of the distributor and reconnect the
earth strap. On fuel injection models,
reconnect the air inlet hose, ensuring that the
clips are correctly aligned (refer to illustration,
Section 15, Chapter 4, PartB).21Reconnect the battery negative lead.
22Check and if necessary adjust the ignition
timing.
Early “Economy” models
Removal
23Removal of the distributor fitted to these
models is a similar process to that described
above.
Refitting
24Turn the crankshaft to bring No 1 cylinder
to the firing point, with the 16º BTDC mark on
the crankshaft pulley aligned with the pointer
on the crankshaft front oil seal housing, as
described above.
25Fit the new distributor to the engine as
described above, then proceed as follows.
26Cut the original distributor wiring plug
from the wiring loom. Make the cut close to
the connector.
27Strip back 10 mm of insulation from each
of the wires on the wiring loom, and on the
adapter loom supplied with the new
distributor.
28Solder the adapter loom wires to the
corresponding identically coloured wires in
the main loom.
29Carefully insulate each individual soldered
joint using insulating tape, then apply tape to
cover the join between the looms.
30Fit a new distributor cap (and screening
can, where applicable), and connect the HT
leads.31Connect the adapter loom to the
distributor.
32Start the engine, and adjust the ignition
timing to the value given in the Specifications
at the beginning of this Chapter. Work as
described above whilst noting that the
vacuum pipe must be left connected.
Note: During production the ignition timing is
accurately set using a microwave process,
and sealant is applied to the distributor clamp
bolt. Because the electronic components
require no maintenance, checking the ignition
timing does not constitute part of the routine
maintenance schedule, and the procedure is
therefore only necessary after removal and
refitting of the distributor. A timing light will be
required for this procedure. For details of
ignition timing adjustment in order to operate
vehicles on unleaded petrol refer to the
appropriate Section of this Chapter.
All models except 2.0 litre DOHC
1Before checking the ignition timing, the
following conditions must be met:
a)The engine must be at normal operating
temperature
b)Where applicable, the vacuum pipe to the
distributor vacuum unit or electronic
module (as applicable) must be
disconnected from the vacuum unit or
electronic module and plugged
c)The idle speed must be below 900 rpm
(isolate “idle speed adjustment” wire if
necessary)
d)Any earthed “octane adjustment” wires
must be temporarily isolated
2Wipe clean the crankshaft pulley timing
marks and the pointer on the crankshaft front
oil seal housing. Note that two alternative
types of pulley may be fitted (see
illustration).The desired timing values are
given in the Specifications. If necessary, use
white paint or chalk to highlight the relevant
timing mark(s) (see illustration).
3Connect a stroboscope timing light to the
No 1 cylinder HT lead, following the
manufacturer’s instructions.
4With the engine idling at normal operating
temperature, point the timing light at the
marks on the crankshaft pulley, and check
that the appropriate timing mark appears
stationary in line with the timing cover pointer.
Take care not to get the timing light leads,
clothing etc tangled in the cooling fan blades
or other moving parts of the engine.
5If adjustment is necessary, stop the engine,
slacken the distributor clamp bolt, and turn
the distributor body slightly. Turn the
distributor body clockwise to retard the
ignition timing (move the timing closer to TDC)
and anti-clockwise to advance the timing.
16Ignition timing (OHC models)
- adjustment
Engine electrical systems 5•17
5
15.12 Removing distributor driveshaft O-
ring - Motorcraft distributor15.10 Unscrewing distributor clamp bolt -
Bosch distributor
16.2a Highlighted timing marks - SOHC
engine with cast crankshaft pulley

Note that the required distributor body
movement will be half of the required
crankshaft movement (ie an adjustment of 5º
in ignition timing will require the distributor
body to be turned 2º. Tighten the clamp bolt
and re-check the timing.
6On models with inductive discharge ignition
systems, the mechanical and vacuum
advance mechanisms can be checked as
follows. On all other models, proceed to
paragraph 10.
7With the engine idling, timing light
connected, and vacuum pipe disconnected as
described in the preceding paragraphs,
increase the engine speed to approximately
2000 rpm (if desired, connect a tachometer to
the engine in accordance with the
manufacturer”s instructions). Note the
approximate distance which the relevant pulley
mark moves out of alignment with the pointer.
8Reconnect the vacuum pipe to the
distributor or electronic module, as
applicable, and repeat the procedure given in
the previous paragraph, when for the same
increase in engine speed, the alignment
differential between the pulley mark and
pointer should be greater than previously
observed.
9If the pulley mark does not appear to move
during the first part of the check, a fault in the
distributor mechanical advance mechanism is
indicated. No increased movement of the
mark during the second part of the check
indicates a punctured diaphragm in the
distributor vacuum unit, or a leak in the
vacuum line.
10On completion of the adjustments and
checks, stop the engine and disconnect the
timing light. Where applicable, reconnect the
vacuum pipe, if not already done, and
reconnect any “octane adjustment” and “idle
speed adjustment” wires. Make a final check
to ensure that the distributor clamp bolt is
tight.
11Finally, the idle speed and mixture should
be checked and adjusted.2.0 litre DOHC carburettor model
12The ignition timing is controlled by the
ESC II module, and no adjustment is possible.
2.0 litre DOHC fuel injection
model
13The ignition timing is controlled by the
EEC IV module, and no adjustment is
possible.
Note: Refer to the Specifications Section at
the beginning of this Chapter for ignition
timing values for use with unleaded petrol.
1To run an engine on unleaded petrol,
certain criteria must be met, and it may be
helpful to first describe the various terms used
for the different types of petrol:
Normal leaded petrol (4-star, 97 RON):
Petrol which has a low amount of lead added
during manufacture (0.15 g/litre), in addition to
the natural lead found in crude oil.
Unleaded petrol (Premium, 95 RON):
Has no lead added during manufacture, but
still has the natural lead content of crude oil.
Lead free petrol: Contains no lead. It has
no lead added during manufacture, and the
natural lead content is refined out. This
type of petrol is not currently available for
general use in the UK and should not be
confused with unleaded petrol.
2To run an engine continuously on unleaded
petrol, suitable hardened valve seat inserts
must be fitted to the cylinder head.
3The OHC engines fitted to the Sierra/P100
range which have suitable valve seat inserts
fitted at manufacture can be identified by
letters stamped on the cylinder head next to
No 4 spark plug as follows:
1.6 litre enginesM, MM, N, or NN
1.6 litre enginesS or SS
2.0 litre enginesL, P, PP, R, or RR4All CVH engines have suitable valve seat
inserts fitted.
5Vehicles which have no identification letter
stamped on the cylinder head, and are not
fitted with suitable valve seat inserts, may still
be run on unleaded petrol (although
continuous use is not recommended),
provided that every fourth tank filling is of
normal leaded petrol, ie: three tanks of
unleaded petrol followed by one tank of
normal leaded petrol.
6When running an OHC engine on unleaded
petrol (Premium, 95 RON), the ignition timing
must be retarded as described in the
following sub-Sections. There is no
requirement for ignition timing adjustment
when running CVH engines on unleaded
petrol.
Inductive discharge ignition
system and ESC system
7On vehicles fitted with an inductive
discharge ignition system, or the ESC system,
the ignition timing should be retarded as
specified.
ESC II and EEC IV systems
8On vehicles fitted with the ESC II or EEC IV
systems, there is a facility for retarding the
ignition timing without physically disturbing
the distributor.
9Adjustment is made by earthing one or two
wires (“octane adjustment” wires) which
terminate in a wiring plug next to the ignition
coil. Ideally a service adjustment lead,
available from a Ford dealer should be used
(see illustration). One end of the lead plugs
into the “octane adjustment” wiring plug, and
the other end should be earthed by fixing to
one of the ignition coil securing screws.
10Cut and insulate the wires in the service
lead which are not to be earthed.
17Ignition timing -adjustmentfor
usewithunleadedpetrol
5•18Engine electrical systems
17.9 Service adjustment lead and plug -
ESC II and EEC IV systems
A Red, blue and yellow wires
B Plug
C Wire cutting point
16.2b Crankshaft pulley timing marks - SOHC engine
A Cast pulleyB Pressed steel pulley

11The amount of ignition retardation
provided by earthing the wire(s) is as shown in
the table above.
12Once the ignition timing has been
retarded, the vehicle can be operated on
either leaded or unleaded petrol.
13On 2.0 litre models, if the yellow wire (“idle
speed adjustment” wire) in the service lead is
earthed, the idle speed will be raised by 75
rpm. If the vehicle already has a single yellow
fly lead connected prior to connecting the
service lead, ensure that the yellow wire in the
service lead is earthed.
14Note that some early models have
coloured “Lucar” connectors fitted in place of
the “octane adjustment” wiring plug (see
illustration). The principle for ignition timing
adjustment on these vehicles is as described
previously for vehicles with the “octane
adjustment” wiring plug.15On completion of ignition timing
adjustment, the idle speed and mixture should
be checked and adjusted as necessary.
Note: Refer to Section 1 for precautions to be
observed when working with electronic
modules.
1Disconnect the battery negative lead.
All ESC modules except ESC
(early “Economy” models)
2All modules except the ESC Hybrid module
are mounted on the left-hand side of the
engine compartment(see illustration).The
ESC Hybrid module is mounted on the
right-hand side of the engine compartment.
3Disconnect the module wiring plug by
pulling on the plug, not the wiring. On ESC IImodules, except those fitted to 1.8 litre
models from February 1987, a locking tab at
the lower end of the wiring plug must be
depressed before unhooking the upper end of
the plug from the module. On ESC II modules
fitted to 1.8 litre models from February 1987
(see illustration)and ESC Hybrid modules,
the wiring plug is secured by a screw which is
integral with the plug (see illustrations).
4Where applicable, disconnect the vacuum
pipe from the module (see illustration).
5Remove the two or three securing screws,
as applicable, and withdraw the module from
the engine compartment. Note that the top
securing screw of the ESC module also
secures the ignition coil strap.
6Refitting is a reversal of removal, but ensure
that the underside of the module and the
corresponding area of the body panel are clean.
ESC module (early “Economy”
models)
7Remove the module complete with its
securing bracket, as described above.
8Fit the new module, slightly behind the old
module position, on the flat vertical surface of
the body panel, and secure with the two
screws supplied. Note that the module must
be mounted against the flat area of the body
panel to prevent distortion of the module, and
to ensure good heat transfer from the module
to the body.
9Reconnect the module vacuum pipe.
10Connect the adapter loom supplied with
the new module between the module and the
old module’s wiring plug.
11Where applicable, refit the coil to its
original location.
18Electronic modules - removal
and refitting
Engine electrical systems 5•19
5
18.4 Disconnecting ESC II module vacuum
pipe18.3c Disconnecting ESC Hybrid module
wiring plug18.3b Disconnecting ESC II module wiring
plug
18.2 ESC module securing screws (arrowed)
A Wiring plug B Vacuum pipe18.3a ESC II module - 1.8 litre models from
February 1987
SystemDegrees of retardation
Blue wireRed wireBlue and red
wires
ESC II (except 1.8 litre)
models from February1987246
ESC II (1.8 litre models from
February 1987)426
EEC IV42617.14 Lucar type “octane
adjustment” connectors -
early models with ESC II
and EEC IV systems
A Red, blue and yellow connectors
B Coil securing screw (earthing point)