IGNITION
I
gn
iti o n The ignition timing is set dynamically to give optimum engine performance with
timing
efficient engine emission c
ontro
l. Electronic test equipment must be used to
check the ignition timing setting and the aut
oma
tic advance (see 'GENERAL
DATA'). Checking and adjustment to the ignition timing setting should be
carried out by your Austin MG Dealer control service station.
The dynamic ignition timing must be checked after cleaning, resetting, or renew-
ing of the distributo r contacts. '\
Basic tuning data will be f
ound
on the Vehicle Emission Control
Inf
orma
tion
Label located in the engine compartment. .
Distri
butor
Cleaning contacts. Inspect the contact points (1) and, if burned, clean with fine
Fig. 1 emery cloth or fine carb
orun
dum stone. Wipe the contacts clean with a fuel-
moistened cloth. Renew pitted or w
orn
points. .
Fitting. Before fitting a new contact set, wipe the points clean with fuel or spirit.
Lubricate the pivot post (2)
and
check that the insulating bush (9) is correctly
positioned below the spring loop. Position the contact set on the distributor
plate and lightly tighten the securing screw
(6)
~
Locate the lead terminals
around
the insulating bush so
that
they make contact with the spring and tighten the
nut
(8). Set the contact gap.
Whenever a new contact set has been fitted, recheck the gap after the first 500
miles (800 km.).
Dur
ing this period, the heel of the contact will have bedded in
and reduced the gap.
Ignition
cables
'The high-tension cables connecting the distributor to the sparking plugs may,
(high-tension)
after long use, also show signs of perishing; They must then be replaced by the
correct type of ignition cable.
Lubrication. Very lightly smear the pivot post (2) and aro und the cam (3) with
grease. Add a few drops of oil through the hole in the contact breaker plate to
lubricate the centrifugal weights and
around
the screw (5) in the centre of the
cam spindle (do
not
remove this screw' as clearance is provided for oil to pass).
Avoid over-lubricating. Carefully wipe away all surplus lubricant and see that the
contact breaker points are perfectly clean and dry.
Contact breaker gap. Turn the crankshaft until the points are fully open. Check
the contact gap
(1) with a feeler gauge (see 'GENERAL DATA') ; the gauge
should be a sliding fit in the gap.
If
the gap varies appreciably from the gauge thickness, slacken the contact plate
securing screw (6) and adjust the gap by inserting a screwdriver in the notched
hole (7) at the end of the plate and turning clockwise to decrease and anti-
clockwise to increase the gap. Tighten the securing screw. Turn the crankshaft
and recheck the gap. Refit the rotor, wipe the inside of the distributor cover
clean
and
refit.
Contact set renewing. Removing. Remove the nut (8), lift the top insulating bush
and
both
leads from the stud. Remove the securing screw (6) with its spring and
plain washers, and lift off the one-piece contact set. If removal of the moving
contact
onl y is required, leave the securing screw (6) in position.
The dynamic ignition timing must be checked after cleaning, resetting, or renew-
ing of the distributor contacts. '\
Basic tuning data will be found on the Vehicle Emission Control Information
Label located in the engine compartment. .
Spark
plugs
Fig. 2
I~EI
~~~
,~
The spark plugs should be cleaned, preferably with an air-blast service unit.
Check the plug gaps, and reset if necessary to the recommended gap (see
'GENERAL DATA'). To reset, use a special Champion spark plug gauge and
setting tool; move the side electrode, never the centre one.
When refitting the plugs make sure
that
the washers are not defective in any way.
Screw the plug down by hand as far as possible, then use a spanner for tightening
only. Always use a tubular box spanner to avoid possible damage to the insulator,
and do not under any circumstances use a movable wrench. Never overtighten a
plug,
but
ensure that a good joint is.made between the plug body, washer, and
cylinder head. Wipe clean the outside of the plugs before reconnecting the H.T.
leads. .
When fitting new spark plugs ensure
that
only the recommended type and
grade are used (see 'GENERAL DATA').
Fig. 2
Whenever a new contact set has been fitted, recheck the gap after the first 500
miles (800 km.).
Dur
ing this period, the heel of the contact will have bedded in
and reduced the gap.
Distributor
Cleaning contacts. Inspect the contact points (1) and, if burned, clean with fine
Fig. 1 emery cloth or fine carborundum stone. Wipe the contacts clean with a fuel-
moistened cloth. Renew pitted or w
orn
points. .
Lubrication. Very lightly smear the pivot post (2) and aro und the cam (3) with
grease. Add a few drops of oil through the hole in the contact breaker plate to
Ignition
cables
'The high-tension cables connecting the distributor to the sparking plugs may,
(high-tension)
after long use, also show signs of perishing; They must then be replaced by the
correct type of ignition cable.
Spark
nluus
The spark plugs should be cleaned, preferably with an air-blast service unit.
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