You probably know that
the spark does not arc between the spark plug electrodes right at the instant
when the piston is at top dead center (TDC), but a bit earlier. Exact point
of the generating of the spark we'll call ignition point, and angle made by
crankshaft between ignition point and TDC is ignition advance angle.
The value of the advance angle has a great influence to the proper work of the
engine. For example horsepower output, fuel consumption, but also temperature
level and pressure in cylinder, and therefore greasing effects, and finally
lifetime of the engine are the parameters depending on this value. Inappropriate
value of this angle may also cause "knocking" - improper combustion
process in the forms of detonations and preignition, which can lead to the engine
damage.
Optimal values for the advance angle depend on the revolution speed and external
load. Centrifugal ignition control unit provides advance regulation as the function
of the revolution speed. The component that can regulate angle of advance as
the function of external load, vacuum ignition control unit, is not installed
on Citroen 'A'-series models.
The main parts of the ignition system are the coil and the contact points (or
breaker, if you prefer). The spark is generated at the instant of separating
of the points, therefore that's what determines the ignition point. Since the
contact points contain movable parts, the wear and deformations are caused in
exploitation of the engine, as well as burning of points' surfaces due to very
high voltage. As result, the advance angle is changed so it has to be adjusted
to its proper value.
Ignition point should be checked at least once a year or after car covers 5,000
km.
Checking
ignition point
there are two control
holes - one of them is on the housing, and the other one is on the flywheel.
These holes must be toward each other at the instant of separating of the
contact points
for this checking you'll
need control lamp and 5 mm diameter rod - 150 mm long
first step is to find
the control hole on the left hand side of the housing (use figure 1
to make it easier) and to push the rod through it; note - this hole is a bit
under the manifold, don't mix it with upper one
Figure 1:two control holes (1-housing, 2-flywheel)
turn the flywheel slowly
(use the starting handle for greater displacement or push its teeth with the
screwdriver for the fine position adjustment) until you find the control hole
on it (see figure 1)
remove the lead from
the coil which leads to the points and overcome interrupted primary
electrical circuit with the control lamp (see figure 2)
Note:
this way we made serial connection of the control lamp into the primary
circuit. It could also be connected in parallel. In this second case
light should be "on" when points are separated and vice versa
(see below). This way is described in most manuals.
Figure 2: 1-control lamp, 2-points power lead, 3-coil power lead
turn the contact on:
if control holes are not approximately in position toward each other, the
control lamp should give light (points are still connected and primary electrical
circuit is closed)
keep turning the flywheel
exactly to the position by which the control lamp come off (which means points
have just been separated from each other) and let it remain still; in this
moment control holes are approximately toward each other (or at least they
should be until everything is more or less all right with your engine)
push the rod through
the hole in the housing toward the hole in the flywheel
if the rod goes right
through the hole in the flywheel, advance angle is perfect; according to factory
manual, you can tolerate disagreement up to 1 degree (2/3 width of one flywheel's
tooth). Otherwise, notice whether the contact points separated from each other
before (early spark - too big advance angle) or after (late spark
- to small advance angle) the holes came toward each other
turn the flywheel for
360 degrees so that you can repeat the procedure for other cylinder; according
to factory manual, maximum allowed disagreement between two cylinders is 3
degrees (width of one tooth and one space between teeth measured together)
if the checking shows
the proper value for the advance angle (between the limits of tolerated disagreement),
put all parts in their places and don't forget to remove control rod from
the flywheel and housing before starting the engine!
Adjusting
ignition point
remove sheet panel with
a grille between front wings (Dyane and Ami) and protecting wire net in front
of the fan
unbolt and remove the
rubber cover in front of the point box, which is located under the endpoint
of the crankshaft
unscrew three bolts
and remove the points box cover
check the contact points
visually: if their surfaces are too uneven and deformed, the points should
be replaced. Instructions for replacing contacts is not included here by now,
but here is appropriate scheme
which can be helpful
next thing is to check
the gap between the points (breaker gap) (see figure 3): turn the flywheel
slowly until the points (position 5) reach the maximum distance between each
other; then insert feeler gauges between their surfaces. Value of the gap
must be 0.4 mm (+/- 0.05 mm)
if necessary, adjust
the gap: unscrew the retaining bolt (position 7) and change the position of
the fixed breaker element (position 6) until the gap is adjusted properly;
tighten the retaining bolt
measure the gap again;
repeat adjusting if necessary
Figure 3: parts of the breaker
now adjust ignition
point (figure 4): turn the flywheel until the control holes are right
toward each other again; fix the position of the flywheel with the rod; loosen
points box retaining bolts (position 1) so that you can turn the points box
in order to ô \ÜÎ^
Do
It Yourself
