Ignition System - Testing; Contact Breaker Points - Gap And Dwell Angle Adjustment; Engine Fails To Start; Engine Misfires - Opel Kadett Owner's Manual

5B•2 Contact breaker ignition system

2 Ignition system - testing

1 By far the majority of breakdown and
running troubles are caused by faults in the
ignition system either in the low tension or
high tension circuits.
2 There are two main symptoms indicating
faults. Either the engine will not start or fire, or
the engine is difficult to start and misfires. If it
is a regular misfire, (ie the engine is running on
only two or three cylinders), the fault is almost
sure to be in the secondary or high tension
circuit. If the misfiring is intermittent the fault
could be in either the high or low tension
circuits. If the car stops suddenly, or will not
start at all, it is likely that the fault is in the low
tension circuit. Loss of
overheating, apart from faulty carburation
settings, are normally due to faults in the
distributor or to incorrect ignition timing.

Engine fails to start

3 If the engine fails to start and the car was
running normally when it was last used, first
check that there is fuel in the petrol tank. If the
engine turns over normally on the starter
motor and the battery is evidently well
charged, then the fault may be in either the
high or low tension circuits. First check the HT
circuit.
4 One of the commonest reasons for bad
starting is wet or damp spark plug leads and
distributor. Remove the distributor cap. If
condensation is visible internally dry the cap
with a rag and also wipe over the leads. Refit
the cap. If the engine fails to start due to either
damp HT leads or distributor cap, a moisture
dispersant can be very effective. To prevent
the problem recurring, a proprietry damp start
product can be used to provide a sealing
coat, so excluding any further moisture from
the ignition system. In extreme difficulty, a
proprietry cold start product will help to start a
car when only a very poor spark occurs.
5 If the engine still fails to start, check that
voltage is reaching the plugs by disconnecting
each plug lead in turn at the spark plug end,
and holding the end of the cable with rubber or
an insulated tool about 6 mm away from the
cylinder block. Spin the engine on the starter
motor. Note Do not operate the starter system
with the plug leads disconnected in any other
way to that described, or damage to system
components may result.
6 Sparking between the end of the cable and
the block should be fairly strong with a regular
blue spark. If voltage is reaching the plugs,
then remove them and clean and regap them.
The engine should now start.
7 If there is no spark at the plug leads, take
off the HT lead from the centre of the
distributor cap and hold it to the block as
before. Spin the engine on the starter once
more. A rapid succession of blue sparks
between the end of the lead and the block
indicates that the coil is in order and that the
distributor cap is cracked, the rotor arm is
faulty or the carbon brush in the top of the
distributor cap is not making good contact
with the spring on the rotor arm.
8 If there are no sparks from the end of the
lead from the coil, check the connections at
the coil end of the lead. If it is in order start
checking the low tension circuit. Possibly, the
points are in bad condition. Clean and reset
them as described in this Chapter, Section 3.
9 Use a 12V voltmeter or a 12V bulb and two
lengths of wire. With the ignition switched on
and the points open, test between the low
tension wire to the coil and earth. No reading
indicates a break in the supply from the
ignition switch. Check the connections at the
switch to see if any are loose. Refit them and
the engine should run. A reading shows a
faulty coil or condenser, or broken lead
power and
between the coil and the distributor.
10 Take the condenser wire off the points
assembly and with the points open test
between the moving point and earth. If there
is now a reading then the fault is in the
condenser. Fit a new one and the fault is
cleared.
11 With no reading from the moving point to
earth, take a reading between earth and the
distributor terminal of the coil A reading here
shows a broken wire which will need to be
replaced between the coil and the distributor.
No reading confirms that the coil has failed
and must be renewed, after which the engine
will run once more. Remember to refit the
condenser wire to the points assembly. For
these tests it is sufficient to separate the
points with a piece of dry paper while testing
with the points open.

Engine misfires

12 If the engine misfires regularly, run it at a
fast idling speed. Pull off each of the plug
caps in turn and listen to the note of the
engine. Hold the plug cap in a dry cloth or
with a rubber glove as additional protection
against a shock from the HT supply.
13 No difference in engine running will be
noticed when the lead from the defective
circuit is removed. Removing the lead from
one of the good cylinders will accentuate the
misfire.
14 Remove the plug lead from the plug which
is not firing and hold it about 6 mm away from
the block. Restart the engine. If the sparking is
fairly strong and regular, the fault must lie in
the spark plug.
15 The plug may be loose, the insulation may
be cracked, or the points may have burnt
away giving too wide a gap for the spark to
jump. Worse still, one of the points may have
broken off. Either renew the plug, or clean it,
reset the gap, and then test it.
16 If there is no spark at the end of the plug
lead, or if it is weak and intermittent, check
the ignition lead from the distributor to the
plug. If the insulation is cracked or perished,
renew the lead. Check the connections at the
distributor cap.
17 If there is still no spark, examine the
distributor cap carefully for tracking. This can
be recognised by a very thin black line running
between two or more electrodes, or between
an electrode and some other part of the
distributor. These lines are paths which now
conduct electricity across the cap thus letting
it run to earth. The only answer is a new
distributor cap.
18 Apart from the ignition timing being
incorrect, other causes of misfiring have
already been dealt with under the Selection
dealing with the failure of the engine to start.
To recap, these are that:
a) The coil may be faulty giving an
intermittent misfire.
b) There may be a damaged wire or loose
connection in the low tension circuit.
c) The condenser may be faulty.
d) There may be a mechanical fault in the
distributor (broken driving spindle or
contact breaker spring).
19 If the ignition timing is too far retarded, it
should be noted that the engine will tend to
overheat, and there will be a quite noticeable
drop in power. If the engine is overheating and
the power is down, and the ignition timing is
correct, then the carburettor should be
checked, as it is likely that this is where the
fault lies.
3 Contact breaker points - gap
and dwell angle adjustment
1 To adjust the contact breaker points so that
the correct gap is obtained, first undo the two
distributor cap retaining screws, lift off the
cap and withdraw the rotor arm from the
distributor shaft. At this stage it is a good idea
to clean the inside and outside of the cap and
inspect its condition. It is unlikely that the four
segments inside the cap will be badly burned
or corroded, but if they are the cap must be
renewed. If only a small deposit is on the
segments, it may be scraped away using a
small screwdriver.
2 Push in the carbon brush located in the
centre of the cap several times to ensure that
it moves freely. The brush should protrude by
at least 6 mm.
3 Gently prise the contact breaker points
open to examine the condition of their faces. If
they are rough, pitted or dirty it will be
necessary to remove them to enable new
points to be fitted.
4 Assuming that the points are in a
satisfactory condition, or that they have been
renewed, the gap between the two faces
should be measured using feeler blades as
follows.
5 Pull off the plug leads, after marking them
to ensure correct refitment, and then remove
the spark plugs.
6 With the transmission in gear and the
handbrake released, slowly pull the car
forward, while at the same time watching the
distributor, until the heel of the contact