Traditional Ignition - Tecnotest 138-E Bedienungsanleitung

TIMING LIGHT ___________________________________________________________________________
1.2 -

Traditional ignition

In the traditional ignition the electrical power absorbed from the battery (32) is
supplied to the coil primary winding (30) through the ignition switch (27).
The coil stores
contact points (23).
If the distributor works correctly, when the timer rotor arm (21) while rotating reaches
the position of the electrode of one of the plug, the cam (22) makes the
contact points (23) open.
As soon as points (23) open, the power drops to zero and due to the well-known
phenomena of the electromagnetic induction a high voltage is induced into the
secondary winding (29) and conveyed to the timer rotor arm (21) at a value making
the spark fire between the electrode of the arm and the electrode of the plug.
Despite its efficacy, the disadvantage of this system is the possibility of an excessive
wear of points undergoing a continuos power passage.
It is advisable to check the points dwell (DWELL) periodically to know whether between
two subsequent sparks the points remain closed for a correct period (expressed in
degrees) with regard to the cam rotation.
The example shown (picture b) resumes the functioning of a 4-cylinder engine
(4 spark plugs) whose ignition cycle is: 1° - 3° - 4° - 2° cylinder.
The picture b shows the ignition system at the spark firing on the 2° cylinder.
19. Upper part of the distributor (Cap)
20. Lower part of the distributor
21. Timer rotor arm
22. Cam
23. Points
24. High voltage
25. Capacitor
As it might be noticed, the cam (22) is pushing to the outside the rotor arm to which
the point (23) is connected thus opening the contact.
In this way the high voltage is obtained which, through the wire (22), reaches the
timer rotor arm (21) just while the rotating electrode perfectly corresponds to the
2° cylinder plug wire electrode.
The closeness of the two electrodes triggers the spark which starts the ignition.
The cycle repeats 3 more times and, namely, when the timer rotor arm meets the
electrodes of the remaining plugs which, as it might be noticed, are located according
to the cylinders ignition sequence 1 - 3 - 4 - 2.
30
power and the battery voltage
26. Spark plugs
27. Ignition switch
28. Coil primary signal
29. Secondary winding
30. Primary winding
31. Coil
32. Battery
(12 Volts) reaches
SERVICE MANUAL
the