Auto Electrical Works Paper 2, WASSCE (SC), 2021

Question 3

 

  • List two methods of controlling ignition timing.
    (b)        Briefly describe the operation of contact breakers in ignition systems.
    (c)        Fig. 1 is a schematic layout of coil ignition system of a four-cylinder engine arrangement.

    Name the parts labelled A, B, C, D, E, F, G and H.

Observation

     The expected responses were:

 

  •          Methods of controlling ignition timing
  • Advancing the ignition
  • Retarding the ignition                                                                                                      
  •       Operation of contact breaker in ignition systems
  • When the ignition switch is turned ON, current flows from the primary windings of the coil to contact breaker points.
  • Cranking of the engine in turn causes rotation of the cam lobe in the distributor.
  • The rotation of cam lobes in turn causes opening and closing of the contact breaker gap.
  • When the contact breaker is opened, current flows in the primary circuit breaks thus the current is returned into the secondary windings of the coil.
  • The secondary windings of the coil increased greatly into value high enough to cause spark at the spark plugs. 
  •  Parts of a coil ignition system

            A – Earth                                
B – Battery                             
C – Switch                             
D – Coil                                             
E – Contact breaker               
F – Capacitor/condenser                    
G – Spark plugs                                 
H – Distributor cap                

Question 3 required candidates to show a level of understanding of the ignition system. The Chief Examiner reported that while only a few candidates responded well first two tasks, majority of majority of the candidates that attempted question correctly named the parts labelled in the last task.