Auto Mechanical Work Paper 2, May/June 2014  
Questions: 1 2 3 4 5   Main
General Comments
Question 3

(3)       (a)       List four components in the primary circuit of the ignition system.
            (b)       Explain how a high voltage is induced in the secondary winding of the
                        ignition coil.
            (c)        Explain why some ignition coils are filled with oil.
            (d)       Name one component in the ignition system that can cause backfiring.
            (e)       State two effects of too small contact breaker gap.



         This question was very difficult for the candidates who attempted it as they could not provide the required responses to the various parts of the question.  The required responses to the various parts of the question are given below:

(a)       -           battery;
            -           ignition switch/switch;
            -           primary winding of ignition coil;
            -           contact breaker or contact breaker points;
            -           primary circuit wire/cable.

(b)       When the ignition is on and the contact breaker points are closed, the battery current flows through the primary winding to earth thus creating a magnetic field around iron core.

(c)        -           give greater heat dissipation,
            -           protect the coil against moisture which usually causes coil failure;
            -           ensure better insulation thus prolonging the utility life of the coil;
            -           reduce corona (glow of light) effect.

(d)       -           defective condenser;
            -           defective contact breaker;
            -           defective spark plug;
            -           defective rotor..

(e)       -           over-saturated coil at low engine speed;
            -           retarded timing of spark;
            -           overloaded condenser;
            -           misfiring;
            -           loss of power.

Powered by Sidmach Technologies(Nigeria) Limited .
Copyright © 2015 The West African Examinations Council. All rights reserved.