Observation

     

      

1. Ignition timing
• The process of setting the angle relative to position of piston and crankshaft angular velocity that will cause a spark to occur in the combustion chamber near the end of the compression stroke.                                                                                              


• This refers to timing the rotor to the corresponding position of the crankshaft angle to enable the occurrence of spark in the combustion chambers in the correct sequence.


• The process of setting the time that a spark will occur in the time that a spark will occur in the combustion chamber relative to piston position.                                


• The ignition timing sets the right point at which the air-fuel mixture in the engine combustion chamber is ignited.


• The arrangement of plug wire in firing order and the settings on distributions of the ignition system to ensure sparks occurs at the right time and correct sequence.



 

 

                                                                                                                                   
   

2.      Symptoms of incorrect ignition timing in a motor vehicle


• Poor fuel economy


• Sluggish acceleration


• Hard starting


• Back firing/Missfiring


• Pinging


• Spark knock


• Overheating


• Incomplete combustion


• Poor engine speed/acceleration


3. Table 3





	Fault	Effect on ignition system
	Cracked distributor cover	Hard starting Jerking Loss of power
	Worn out distributor cover segment	Current leakage Engine failing to start Misfiring Difficulty in climbing hill Uneven engine sound

                                                                                                                                               
  

4.      
        
   1.   Function of capacitor in ignition system
   
   
   • Prevents arcing/ burning at the contact breaker points.
   
   
   • Absorbs excess current that tends to jump the gap.
   
   
   • To store electrical energy and give it out when needed.
   
   

                             

   2.      Function of distributor in ignition system
   
   To route/distribute secondary/high voltage/current from the ignition coil to the spark
   plugs in the correct firing order and for correct amount of time.                  
   
   

   The Chief Examiner reported that majority of the candidates that attempted question 2 responded very satisfactorily.