How can i test car ignition coil.(by colour of spark)

Felicia97 carburater

Thanks

Edited 23 April, 20188 yr by Romanyshawky

First you need to do a basic resistance test by using a multimeter. The primary coil (between pin 1 and 15) should measure 1 - 2 Ohms. The secondary coil (between pin 1 and central terminal) should measure around 10 kOhms.

 

Now, the basic resistance test is not a definitive test because we've tested the coils using very low voltage and current (from the battery of the multimeter) while in a car the primary coil runs up to a few hundred volts and the secondary coil delivers tens of kiloVolts. High voltage can break the insulation between the turns of the coil resulting in lower high voltage and heat felt by touching its housing.

 

As for the health of the coil by observing the colour of the spark while the engine is running, there are a few things to clear first.

1. It is not important the colour of the spark but the air gap that the spark can cross. We measure the high voltage by using a spark plug tester like the one in the video below. The spark should be consistent, not random.
2. When the coil output is weak, the spark is yellow/red and thin. When the coil output is strong, the spark is blue/purple/white and fat. 

 

 

@RicardoM  Brilliant thoroughly informative detailed answers as always, Respect.

18 hours ago, RicardoM said:

First you need to do a basic resistance test by using a multimeter. The primary coil (between pin 1 and 15) should measure 1 - 2 Ohms. The secondary coil (between pin 1 and central terminal) should measure around 10 kOhms.

 

Now, the basic resistance test is not a definitive test because we've tested the coils using very low voltage and current (from the battery of the multimeter) while in a car the primary coil runs up to a few hundred volts and the secondary coil delivers tens of kiloVolts. High voltage can break the insulation between the turns of the coil resulting in lower high voltage and heat felt by touching its housing.

 

As for the health of the coil by observing the colour of the spark while the engine is running, there are a few things to clear first.

1. It is not important the colour of the spark but the air gap that the spark can cross. We measure the high voltage by using a spark plug tester like the one in the video below. The spark should be consistent, not random.
2. When the coil output is weak, the spark is yellow/red and thin. When the coil output is strong, the spark is blue/purple/white and fat. 

 

 

Thank you Ricardo.....i will buy multimeter to measure resistance but i tried the out put  and found  the spark is yellow and thin but  consistent, not random.so what is your opinion?

As I've said, use a spark gap tester and see how many kilovolts has the output of ignition coil. I can't decide only based on the colour of the spark. Let's not forget that the primary of the coil gets voltage from the electronic ignition. If there is not enough voltage in the primary, the output of the coil will be low.

 

Here are some testers.

The video below shows another ignition coil tester. I'd say it is easy to replicate.

 

@Romanyshawky - What @RicardoM says about the power of the spark between the plug electrodes being nothing to do with the colour of the arc is correct.

 

Are you using a "window plug" such as Gunson's Colourtune (UK product) to determine the colour? If so, then you're actually looking at the colour of the flame front in an ignited fuel mixture and not the colour of the electric arc anyway?