How to check for spark

[steph]

Newby here and thanks in advance. This forum is really great and filled with lots of usefull info and tricks. Save time and lots of $$$

My question, what is the best way to check if the spark plug is actually firing?

 

[fireman57]

Re: How to check for spark

I think the real question is are you getting proper spark to the plug. You need a bright blue spark to fire your plug. If it is yellow or orange it is too weak to do the job. If you have good spark to the plug the only way I know to check to see if the plug is actually firing would be to swap plugs or put in a new one.

 

[steph]

Re: How to check for spark

Thanks fireman57 but how do I check to see if the spark is bright blue, yellow or orange?

 

[steph]

Re: How to check for spark

If I remove the spark plug from the block but leave it on the spark plug cable and crack the engine should there be a spark or does the spark plug have to be grouded to the block?

 

[ezeke]

Re: How to check for spark

It would have to be grounded.

The way to test on cd ignitions is with all plugs out. If you want to see if the spark is adequate you need a tester.

 

[F_R]

Re: How to check for spark

Checking for spark across the plug gap is a nearly worthless test. It has to be able to fire a much wider gap than that outside the cylinder. That's because it take more voltage to fire the plug installed and under compression.

Typical spark gaps are 1/4" for magnetos to 7/16" for CD ignitions. There are commercial spark checkers available, but there is nothing like the satisfaction of inventing your own. What is required is a couple of sharp pointed metal pins, one grounded and one to connect to the plug wire. Multiply by the number of cylinders in your motor. Now, let's see what you come up with. Here's one I made from a busted boat windshield 50 years ago and still use it.