Need help checking spark

[aussieflash]

Can anyone help with the correct and safe way to check spark for myself and my motor.Also do I need any special tools.
1988 V6 Merc.Thanks.

 

[aussieflash]

Re: Need help checking spark

So just pull plug and put against engine block and crank.Do I pull all plugs or 1 at a time?Also do I touch plug on engine or leave a gap.Thanks.

 

[Raystownboater]

Re: Need help checking spark

You can just pull 1 plug and rest it against the block (or manifold). If you have a small gap, the spark will jump, making it easier to see.

 

[Moody Blue]

Re: Need help checking spark

You can enlist the help of an unsuspecting assistant. Have them grab hold of the sparkplug body with one hand and the place the other hand on the engine housing. Crank the engine over and see how high you assistant jumps. Little tingle = poor spark. Both feet off the ground = good spark.

Seriously, you should pull all plugs and ground them on the engine away from the plug holes. If you just pull one plug and have it grounded near the plug hole, it is possible that the motor could start creating quite an exciting fireworks display at the open plug hole.

Another way to check is with an in-line spark tester. Leave all the plugs installed, pull one plug wire and connect the tester between the plug wire and plug. Crank over or start the engine. The spark will be visible in the spark tester.

 

[j_martin]

Re: Need help checking spark

A weak spark may easily jump the plug gap outside the cylinder, but fail to fire the plug when it's installed. That's because increased pressure causes an increase in the voltage required to jump the gap.

This tool, set up for 7/16" gaps, is the best bet for checking the spark of your engine.

 

[aussieflash]

Re: Need help checking spark

Thanks for your help.