How bright should the spark be if you hold the boot away from the plug to check for a spark?

Better yet, how can you check for a weak spark?

Scott

 

Pull a spark plug, hook up the wire, and hold the plug against the head while cranking. It should be about as wide as the center electrode, white or blush white, and audable if i remember.

Also, careful you dont get shocked. It hurts...

 

A better idea would be to use a spark tester.

 

Good spark= blusih white
Bad spark = red-orange

 

Be carefull with aftermarket ingnition boxes thou. Ive seen some that will be red at lower rpms and white at higher rpms. While the red at lower rpms may seem bad its actually operating just fine.

 

No aftermarket box here.

I've had this problem before and it was the distributer. I wonder if it was replaced waith a cruddy rebuilt one and it's going south again.

Anyway of testing the distributer without taking it out?

 

Theres really no test for it. Its just a visual on the cap and rotor.

 

Actually, I was thinking more along the lines of the electronics.

Do you have to pull the distributer to check the module or can it be done in car?

Thanks

 

No, and no.

Easiest way is to take it out, take it to a parts store that has a tester, and get them to do it.

Why would you want to check for "weak spark" in the first place?

 

Actually, it was for a possble no spark situation.

A few years ago, my car just died. It would crank but wouldn't start and since I was near a pep boys, I pushed it there.

They told me it was my distributer and replaced it.

It happened again the other day. It wouldn't start and when I checked for a spark, it looked pretty small and weak. The car then started but as I was driving, it cut out. It started up again and I made it home but I wan't to test the ignition system before I drive it anywhere else.

 

Sounds like the ignition module might be over heating and crapping out.

 

Use a GM module and accept no substitute. Also remember to clean the mounting surface and use plenty of heat sinking grease when installing a new module.

 

Why no sub? Have you had or have first hand knowledge of anyone haveing a problem with a quality aftermarket module from Accel or Pertronix? Please explain your statement on no substitute.

Goes without saying about the cleaning and use of thermal compound ("grease"). The best heatsink compound is called Artic Silver and it's available from the computer nerd/geek suppliers. It has much higher thermal conductivity than the normal stuff.

 

The "aftermarket" modules have been notorious for failing in a very short time. And the "high dollar" ones from pertonix, mallory etc. are no better than a factory GM module, they just cost more.