How do I test each individal plug for spark? I think I fouled a few.

 

Edit: my thread title is misleading-question about the old plugs and testing them.

 

There are spark plug testers. It uses a light to see the spark. A more accurate reading would be to use an oscilloscope. That can determine spark timing, spark length, or if it's getting spark of individual cylinders. Might be expensive and a shop would have to do it, but it depends on what exactly you want to know.

 

Pull them out, put one by one in on the #1 Wire, have someone turn the key to start the car for a couple of revolutions and you hold the Plug next to the Header to see if it sparks.