[Flathead Fever]

Everybody needs a digital voltmeter. The very first thing to check is the available voltage to the coil with the key on and points open if it uses points. If the points are closed it will read zero. Then like others have said you need to know if your coil has an internal resister or requires and external one. You don't want them both or it will cutdown your voltage too much and you will have a weak spark. You can try another condenser and those are rated to match the coil. You want to use the condenser with the same capacitance that was originally used with whichever coil you are using. They are a matched set. Make sure you don't have the polarity on the coil reversed. Make sure it's a coil made for positive or negative ground and 12V or 6V depending on what you have. Check the coil wire spark compared to a plug wire spark.

If its electronic ignition you want to use a special "test spark plug". All the auto parts stores have them. What can happen if you do not use the test plug is when you hold just the spark plug wire away from a ground, the coil will try to build up whatever voltage it takes to jump the gap. If you're holding it too far for the spark to jump the coil will build up a large voltage that will look for another path to ground and it can backtrack trough the electronic ignition module and damage it. I was master mechanic for 30-years and the manuals warned against checking for spark on electronic ignitions without using a test plug. It can burn a microscopic hole in a transistor that over time cane fail. It won't do it right away. A couple years later your ignition module could fail, and you won't realize it was from when you tested for spark a long time ago. Better safe than sorry.