Get a spark plug to spark with DC
Make sure there isn't any extra or unexpected electronics involved in this spark coil (or if there is, use it to your favor). 

Regular coil



A straight-up coil is nothing more than a transformer.  The high voltage secondary has thousands of windings, and goes between the spark plug coil terminal and the chassis, because spark plug return is through the engine block. 

The low voltage primary is 12V and connects either to 2 terminals (hopefully) or to one terminal and chassis (because chassis return is how we roll in automotive electrical).  In the latter case, you cannot isolate your driver circuit from the spark voltage loop. 

You have to switch the current to the primary loop.   This is a lot of current, but it also has a pretty enormous inductive kick when you interrupt it.   You better be prepared for that! 

The spark plug fires when the magnetic field changes. I.E. When you initially connect 12V power, and again when you interrupt power.  While you are providing power, nothing happens but wasting power and making the coil hot.  

Coils with onboard switching

Now that car engines have computers, not surprisingly, engine makers do not want the computer module switching big fat coil current or dealing with kickback.  So some coils nowadays handle the heavy switching right on the coil module.  They accept 12V and also a signal input from the computer in the normal voltage ranges. 

However, they usually don't stop there.  They also add a bunch of other stuff that either gets in your way, or that you need to spend time learning.  So this type of relay may be a lost cause unless you really know what you're doing and are willing to spend the time learning. 

The classic Ford Model T syle (Pontiac Coil etc.)



The old Model T coil is a unique hybrid.  It is a combination of a spark coil and a relay, with the relay coil being the spark coil.  The 12V side of the coil is wired through the NC (normally closed) side of the relay contact.  

When the coil energizes, it opens the relay contact and de-energizes itself.  Then the coil de-energizes and the relay contact closes again, repeating the process.  They call it a "buzz box".  And you get 2 sparks every cycle, a continuous rain of sparks.  

The Buzz-box is great when you just want it to be a button.  However the buzz-box has the same amount of inductive kick as a regular coil (i.e. A lot), so whatever you drive it with had better be ready for that. I can't say how many hours I've spent with a small file fixing arc damage on the distributor contact that drives the buzz-box.  Likewise the contact on the buzz-box proper. There's nowhere to file on a MOSFET! 

the buzz-box doesn't care about polarity, so you can wire it positive or negative common, if your spark coil is wired to common.  Some are isolated, as in the photo above.  

I wish someone would make an electronic version of the buzz-box.  It would be a godsend for old-engine people who are sick of filing points. Pontiac Coil left the business in the early 00s after the employees putting the labor-of-love into the gorgeous tongue-and-groove wood boxes retired.  I hear others have restarted production.