wont start 1991 626
 

I am having a little trouble diagnosing a problem and need some assistance. The engine cranks but won't start, the tach jumps while I am cranking so I am assuming the igniter is good. I pulled the coil off to change it but wanted to make sure it was bad before I bought a new one. I plugged 12v into the positive side and put a ground wire on the negative I put a timing light on the wire and interupted the negative side of the coil to act as a set of points the coil fired a thin blue spark like it was fine. I had my timing light on the coil wire and it did not light. my question is can the the coil be weak enough to throw a spark and not fire the cylinder or my light? The light is fine I hooked it to another car and it worked nomal.
thanks
Ben