Weird.... only a few sparks

[E30M30]

I've got a problem with my 455 pontiac. It uses a point trigger distributor and a msd 6al - blaster 2 coil. My problem is that when I try to start the engine, it "tries" to start. I pulled a spark plug wire, and noticed the my control-plug only made 2-3 sparks and then nothing, even though I kept running the startermotor. Why does the spark "go away" any tips ???