Starter Grounding Question

[xludan]

I am in the process of rewiring my truck and I can't remember if there was a wire grounding the starter or not. I currently have the starter hooked up as follows:

-Wire from positive battery terminal to big post
-Purple wire to the 's' terminal
-yellow wire to the 'r' terminal

My problem is when I turn the ignition key nothing happens at all. I found that if i take a jumper wire from the negative battery terminal to the housing of the starter the starter engadges and works just fine. So am I missing a ground wire somewhere?