Ok I think things were being misinterpreted. My apologies, because its probably my fault.
Currently how the tach was/is wired up was like you just said. Red to power. Black to ground. Yellow to light. Green to negative terminal on coil.
When it is wired like that though it is causing the coil to fire when the key is in the on position before crankiit over. After taking the green wire off the negative terminal of the coil, the ignition coil no longer starts to fire before cranking the engine over.
