1966 dodge charger 383 4speed

mopar electronic ignition

I installed my msd atmoic and first few intial drives it worked great. Yesterday i had problems getting it to start, when it was cranking i noticed it wasnt showing any rpm on the hand held controller. I think i remeber seeing it was showing 150-200 rpms when it would fire up. Do i need to get a tach signal gmr pickup so it can get a better low rpm read so the injectors can fire?