anyone help me on a piece of elec problem?

hey guys,,, need little piece of advice from the eiec dept... i dropped a 440 in a street rod and tried to start it today,, it turns good but wont start until I let go of the ign switch.. then it fires up,,if i hold ithe switch in the start position, it wont start, if I direct 12v to the resister, she fires right up,,, sounds like I need 12v runing someplace while the engine is turning over;;; can anyone shed some light for me..... thanks in advance...

christineman