need help to figure out starting problem on my car

i have a 1966 Pontiac Parisienne , it has been converted to a chev 350 with throttle body injection, my car was running fine and somehow i knocked a wire out from somewhere, my issue now is when turning the key to start the car , nothing happens, but if i take this wire that is just laying there and touch the negative terminal as i turn the key, the engine starts fine, i can let go of the wire and engine stays running.. i have tried connecting this wire to the negative battery terminal and then turning the key and nothing happens, car will not start, it will only start when i turn the key to crank the engine and then have someone touch the wire to negative terminal..Any help would be much appreciated if someone knows where this wire belongs...thanks in advance..