No spark

I have a 94 aerostar that wont start. It had an intermittent starting issue before I replaced the wires, plugs, rotor, and cap, then there was no spark... so I replaced the ignition coil, still no spark, but when I cranked it over with the wire off of the coil there was no spark, but when I stopped turning the key, for the ignition, it sparked once... Any ideas?