This could be a major pain to check but it happend to my 75. For me the cog/linkage, from my ignition cylinder to the rod linkage that actually physically moves the ignition switch from "off" to "accessory" to start,was totally sheared off. Thus the key and cylinder were turning but it was doing absolutely nothing to the car. Dont know if you can see from picture. If this is your problem good luck. To fix you will have to remove steering wheel, turn signal, ext.