Is the fast clicking when you are trying to turn the engine over, if so its the starter solenoid, is is due to a big drop in voltage from the starter, so much that it can't hold the solenoid open, then from there it then oscillates. Reasons are - flat battery, or fault in starter....the re seems to be some relationship here between the alternator and battery. i'd charge the battery and then it should start, then check the battery voltage with the engine off and with it running and post the results here. cheers Ian