why doesnt my 1993 honda civic 1.5 si automatic start sometimes?

my 1993 honda civic 1.5 si automatic will not start on a regular basis but then it does after trying for 10 - 15 mins, with the transmition in n or p i turn the ignition to position 2, the engine light goes on the off and i turn the key to position 3, the starter motor turns the engine over but the engine will not start, i play around with ht leads spark plug caps dist cap etc repeated times and when im just about to give up it starts, ive noticed that when its going to start i turn the ingnition to position 2 and when the engine light comes on i hear a sound for a second then it will start but when it does not start i dont hear this sound, i think its something to do with fuel flow and the electrical workings of but im just guessing, any help would be much appreciated.