distributor problem

i have a peugeot 405 1900 petrol 1992 j reg when i bought it i had it for about a month and it started to cut out on me whilst driving this went on for a few weeks until it cut out one day and i couldnot get it started.i got it back to my house and changed plugs rotor arm leads and cap fuel filter air filter generally giving it a full service however after doing all this it still wouldnt start so i decided to change distributor to get spark what wasnt there this worked and i got it started until now this week it went again and i could not get it started so i changed the distributor again to another one i bought and it started can someone tell me why the distributor keeps blowing i have been told it is the crank sensor but the only sensor i can find is not connected to anything the connection is just lying on top of the rocker cover as if for diagnostic purpose. also i am looking for a complete diagram for the carb of this vehicle which is auto choke