mercedes e320 No Spark


Our car stopped while driving along , checked the fuel system but is fine ,checked the spark, no spark but motor turning over good . Replaced the coils with new ones  and they have power to coil but no spark at plug when turning over. The central locking seems to be working fine as I know this can stop motor from starting but will turn over fine . Have checked the main fuses and all look to be good . does anybody know of anything else that could stop the spark from working I am running out of things to try. Please HELP.