Smoke on cold start

My 1987 300 SDL smokes badly on cold start up----replaced glow plugs thinking that was problem but still smokes very badly on cold start-----doesn't smoke at any other time---no smoking on warm start....Car runs fine-----188000 miles..Is there a temperature sensitive sensor that richens fuel supply when engine is cold and could this be mal-functioning? Would appreciate any and all help-----I don't have much mechanical knowledge....