I have a '95 merc sable. if it starts on the first try, it runs great, but if it doesn't start the first try, it won't start. the starter cranks hard, but the engine won't turn over. sometimes i would wait 10-15-30 minutes and go try it again and it would fire right away. I have a new battery within the last year, new starter within the year, and just replaced the fuel filter, i am about to replace the fuel pump. Over the last month or so the issue has been happening more frequently, almost daily now. There seems to be no correlation between time of day, air temp, engine temp, humidity, etc. As far as i can tell there is no common denominator with the issue.