A couple of German Mercedes mechanics (father son team who spoke German while working on the cars...) told me to never use starting fluid or WD40 to start these diesels because it can snap the timing chain. Since both of these men have forgotten more about these cars than I will ever know, I listened and nodded in agreement.....

note; I've gotten away using WD40 before they told me this. Since then, I've never used it.....if it won't start using normal methods, then I'm not going to risk snapping the timing chain just to make myself happy.