First of all hi all i am new at this forum i know this forum for a long time but didnt had a mercedes until now (w124 200d om601)

I got a very strange problem :

When im starting the car with cold engine it starts normaly
If i shut down the car right after the start or in 30min or 1 H and i want to start it again it wont start.

I have to glow at least 2 times ( i think to build pressure) to start it

So what could it be ?

I was thinking of a vacuum issue/leak but here they say it cant:

http://www.peachparts.com/shopforum/diesel-discussion/101107-can-vacuum-leak-somewhere-give-you-bad-starts.html