603 Starting Problems

[Christophe]

Ok. So the '87 300TD runs great but I'm having intermittent trouble starting it lately. Here's what happens.

Most of the time it starts right up with no problem.

But, sometimes it takes a long time cranking it. Up to a minute or two. Then it sputters a bit and then starts up fine. It's like when you change the fuel filter without adding any fuel to it and you have to prime the system.

I wonder if fuel is somehow wicking out or if fuel is somehow being sucked out of the filter.

I just tried changing the filter and I topped up the new filter before bolting it on. It started right up.

Now, this morning it took a long time cranking again....?

Any ideas ?
Thanks
Chris