ML350 Bluetec (OM642) random long crank when warm — runs perfect once started

Trying to figure out a weird long-crank issue on my ML350 Bluetec (OM642).

Car always starts, but sometimes it cranks longer than normal, mostly after it’s been shut off for a couple hours. Cold starts are totally fine. Once it fires, it runs perfectly — no rough idle, no smoke, no hesitation. No CEL, no injector smell, no black death.

I can hear the lift pump hum from under the driver seat at key-on / shutdown. Sometimes I also hear a faint hiss, like air equalizing.

One important detail:

I have a low-pressure return hose near the fuel filter that seeps diesel. Not dripping, but it’s always damp if you touch it. It’s held on with a worm/gear clamp, and yeah… I’ve had to snug it up every few months.

From what I’m thinking:

•	It leaks outward when running

•	After shutdown and cooling, the system contracts and might pull air in

•	After sitting warm for 1–3 hours, it needs to purge air before rail pressure comes up → long crank

Cold starts being fine makes me think it’s not injectors or sensors.

I’ve got an iCarsoft MB3 and plan to watch RPM + rail pressure during a bad start.

Plan is to:

•	Replace that return hose section

•	Ditch the worm clamp for a proper fuel/Oetiker clamp

•	Check the plastic fitting on the filter for damage

•	Possibly replace the filter if the barb is compromised

Before I start throwing parts at injectors or a crank sensor, just wanted to see if anyone else has seen warm-only long cranks on OM642 caused by air getting in near the filter/return line.

Appreciate any input 👍