e320 cdi w210 (s210) intermittent non-start and cutout when warm

[bigbug]

2002 Avantgarde, She starts fine when cold; but, occasionally cuts-out when warm and quite predictably fails to start when warm. usually a cooling off period helps.
When she fails to start she will crank and usually try to fire-up, often running very rough, before 'dropping off'.
This started in the spring and has gradually worsened, she did go to have codes read (reputable independent) and there were some, but not wishing to cast aspersions... nothing immediately helpful.

I have read numerous accounts of similar issues, sadly the majority without clear indication of if it was ever resolved.
Maybe you have previously found the answer or helped someone with this class of problem?

Back in the days.. this would have been either the crank or cam position sensors, frustration caused me to swap these out but no change.
It can be seen that some bubbles are entering the fuel (diesel) line after the filter at high revs, but nothing before, apparently this is normal?
Checked the in-tank fuel strainer, clear, and also had a fuel vacuum gauge on the input to the filter and that looked (sorry no values) OK. No electric fuel pump on her, just HP pump vacuum.

Down to taking advice from people in filling stations when she won't start, some insightful and some just downright obnoxious.

 

[nick mercedes]

When this happened to my Vito it was the sensor on the thermostat.

Fine in the mornings, but if I stopped for diesel it was a nightmare.

 

[bigbug]

When you say, sensor on the thermostat, this being the coolant temperature?
Love to see the path for that interaction, but, I am keen to try anything on this as it's really obscure, don't know if anyone knows why these MB's do this

 

[bigbug]

<solved>

<solved>
Not long after posting I spotted a drip, followed it back and found the wet patch, so changed the easier to get at HP pump fuel line o-rings, leaving the more tricky ones.
Low and behold, she was very much improved
But the starter had suffered, all that cranking???, it would spin but not engage reliably.
This weekend I found the time to look at the starter, couldn't see anything out of whack so gave it a clean, applied some appropriate lube and put her back in. Most improved starter for least cost, see if it lasts!
Couldn't fail to notice the new diesel leak, regular drip onto fan belt !
Those o-rings I avoided, they've now been done and it's not really as bad as folk make out.
Getting the radiator cowl out is just daft, but removing that and the turbo intake gives enough room.
Credit to whoever suggested wire around the connectors to help pull them free TY
The o-rings for this job are know by MB as the
!!! green diesel o-rings !!!
and cost pennies. They have an expected lifespan of about 10~11 years, got nearly 15 out of mine but could have stretched to replacing them a little earlier!