Found a very small fuel leak coming from the line near the primer pump (new style).

It is so small that I almost missed it. Don't know if this could be the problem or just part of it.

Got the parts ordered today...

I'll see.

Thanks everyone for your much appreciated help.

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1980 300TD(euro non turbo): Eng: 617.912 /Tran:722.118
1985 300SD: Eng: 617.951/Tran: 722.416