I'm losing a lot of fuel around the 4th and 5th injector on my 1985 300D, it drips all over the engine.. because the braided fuel line is starting to wear out--(unless anyone has an alternative idea..) But when I go to order the hose off of shop Forum, they list 2.5 mm, 3mm, 3.3 and 4mm sizes, which kind of confuses me..
The Fuel was spurting like crazy yesteday and my engine was knocking like all h__ and I pulled over and used aUtility Knife and took an extra piece off a lengthy run, but I would like to fix this once and for all.

Finally I would like to find out once and for all why the injectors leak.

Just request injector leak line hose for the '85 300D. I also have an '85 and just replaced all of the leak lines. They usually sell as 1 meter length which is enough to do all 5 injectors.

Make sure you get the line all the way down on the injector nipple. I push it by hand as far as I can go and then gently rock it back and forth with a pair of needle nose pliers.

That should fix you right up.

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Mark Herzig
1995 E300D 153K
1985 300D 142K (sold)
1979 450SL 122 miles (sold)
1992 500E 127K (sold)
1987 300SDL 132K (sold)
1986 300E 161K (sold)