on my 1992 300d 2.5, the hard injection line from the injection pump to the injector broke just above the nut at the injector on cylinder 5. So I order one directly from Mercedes dealer for $68. Two other dealers in the area had it for $112. So I got a deal right? I put the line on as I was actually able to just snake it around everything. After tightening everything down, fuel was leaking around the top of the nut again at the pump. Its a compression fitting so I'm thinking I screwed that up. Another $68 for the part from the dealer and I put the second one on. I tighten it lightly and start the engine. ITS LEAKING. I tighten more and more and still can't stop the leak.

What's going on here? I asked if there was a O-ring, but the parts guy says no.

Anyone have any ideas?

how tight did you tighten it? Tightening torque is 10-20 Nm or 7-14 ft lbs. Tighten a bit more if needed.

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92 300D 2.5L OM602 OBK #59

Those lines don't have a compression fitting and can be r&r'ed indefinitely.

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83 SD

84 CD

Check the area where the Cone shaped part of the Hard Line seats on the Injector itself for cracks or marks going acrossed the seating area.
If any dirt gets between the Hard Line cone and the seating area on the Injector it will leak. If there was dirt their previously you will see pits where the dirt was squashed into the Metal (the metal of the Injectors is softer than the metal on the Hard line cone).

If you really need to get the car on the road I have more than twice (where I used to work) used a small thin Copper Crush Washer put into the Injector end between the Cone and the Injector. However, you need several crush washers as it does not always want to center on the first try.
Where I worked we had a 1 foot squre box of misc Copper Crush washers and O-rings left over from gaskets kits for rebuilding Fuel Injection Pumps so I do not know where you would buy some tiny Copper Crush washers.

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84 300D, 82 Volvo 244Gl Diesel