There is only one quick coupler (the brass thing at the hose with a spring loaded collar). The part that goes on the injector adapter is a fitting. Check the shape of that fitting compared to the ones for the glow plugs to see if it is different. Also check the quick coupler o-ring to make sure it has not unseated itself. If it has, lube it with some oil then pop it back in. Also lube the collar with light oil to make it work smoother.

There shouldn't be oil on injectors in a good running engine. What you have maybe fuel from your compression test with the fuel not shut off completely + soot which together look like oil. One way to find out is put the injectors back in, run the engine till fully hot and take the injectors out. They should be dry with just a thin layer of soot.

While your injectors are out, might as well get them pop tested for opening pressure and spray pattern and correct it if there are problems before putting them back in. Don't forget new sealing washers (heat shields) every time an injector is R&R'ed. You gotta plan what to do when pulling injectors and do as much as possible and not use up too many sets of heat shields which add up and gets expensive.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked