When installing the "O" Rings, grease them up, install the first ring in the top Injector groove. Then roll the 2nd over the first one. This way if you try to get it to the lower groove first, there is a chance of nicking the ring trying to use a pick or small screw driver to pull it out of the top grove etc...
Don`t know if you did this or??? just throwing it out there.
Also, put all 4 caps and hoses together, grease up inside of the caps, then put the 4 on as an assembly. Less chance of a leak this way instead of doing one at a time.
The Diesel should dissolve any grease you put on.
Goat