I've got a 93 W250 with a leaky injector pump. The pump leaks more when cold than hot. At startup the pump will pour diesel and when hot just a few drips per min. Seems to be on the backside of the pump near where the head is bolted to the injecton pump. other than the leak the truck runs fie. No issued in drivability or cold start ups. So is the leak comming from the O ring sealing the head to the pump or is it a plate on the backside of the pump??? I have tried to see the exact sourse of the leak but it near impossible to find.

 

Same thing mine is doing. On mine, its coming from the o-ring. Mine has been doing it for the last 35K miles or so. You can go a long time with out goofing with it.