Hi everyone, my brother in law recently bought a 93 300sd with a leaking ip, last weekend we were working on the car to replace the delivery valve seals. When we stated the car it felt like it was only running on 5 cyl instead of 6 and blowing alot of black smoke, I started to loosen the diesel hard lines on top of the delivery valves and all of them made a difference in the way the engine ran except for the fourth one? Any ideas what it might be? Thanks Hugo.