I have a repair shop that specializes in diagnostic and electrical, but typically not on imports, I agreed to look at an '86 420 SEL for one of my customers, it had been stored in cold storage last winter, it ran good when parked, but now it only fires while cranking, this is a fuel pump relay type of problem, spark is good, fuel pressure is good, while the F.P. relay is energized, I have a Mitchell system, so I have a decent wiring diagram, but without understanding the whole process of the injection system, it has been difficult to diagnose, also the tach is not working, one would assume that they are related, also the cold start valve has no power to it, and I see by the wiring diagram that it receives power from the fuel pump relay, if anyone has any idea, i could really use the help. thanks Chad