Mike, My thought process is as follow:
I am having hard start issues when ever car sits for couple of hours. In the mornings it start much better than afternoon, takes long cranks at afternoon. I guess in the cold start CSI kicks in and helps better start but still not a quick response as it use to before the problem. After cold start it runs a rough for few seconds and then idles and runs like charm. I search the forum and it sounds like "Vapor lock" issue caused by fuel pressure loss. One of the item mentioned in the forum over and over again is the Fuel accumulator in similar situations. Since I had one from 500SEL, I was wondering if it is compatable or not. I just want to validate the resolution, if it is the fuel accumulator I will definately buy a new one but don't want to spend $120 to find out that was not the issue. Some other items on the list to check are check valve, fuel regulator, EHA O rings, Fuel Filter etc, the car definately seems like loosing fuel pressure once sits for few hours. I wold chekc the fuel pressure once I get the coupling to attach the guage to the line. I already checked the duty cycle for lamda and it is 45-50%, The ignition wires, cap, rotor, plugs etc was changed 3K miles ago, and since the car runs fine otherwise it does not seems to be electric related problem.
I could very well be wrong and chasing the wild goose, so please help me out if I am on the wrong track.
The car is 1987 420SEL.
Thanks in advance

__________________
87 420 SEL
Looking for a nice mid 80's MB diesel.
87 BMW 528e (Sold)
99 TOYOTA 4Runner
1989 Honda Accord (Sold)
1988 Honda Accord (Total)