I have a 1988 420sel that runs ecellent when it runs. First noticed problem that engine would die when I made a right turn. Would instantly restart and down the road I would go. Now, I can be driving in my neighborhood, and the engine will stall. Roll to a stop, try to restart, and it takes a couple tries for the engine to start. Sits there and runs, go driving and it will stall again. Let it sit and run in driveway and it will run for a while and then just stall. New fuel filter today, new fuel inlet line, new sparkplugs as Mercedes reccomends, and it still stalls. When running, runs without missing, smoking, just quiet and smooth. My guess now is fuel pump relay. Am I going in the right direction? Buy new or are used ok. This from what I can read is an issue when they get older. Help. Steve

Hello,
I have the same problem (86 420 165K) and have had same for over 1 year.
I have replaced the fuel pump relay checked OVP relay replaced the CPS ($275)
Gone thru entire fuel system, replaced filter checked pumps, checked all wiring etc., etc.,and it still stalls going around corners!
Someone has fixed this specific problem sometime somewhere before.
Please let me know if you find them?
Dave (AMCO)