I would check the distributor rotor and cap with an Ohm meter. My 1994 E420 had similar symptoms and those parts were evidently burned out internally.

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2004 E500 4Matic 138,000 miles

Pretty sure this E320 has direct ignition with coils and no distributor cap or rotor
Thanks

Hey deanyl!
thanks so much for those wiring diagrams! Hope I spelled your name right..Ive got a fuel pump issue you just addressed with those diagrams! I can see if the FP relay sends power the fuel pumps must run. There is no other component between..Now Im curious how the ECU turns them off when the engine is not runnng..since there seems to be no pressure sensor ...some type of timer? Its gotta be in the system info..

These are broken down much more clearly than any Ive seen..

puzzler, deanyel's post was in September 2011. I haven't noticed any posts from deanyel in years, but have no idea why.

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Fred Hoelzle

yes thanks Ferdman, I was thinking of my own issue not his. But those wiring diagrams are awesome..What would my comment be, a cross comment? my bad of course..these chats have lots of info just by way of coments and references..