Is the no-start condition a complete no start or just longer and longer crank times before ignition? Bad CSS that car won't start at all (including the EZL 99% of the time) Longer cranks might be a leaky injector...my two cents based on what I've read. Also, not sure if there's a check valve or not on the fuel pump itself on the 124 e320s. Also could be a starting issue.

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1995 E420
1998 SL500 Sport
2009 E350 Sport
1995 S500 Coupe
1992 500 SEL