HELP!!!! i have taken the car to the dealer to run a diagnostic to address the following
WHEN ATTEMPTING TO START VEHICLE, ON OCASSION VEHICLE WILL NOT START, ENGINE WILL NOT CRANK OVER, HOWEVER FUEL
COVER WILL POP OPEN AND TAILGATE WILL UNLOCK. AFTER ATTEMPTING TOCRANK AGAIN VEHICLE WILL EVENTUALLY START (Sorry for the CAPS i took that from the diagnostic Report)
The Diagnostic report continues with Mechanics comments:
verified concern, found vehicle not starting and the symptoms are occurring. checked voltage during cranking and found dropping very low likely causing electrical issues due to control units losing required voltage. battery at 9.7v intermittently with no load. performed battery test on main battery and eco start and stop battery and found both failing and requires replacement. various codes in vehicle for low voltage. no bus keep awake events in ezs and onboard system data show no events.

The reco was to replace both Batteries.. which was done and the problem persists... initial Key turns in the morning, results in a failed start but the engine tries to turn over and then nothing... after several turns the engine will start.. but the gas cover opens and the rear tailgate will open. Once it has started there is no issues with he car.. the ECO starts work every time... If the car has been running for some time, it starts every time on the initial turn.

I have also replaced the
A0025427219 Fuse Relay Box, Electrical Fuse Box Relay A0025427219 Multipurpose Air Suspension Compressor Fuel Pump Relay for A B C Class to no avail

Any ideas? Could this be an alternator issue? i would assume that if it was the on board would see low amperage and go into Limp mode... that has never happened.

Could it be the Voltage converter module?

 

Did your mechanic scan it for codes? All MBs of this era have a problem with the Electronic Ignition System (EIS) where a loose solder joint means the car will start sometimes and other times not. Search for EIS on the W164 forum (same part as W245). Also plenty of youtube videos on the subject. Can be a DIY if you're handy.

Ask your mechanic for the results of the scan. His advice to change the battery was the right one at 9.7 volts and you cant diagnose these cars for electrical faults with a dying battery so you've lost nothing there.