Have Mercedes Questions? Ask a Mechanic for Answers ASAP
Hi Pete, there are a lot of possibilities for a no start. If you suspect that the water went into the crankcase I would fill the reservoir to the top and crank the motor. If the water gushes out of the reservoir when cranking it tells you that there is a head gasket problem. If the water remains still then there is a good chance that the motor is fine. Next steps are to test for fuel pressure and ignition spark. No fuel pressure indicates a bad fuel pump or relay. No spark indicates a bad crank sensor or other electrical fault. A start and immediate stall indicates a bad key.
Let me know if you have any questions. I can speak to you on the phone today if you would like. There is an additional service fee for the phone call but I can probably help you sort this out a lot faster.
Let me know.