What kind of car? M103 is in a few different models.

You say the motor cranks slowly..... Typically this is electrically related - bad ground or corroded battery terminal or wire. Seeing as how a new battery (is it still in there?) didn't fix the issue, I would check the battery cables very carefully and replace them if in doubt. As they become corroded, they lose the ability to carry current, even though the voltage is fine until you crank. The added resistance drops the system voltage when any significant current is drawn.

Sounds like your bad connection caused your voltage to drop until the engine died because you weren't charging adequately. The new battery didn't alleviate it because the connection is too poor to allow sufficient current for cranking and voltage to operate the computers and ignition.

That's my theory, anyway. If it isn't an electrical issue, then your motor is trying to seize up............

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-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition