Motorraum: Heavy starter + limp mode

[Erich]

Erlingur,
was that a new starter or a used one? If used, it could also be 'kaputt'. Early motor starters had almost all the inner parts made of plastic, we disassembled my spare starter and that looked like this one
 FIXES - STARTER MOTOR
 FIXES - STARTER MOTOR

You can remanufacture it, you can also use a starter from Bosch for Mercedes Benz if the type is the same, the only difference is the number of teeth on the drive, M70 starter motor has 9 teeth.

the next point to check is the cable from starter, it could look like my cable from the alternator to the B+ pole

 FIXES - ELECTRICAL POWER SYSTEM