Signs of sick starter,fully charged battery and slow rotation speed.Car will not take a jump.You beat starter with a tool and she starts.
Raise car high enough to slide under drivers side of car.Disconnect battery ground.DO BLOCK WHEELS,and SET PARKING BRAKE.
Tools needed 16mm open end wrench,16mm socket and ratchet,12mm open end wrench, and 10mm open end wrench.
Crawl under car you will see the two 16mm bolts going into bell housing into the threaded starter.Start with top bolt yes you can only get a quater of a turn.Bottom bolt will take 16mm socket remove as other.Locate oil sending unit and unplug.Now that starter has dropped down some you will see on starter a 10mm bolt holding wire harness remove(optional to put back).Now starter should come down to where you can unplug one wire and use 12mm wrench to remove other wire.
Installation is reverse.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt