I have an 83 240D that won't start up. I bought it after it was sitting for about 1 year. I tried a known good battery from my another 300D and it cranked a few times, albeit very weakly and then the starter would not crank any further. I boguht a new battery to replace the dead one in the car and it won't even crank once. I just hear one click when I fully turn the key.

Any way to test the starter? Could it be something else.

FYI, I cleaned the battery terminal connections and the ground from the battery to passenger fire wall.