'91 300D starter location

[dablk1]

My car wouldn't crank this morning. I have 12+ volts at the battery. The battery terminals aren't loose. All lights are working correctly, glow plugs are cycling. Everything is normal other than the fact it just won't turn over. When I turn the key it seems as if it wants to start but there isn't enough power to make it turn over. I think that I've fumbled with pretty everything else on this car since I've owned except the starter. I don't even know where it is. Thanks for your help.