Where are the ground wires for the battery and engine supposed to go?
I've got a '75 300D and the starter is really slow. The negative battery cable is bolted to the inner fender just below the battery box to a scrawny looking flange. Is that right?
I haven't found an engine ground strap yet. Is there one? Should there be?

you almost certainly have an engine ground strap. on my '77 it's on the driver side of the bellhousing. however, a slow starter may just be worn out and unrelated to wiring.

__________________
'77 240D, 504H, OM617.952, etc.

For what it's worth, I replaced my cables when I bought a similar vehicle, and instead of a cable from the frame to the engine, I have a second cable from the (-) battery terminal to the back of the engine block.

I also cleaned up all starter solenoid connections and checked battery voltage and alternator output.

The starter runs noticeably faster

A good ground IS a big deal. Even more so on gas cars.

__________________
Strelnik
Invest in America: Buy a Congressman!

1950 170SD
1951 Citroen 11BN
1953 Citroen 11BNF limo
1953 220a project
1959 180D
1960 190D
1960 Borgward Isabella TS 2dr
1983 240D daily driver
1983 380SL
1990 350SDL daily driver alt
3 x Citroen DS21M, down from 5
3 x Citroen 2CV, down from 6