For me, the testing/ diagnosing of the components is to gain knowledge. By just replacing the entire system, you haven't learned anything and will make the same mistake(s) next time.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked