1979:

In March 1979, Shinjin Jeep changed its name to Shinjin Motor Co., Ltd. and developed the world's first diesel engine ([Isuzu B Series diesel] 4BA1 model) in November of that year, and started mass production of economical vehicles that can overcome the global oil wave.

Source:
SsangYong Motor > Korando > 1979
http://www.smotor.com/kr/company/center/history/prod/korando/index.html

Isuzu B Series diesel engine:
https://en.wikipedia.org/wiki/List_of_Isuzu_engines#Isuzu_B_engine