DF5 0001 subsequently underwent testing at Fengtai West Station yard, which provided data for further enhancements to improve the performance and reliability of the locomotive.

In 1983, the Dalian works redesigned the 8-cylinder inline 8240Z, turning it into a V8 with equal performance, designated 8240ZJ; in 1984, the first Dalian-built unit, DF5 1001, left the factory and was assigned to the Jinan locomotive depot for service testing.

The redesigned locomotive not only eliminated the excessive vibration and other shortcomings, but improved significantly upon the initial and continuous tractive effort.

At least eight units have been delivered second-hand to the Korean State Railway, where they work on local passenger and freight as well as shunting duties around North Korea, including at P'yŏngyang and Namyang.

[4] They are numbered 내연101 to 내연108 (내연 = Naeyŏn, "internal combustion") and retain the blue and white China Railway livery.