The 5DC17 was often rebranded. If your engine is inside a Toyota forklift (model 5FG or 6FG series), search for the forklift's service manual. Toyota often included Daihatsu engine sections within their documentation.

Understanding the core data of your engine helps in verifying that it is operating within manufacturer parameters. Dihatsu 5dc 17 | PDF - Scribd

Verify fuel quality (minimum 40 cetane) and check for air in the fuel system.

: Designed to operate on Marine Diesel Oil (MDO) or Heavy Fuel Oil (HFO) up to 700 mm²/s at 50°C.

A comprehensive typically spans over 400 pages and is divided into several critical volumes to assist different levels of technical work: Daihatsu Diesel Engine DC17 PDF - Scribd