From 1984 until late 1995, the DT engines used a Bosch pump-line-nozzle (PLN) mechanical direct fuel injection system. 1984 through 1992 DTs used a Bosch MW style pump, while the 1993-1995s used a Bosch P style pump, and starting what was called New Generation Diesel engine design, which is still the same basic block design. Mechanical injection was still utilized in trucks up into the 1997 year, but this is rare. In 1994, due to tightening emissions regulations, the engines were redesigned to use electronically controlled unit direct fuel injection. From 1994 to 2004, the engines used HEUI (Hydraulically actuated Electronically controlled Unit Injection) injectors, co-developed by Navistar and Caterpillar Inc.. [https://web.archive.org/web/20070207140102/http://www.internationaldelivers.com/assets/pdf/dyk267.pdf] From 2004 to 2009, the engines use International's Electro-Hydraulic Generation Two (G2) unit injectors.