Usage:
3500 Family Of Engines;
D11N, 776B Tractors;
777B, 785, 789 Trucks
Description of Change: New fuel injector assemblies are used in the 3500 Family of Engines; D11N, 776B Tractors; and 777B, 785, 789 Trucks. The new fuel injector assemblies have an added balance port hole in the barrel of the plunger and barrel assembly. The balance port hole will reduce side loads on the plunger. This will make the injector assembly more resistant to seizure.
The new fuel injector assemblies also have a change to the plunger which will retard injection timing at low fuel setting positions. This change will provide smoother combustion at low idle, start-up, and low load operation. The change will also reduce loads on the pistons. During medium to higher load operation, the injection is fully advanced to provide optimum combustion characteristics. Prior to the introduction of these new injector assemblies, some injectors had a similar design, but these new injector assemblies provide slightly more retarding. The new injectors will be called "timing retard injectors".
Adaptable To: The new timing retard injector assemblies are direct replacements for the former injector assemblies as shown in Chart A. Some single scroll injectors are also shown in Chart A. These injectors are no longer used for production in the 3500 Family of Engines. Parts service single scroll fuel injectors are available to replace the former single scroll fuel injectors. These are listed in Chart A. Timing retard injectors are also available to replace the single scroll injectors as shown in Chart A. However, the timing retard injectors can be used to replace the single scroll injectors in complete sets only. When timing retard injectors are installed in place of single scroll injectors, the timing dimension specified for the single scroll injector must be lowered by 0.5 mm (.02"). The new timing retard injector assemblies are in effect as shown in Chart B.
