Usage:
D11N, 776B Tractors;
777B, 785, 789 Trucks
Description of Change: A new fuel injector group is used in the engines in the above machines. The plunger in the new fuel injector group has two scrolls to control the fuel injection timing. The plunger in the former injection pump group had only one scroll. The additional scroll is effective in the lower fuel setting range only. It has no effect on fuel injection timing in the normal operating range. At low idle, the additional scroll retards the fuel injection timing to provide smoother combustion. This will result in lower piston loads and increased piston life.
Adaptable As: When used in complete sets, the new 9Y1785 Fuel Injector Group is a direct replacement for the former 7C2239 Fuel Injector Group in D11N, 776B Tractors; 777B, 785, 789 Trucks.
The fuel delivery rate for the new 9Y1785 Fuel Injector Group is the same as the former 7C2239 Fuel Injector Group so there is no change in fuel setting. However, the new 9Y1785 Fuel Injector Group uses a different timing dimension than the former group. The timing dimension for the new 9Y1785 Fuel Injector Group is 0.5 mm (.02") less than the timing dimension for the former 7C2239 Fuel Injector Group. For example, if the 7C2239 Fuel Injector Group was set at 88.00 mm (3.465"), the new 9Y1785 Fuel Injector Group should be set at 87.50 mm (3.445") to have the same timing. Be sure to refer to the Fuel Setting And Related Information Microfiche (OT) for the correct timing information.