Usage:
776B Tractors;
777B, 785, 789 Trucks
Reference: Service Magazine; July 25, 1988; Page 8; "Replacement Fuel Injector Nozzles With New Nose Cones Available."
Description of Change: A new governor and improved injector nozzles are used to reduce excessive black exhaust smoke. Also, new turbochargers are used in the 785 and 789 Trucks. The new governor has a new smoke limiter that will eliminate internal wear which causes a degradation to the smoke limiter setting. The limit setting of the smoke limiter is reduced from 2.00 mm (.079") to 1.00 mm (.039"). In addition, a stiffer spring is used against the diaphragm. The stiffer spring will cause the control to react somewhat slower and reduce the transient smoke during engine acceleration.
The new turbocharger has a different turbine housing to provide more boost and less smoke. The new turbine housing has a smaller nozzle.
The improved injector nozzles have a different spray angle to provide optimum combustion.
Adaptable To: The new 7E7249 Governor Group, for the 776B, 777B, 785 and 789 Trucks, is a direct replacement for the former 9Y7559 (canceled) Governor Group. The improved 7C2238 Injector Nozzle Assembly can be identified with date code "F9" or later.
The new 7E9492 Turbocharger Group, for the 785 Trucks, is a direct replacement for the former 9Y1490 (canceled) Turbocharger Group. The new 7E9497 Turbocharger Group, for the 789 Trucks, is a direct replacement for the former 9Y8266 (canceled) Turbocharger Group.
The chart identifies the effective machines or engines.
The new and improved components are adaptable to first production on all machines (engines).
NOTE: If one turbocharger is updated, update all the turbochargers on the machine. The former turbocharger group can be updated to the new turbocharger group by replacing the former turbine housing. For 789 Trucks, replace the former 9Y8270 Turbine Housing with the new 7E9496 Turbine Housing. For 785 Trucks, replace the former 4W6907 Turbine Housing with the new 4P0527 Turbine Housing.