HOUSING 3792560 - Caterpillar

Control Linkage for the Fuel Injection Rack
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Unit injectors and rack control linkage (1) Lever (2) Torsion spring (3) Shaft (4) Rack (5) Synchronization screw (6) Clamp (7) Clamp assembly (8) Fuel setting screw (9) Link (10) Lever assembly (11) Unit injector
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Unit injector and rack control linkage (1) Lever (A) FUEL ON (B) FUEL OFF (3) Shaft (4) Rack (5) Synchronization screw (6) Clamp (11) Unit injectorThe rack control linkage connects the governor output to unit injector (11) at each cylinder. The governor output shaft is pinned to link (9). The link is connected to lever assembly (10). When the governor demands more fuel, link (9) and lever assembly (10) cause rotation of shaft (3) and clamps (6). Shaft (3) and clamps (6) are rotated in a FUEL ON (A) direction. Each clamp then pushes lever (1) as the shaft rotates. Rack (4) is pulled by lever (1). This will allow more fuel to be injected into the cylinder.When the governor requires less fuel, link (9) causes rotation of shaft (3) and clamps (6). Shaft (3) and clamps (6) are rotated in a FUEL OFF (B) direction. Lever assembly (1) is forced to rotate clockwise by torsion spring (2). This will push rack (4) toward the shutoff position. A torsion spring is located at each unit injector. This allows the rack control linkage to go to the shutoff position, even if one fuel injector rack is stuck open.The power setting of the unit injector for the No. 1 cylinder is made with fuel setting screw (8) in clamp assembly (7). As fuel setting screw (8) is turned, shaft (3) rotates to a new position with respect to link (9) and lever assembly (10). Adjusting screws (8) allow synchronization of the injectors to the unit injector of the No. 1 cylinder.Governor
The governor transfers the operator's requirements to the fuel injector rack control linkage. The governor receives the desired engine speed by the position of the throttle. The governor output shaft immediately moves when the throttle is moved. The motion of the governor output shaft will cause the fuel injector rack control linkage to rotate. This will move the fuel injector racks. The change in the position of the fuel injector rack will cause a change in the speed of the engine. As the speed of the engine changes, the governor will adjust the amount of fuel that is delivered. This will cause the engine to stabilize at the rpm that corresponds to the throttle position. For further information, refer to Service Manual, SENR6454, " 3114, 3116, and 3126 Engine Governors (MUI)".Fuel Ratio Control
The turbocharged engine uses a fuel ratio control (FRC) in order to control smoke during acceleration at low boost levels. The FRC restricts the amount of fuel to the combustion chambers until sufficient boost has been achieved.
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Governor linkage and fuel ratio control schematic (A) FUEL ON output (B) FUEL ON input from operator (1) Governor output shaft (2) Inlet port (3) Fuel ratio control (FRC)