NUT-JAM 1D5117 - Caterpillar

Introduction
For Specifications with illustrations, make reference to SPECIFICATIONS for 3304B & 3306B GENERATOR SET ENGINE ATTACHMENTS, Form No. SENR2798. If the Specifications in Form SENR2798 are not the same as in the Systems Operation and the Testing and Adjustment, look at the printing date on the back cover of each book. Use the Specifications given in the book with the latest date.Fuel System
Fuel Ratio Control
FUEL RATIO CONTROL (Engine Started)
1. Inlet air chamber. 2. Diaphragm assembly. 3. Internal valve. 4. Oil drain passage. 5. Oil Inlet. 6. Stem. 7. Spring. 8. Piston. 9. Oil passage. 10. Oil chamber. 11. Lever.
FUEL RATIO CONTROL (Control Activated)
1. Inlet air chamber. 2. Diaphragm assembly. 3. Internal valve. 4. Oil drain passage. 5. Oil inlet. 6. Stem. 7. Spring. 8. Piston. 9. Oil passage. 10. Oil chamber. 11. Lever.The fuel ratio control limits the amount of fuel to the cylinders during an increase of engine speed (accleration) to reduce exhaust smoke.Stem (6) moves lever (11) which will restrict the movement of the fuel rack in the FUEL ON direction only.With the engine stopped, stem (6) is in the fully extended position. The movement of the fuel rack and lever (11) is not restricted by stem (6). This gives maximum fuel to the engine for easier starts.After the engine is started, engine oil flows through oil inlet (5) into pressure oil chamber (10). From oil chamber (10) oil flows through oil passage (9) into internal valve (3) and out oil drain passages in stem (6).Stem (6) will not move until inlet manifold pressure increases enough to move internal valve (3). A line connects the inlet manifold with inlet air chamber (1) of the fuel ratio control.When inlet manifold pressure increases, it causes diaphragm assembly (2) to move toward the right. This also causes internal valve (3) to move to the right. When internal valve (3) moves to the right, it closes oil passage (9).When oil passage (9) is closed, oil pressure increases in oil chamber (10). Oil pressure moves piston (8) and stem (6) to the left and into the operating position. The fuel ratio control will remain in the operating position until the engine is shut off.When the governor control is moved to increase fuel to the engine, stem (6) limits the movement of lever (11) in the FUEL ON direction. The oil in oil chamber (10) acts as a restriction to the movement of stem (6) until inlet air pressure increases.As the inlet air pressure increases, diaphragm assembly (2) and internal valve (3) move to the right. The internal valve opens oil passage (9), and oil in oil chamber (10) goes to oil drain passage (4). With the oil pressure reduced behind piston (8), spring (7) moves the piston and stem (6) to the right. Piston and stem (8 and 6) will move until oil passage (9) is closed by internal valve (3). Lever (11) can now move to let the fuel rack go to the full fuel position. The fuel ratio control