AIR FUEL RATIO CONTROL

FUEL SYSTEM - TM-55-1930-209-14P-9-2_215

WOODWARD PSG GOVERNORS - TM-55-1930-209-14P-9-2_217

TM-55-1930-209-14P-9-2 Water Purification Barges (NSN 1930-01-234-2165) Fuel Oil System Manual
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FUEL SYSTEM SYSTEMS OPERATION The air fuel ratio control limits the amount of fuel to the cylinders during an increase of engine speed (acceleration) 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 (l1) 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 air fuel ratio control. When inlet manifold pressure increases, it causes diaphragm assembly (2) to move towards 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 air 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 (I1) 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 (1I) can now move to let the fuel rack go to the full fuel position. The air fuel ratio control is designed to restrict the fuel until the air pressure in the inlet manifold is high enough for complete combustion. It prevents large amounts of exhaust smoke caused by an air-fuel mixture with too much fuel. AIR FUEL RATIO CONTROL (Ready for Operation) 1. Inlet air chamber. 2. Diaphragm assembly. 3. Internal valve. 4. O01 drain passage. 5. Oil inlet. 6. Stem. 7. Spring. 8. Piston. 9. Oil passage. 10. Oil chamber. 11. Lever. 5

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