F U E L S Y S T E MTM 5-3805-258-24-1S Y S T E M S O P E R A T I O NThe air fuel ratio control limits the amount offuel to the cylinders during an increase of enginespeed (acceleration) to reduce exhaust smoke.Stem (6) moves lever (11) which will restrict themovement of the fuel rack in the FUEL ON direc-tion only.With the engine stopped, stem (6) is in the fullyextended position. The movement of the fuel rackand lever (11) is not restricted by stem (6). Thisgives maximum fuel to the engine for easier starts.After the engine is started, engine oil flowsthrough oil inlet (5) into pressure oil chamber (10).From oil chamber (10) oil flows through oil pas-sage (9) into internal valve (3) and out oil drainpassages in stem (6).Stem (6) will not move until inlet manifold pres-sure increases enough to move internal valve (3).A line connects the inlet manifold with inlet airchamber (1) of the air fuel ratio control.When inlet manifold pressure increases, it causesdiaphragm assembly (2) to move towards the right.This also causes internal valve (3) to move to theright. When internal valve (3) moves to the right,it closes oil passage (9).When oil passage (9) is closed, oil pressure in-creases in oil chamber (10). Oil pressure movespiston (8) and stem (6) to the left and into theoperating position. The air fuel ratio control willremain in the operating position until the engineis shut off.When the governor control is moved to increasefuel to the engine, stem (6) limits the movementof lever (11) in the FUEL ON direction. The oilin oil chamber (10) acts as a restriction to the move-ment of stem (6) until inlet air pressure increases.As the inlet air pressure increases, diaphragmassembly (2) and internal valve (3) move to theright. The internal valve opens oil passage (9),and oil in oil chamber (10) goes to oil drain pas-sage (4). With the oil pressure reduced behindpiston (8), spring (7) moves the piston and stem(6) to the right. Piston and stem (8 and 6) will moveuntil oil passage (9) is closed by internal valve (3).Lever (11) can now move to let the fuel rack go tothe full fuel position. The air fuel ratio control isdesigned to restrict the fuel until the air pressurein the inlet manifold is high enough for completecombustion. It prevents large amounts of exhaustsmoke caused by an air-fuel mixture with too muchfuel.AIR FUEL RATIO CONTROL(Ready for Operation)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.3-10.1/3-10.2 (blank)
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