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
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.