Mixer Assembly - Kubota WG1605-E3 Diagnostic Manual

WG1605-G-E3,WG1605-L-E3,WG1605-GL-E3, DM
MIXER ASSEMBLY (L, N, LN, GL, GLN)
The air valve mixer is an air-fuel metering device,
and is completely self-contained. The mixer is an air
valve design, utilizing a relatively constant pressure
drop, to draw fuel into the mixer from cranking, to full
load. The mixer is mounted in the air stream, ahead of
the throttle control device.
When the engine begins to crank, it draws in air, with
the air valve covering the inlet, negative pressure begins
to build. This negative pressure signal is communicated
to the top of the air valve chamber, through 4 vacuum
ports, in the air valve assembly. A pressure/force
imbalance begins to build, across the air valve
diaphragm, between the air valve vacuum chamber, and
the atmospheric pressure, below the diaphragm. The air
valve vacuum spring is calibrated, to generate from
101.6 mm (4.0 inches) of water column at start, to as
high as 355.60 mm (14.0 inches) of water column, at full
throttle. The vacuum being created is referred to as Air
Valve Vacuum (AVV). As the air valve vacuum reaches
101.6 mm (4.0 inches) of water column, the air valve
begins to lift against the air valve spring. The amount of
AVV generated is a direct result of the throttle position.
At low engine speed, the air valve vacuum is low and the
air valve position is low, thus creating a small venturi, for
the fuel to flow. As the engine speed increases, the AVV
increases, and the air valve is lifted higher, thus creating
a much larger venturi. This air valve vacuum is
communicated from the mixer venture, to the DSR
secondary chamber, via DEPR and the low pressure fuel
supply hose. As the AVV increases in the secondary
chamber, the secondary diaphragm is drawn further
down, forcing the secondary valve lever to open wider.
The DEPR maintains the precise fuel control to the
mixer, despite the air valve position, and AVV being sent
to the DSR secondary chamber. The mixer acts as the
secondary fuel metering device, and delivery device, in
the EControls emission control systems. The mixer is
attached to the Electronic Throttle Body (ETB), via an
adapter. The adapter is fitted with specific spacers and
o-rings, to insure a seal tight fit, with the ETB.
The Mixer is designed such that the air valve
diaphragm assembly can be replaced, should the
diaphragm be damaged, during operation, from fuel
contaminants. Refer to Mixer Diaphragm Replacement
section in this manual. The Mixer utilized on USA
emission certified engines are a critical part of the
certified emissions system, and do not require any
periodic adjustment. The mixer does not have any
external nor internal adjustments.
Figure 16: Mixer and ETB Adapter
1-50
ECM SYSTEM
KiSC issued 12, 2016 A