Service Manual

LPG FUEL SYSTEM
Refer to Figure 9-4. The carburetor, gas pressure
regulator, air pump and vacuum sustain valve com-
prise the
LPG fuel system components that are part
of the engine assembly.
A vacuum cutout device is
provided by the equipment manufacturer.
The carburetor should not require service and there
are no replaceable parts or adjustments except for
the low idle speed screw.
WARNING Carbon Monoxide (CO) Is deadly!
The Idle mixture screws
on the carburetor and
gas pressure regulator are factory set and
sealed.
DO NOT READJUST.
Note: It is the responsibility of the user to make cer-
tain that indoor carbon dioxide regulations are met.
Referring to the block diagram,. operation of the
LPG fuel system is as follows:
1. Crankcase vacuum pulses cause the air pump
to pump clean air from the air cleaner to the
vent side of the gas pressure regulator, which
has a factory adjusted and sealed bleed valve.
This provides for a precisely adjustable flow of
gas for proper idle mixture.
2. The vacuum sustain valve consists of a check
valve and bleed-off
orifice. It bleeds off crank-
case vacuum when the engine stops to cause
the vacuum lock-out device to shut off the gas
supply. The check valve removes the vacuum
pulses permitting the
lock-out device to open
during cranking.
The air pump
is identical to the gasoline fuel pump
See the instructions that follow in this section for
illustrated in Figure
9-3.
governor, choke and speed adjustments.
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PEED SCREW I I
LPG SUPPLY TANK
L----,,,
LPG CARBURETOR I
CRANKCASE VACUUM I
VACUUM
PULSES
Device
AIRPUMP
PRESSURIZED
AIR REGULATOR
PRESSURE
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t
AIR CLEANER I
FIGURE 9-4. LPG CARBURETOR AND FUEL SYSTEM BLOCK DIAGRAM
9-5