Toro Workman 3000 Series Service Manual page 431

Application
The Liquid Propane (LP) Gas Conversion Kit is installed
to replace the gasoline fuel system on the Mitsubishi
3G83 liquid cooled engine. With the kit installed, only LP
gas can be used to fuel the engine. LP gas is used for
cleaner emissions over conventional gasoline. The car­
buretor is left intact.
Major Components (Fig. 3)
LP gas is stored in the 20–lb. fork lift style fuel tank. The
tank has a fuel gauge. LP gas is delivered to the vacuum
fuelock–filter through a LP gas hose assembly. The hose
has a female quick fitting that attaches to the fuel tank.
Both the tank and hose assembly automatically stop fuel
flow should a rupture or high fuel flow rate occur in the
fuel system.
The vaporizer–regulator allows LP gas to vaporize and
expand. Attached to the vaporizer–regulator is the vacu­
um fuelock–filter. The vacuum fuelock–filter stops fuel
flow when the engine is not operating.
The mixing adapter controls the air/fuel mixture when
the engine is operating faster than idle speeds. It is lo­
cated in–line of the air inlet hose between the air cleaner
and the carburetor.
Operation (Fig. 3 and 4)
With the engine off and the cutoff valve on the fuel tank
open, LP gas (150 PSI nominal to 250 PSI maximum) is
supplied as a liquid to the vacuum fuelock–filter. The
vacuum fuelock–filter is shut and no fuel enters into the
vaporizer–regulator.
When the ignition switch is turned to the START position,
the starter motor and starting valve are energized. As
the engine rotates, a vacuum signal is transmitted from
the air intake manifold, through a vacuum hose (run),
and to the vacuum fuelock–filter and vaporizer–regula-
tor. The signal opens the vacuum fuelock–filter to allow
LP gas flow to the vaporizer–regulator and unlocks the
vaporizer–regulator to allow LP gas flow into its primary
chamber. Also, engine vacuum draws fuel through the
vaporizer–regulator's primary and secondary cham­
bers, through the starting valve, and then directly into the
carburetor's air intake chamber while the engine is
cranking.
When the ignition switch is released to the RUN position,
the starter motor and starting valve are deenergized.
The engine now is running on its own power and produc­
ing sufficient vacuum to keep the vacuum fuelock–filter
open and the vaporizer–regulator unlocked.
Workman 3000/4000 Series
Liquid Propane (LP)
Fuel Tank
Air
Air
Mixing
Cleaner
Adapter
Fuel entering the primary chamber of the vaporizer–reg-
ulator vaporizes and expands to a pressure of 4 to 5 PSI.
During the expansion and vaporization process, heat is
removed from the LP gas. Engine coolant passes
through the vaporizer–regulator so heat is added back
to the fuel after the engine warms up. The vaporized LP
gas is then released to the secondary chamber of the va-
porizer–regulator.
The vacuum of the engine draws air through the air
cleaner, mixing adapter, and carburetor to the engine.
The inside of the mixing adapter acts as a venturi that
creates a negative pressure that draws vaporized fuel
from the secondary chamber of the vaporizer–regulator.
The fuel flow out of the chamber varies closely with air ­
flow. A fuel–metering device (orifice) is connected to the
mixing adapter in–line with the vaporizer–regulator. The
orifice regulates the fuel entering the adapter, which re ­
sults in a consistent air/fuel mixture to the engine. The
mixture is determined by the design of the components
and is not adjustable. The fuel/air mixture obtained at
idle speed and starting is controlled by a screw adjust­
ment at the vaporizer–regulator. At idle speed, the ven­
turi pressure signal is not sufficient to draw fuel into the
adapter. To provide sufficient fuel flow at this low speed,
the vaporizer–regulator has an idle screw adjustment
that will make sure a minimum amount of fuel flows to the
mixing adapter.
After the air/fuel mixture leaves the mixing adapter and
enters the carburetor, the carburetor is used as throttling
device to change the air/fuel mixture flow rate into the
engine. Once in the engine, the fuel is consumed in the
same manner as a gasoline engine.
When the ignition switch is taken to the OFF position,
electrical power is interrupted to the spark plugs. Ignition
in the engine stops and the shuts down. Once the engine
slows down enough, engine vacuum will not be sufficient
enough to keep the vacuum fuelock–filter open and the
vaporizer–regulator unlocked. The vacuum fuelock–fil-
ter shuts and the vaporizer–regulator locks. Fuel flow is
stopped to the vaporizer–regulator, mixing adapter, and
the engine.
Page 11 – 7
Rev. D
LP Gas (Liquid)
LP Gas
(Vapor)
LP Gas
(Liquid)
Vaporizer–
Regulator Lock–Off
LP Gas
Starting
Carburetor
Valve
Mitsubishi
3G83
Engine
Figure 4
Liquid Propane Gas Conversion Kit
Fuel
Engine
Vacuum