American-Lincoln
®
1-37
SC7740
GENERAL MACHINE MAINTENANCE - Cont.
LP GAS SYSTEM
The propane powered Model SC7740 is identical to the “standard” gasoline powered SC7740, except its fuel
system has been modified to operate on LP vapor.
The LP fuel system consists of several components not found on the gasoline system. The LP fuel system also
contains the associated mounting hardware and plumbing for the LP components. The major LP components
are as follows:
1.
An LP carburetor
2.
A combination water heated vaporizer and regulator
3.
A combination LP fuel line filter and lock off valve
4.
An LP fuel tank and fittings.
These components are factory set; attempts at adjusting these components should only be made by authorized
service personnel.
LP GAS VAPORIZER-REGULATOR QUICK CHECK
Turn on the key switch and open the radiator cap. Check the coolant for bubbles. If bubbles are present, the
vaporizer may have a leaking gasket or may have developed a pinhole leak, allowing the LP fuel to enter the
cooling system.
LP GAS FUEL TANK
The LP tank is located under the driver’s seat. Use only the proper size and type of LP tank. The SC7740 LP
powered sweeper/scrubber uses a 33.5 lb. Liquid withdraw tank. The DOT designation of the tank is DOT 4BW-
240.
LP LIQUID WITHDRAWAL SYSTEM
The liquid LP fuel flows from the LP tank under its own pressure to the pressure relief valve. This valve is normally
closed, which prevents LP fuel from escaping into the atmosphere. This LP gas is then piped to the LP fuel filter
lock. The fuel filter lock removes unwanted tank scale and deposits from the LP gas. The vaporizer converts the
liquid LP fuel into a gaseous LP fuel. This gaseous LP fuel is sent to the primary regulator. The primary regulator
reduces the pressure of the LP tank and makes the flow more constant. The secondary regulator reduces LP
gas pressure to the level required by the carburetor. From the secondary regulator, the LP fuel is piped to the
carburetor where it is finally metered into the air flow which is sent to the combustion chamber.