FUEL
SYSTEM
Standard
JB
and
JC
engines use a gasoline-
carbureted fuel system to deliver a mixture of fuel and
air to the combustion chamber. The system draws
fuel from a tank, delivers it through a filter and fuel
pump (Figure
12),
to thecarburetor float chamber. Air
passing through the carburetor venturi draws fuel
from the float chamber.
FIGURE
12.
GASOLINE FUEL SYSTEM
CARBURETOR
Options:
A combination gasoline-gaseous fuel car-
buretor or straight gaseous fuel carburetors are
available for use with gaseous fuels. A gaseous fuel
system uses a fuel regulator (Figure 13)to control the
flow of gas from the lines to the carburetor. At the
carburetor, the gaseous fuel is mixed with the in-
coming air.
All fuel system components are described in the
following paragraphs. Select the components that
apply to your engine.
0
CONTROL
REGULATOR
TO CONTROL
TO STARTER
DRY
FUEL FILTER
GAS SOLENOID VALVE
FUELS
Use regular grade gasoline. Premium fuels contain
more Tetra Ethyl lead than regular; the lead quantity
also varies between fuel brands. In constant-speed
operation, the buildup of deposits in the combustion
chambers is proportional to the amount of lead in the
g asol
i
ne.
Excessive lead causes more deposits and more
frequent head removal for cleaning. Engines then
require frequent combustion chamber cleaning.
If fuel is stored for any great length of time, it oxidizes,
forms gums and becomes stale. ONAN recommends
changing fuel asoften as every season to ensure fresh
fuel, especially where there
is
a great change in
weather between seasons.
MAINTENANCE
On gasoline fuel systems, periodic maintenance
consists of cleaning the fuel strainer, cleaning or
replacing the air cleaner, carburetor adjustment and
complete carburetor cleaning.
CARBURETOR
\\
GAS
REGU LATO
R
TO CONTROL TERM.
4
AEPb
/
SHUT-OFF
VALGE
GAS SOLENOID VALVE
NEW SYSTEM
FIGURE
13.
GASEOUS FUEL CARBURETION SYSTEMS
18
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