ARMY TM 9-2805-262-14
AIR FORCE TO 38G2-90-1
NAVY NAVFAC P-8-613-14E
c. Detailed Principles of Operation.
(1) Fuel system. The fuel system is composed of a fuel filter, fuel pump, fuel line, and carburetor. The fuel
filter is a bowl type with a filtering screen. The screen filters dirt and other foreign materials from the fuel. The
fuel pump draws fuel from an external fuel supply through the fuel filter, and delivers it to the carburetor. The fuel
pump, a diaphragm type, is driven by the camshaft. The fuel pump can be operated manually, using the priming
lever. This allows the fuel system, between the pump and the carburetor, to be primed before starting the engine.
The carburetor mixes the air, from the air cleaner, and the fuel. This is then delivered to the combustion chamber
where it is compressed and burned.
(2) Cooling system. The flywheel fan draws cool air into the winterization shroud, where it is then directed
by the cylinder head covers, baffles, and oil pan cover. The airflows around the cylinders and cylinder head
assemblies and cools the engine.
(3) Air supply. The air cleaner cleans the air going to the carburetor. The air cleaner uses a dry fiber
element to remove dirt from the air. As the element gets dirty, airflow through it decreases and creates a vacuum
in the air cleaner. When airflow decreases too much, the service indicator shows a red signal and indicates the
element requires cleaning.
(4) Speed regulation. All four models of the engine are equipped with a centrifugal flyweight governor
connected to the carburetor by a control rod. The governor determines the fastest speed at which the engine will
run. Model 4A032-1 (serial nos. G000001 through G000500) has no speed regulation, other than the adjustment
of the governor. Models 4A032-1 (serial nos. G001001 through G004004), -2, -3, and -4 are equipped with a
throttle control which overrides the function of the governor. The throttle control allows the engine speed to be
adjusted between idle and full governed speed.
(5) Ignition system. There are two different types of ignition systems used on the engine. Models 4A032-1
(all) and -2 use a breaker point ignition system. A set of breaker points triggers a condenser and coil to produce a
high voltage eleotric charge. This charge is then delivered, through a shielded ignition cable, to the spark plug
boated in the cylinder head. This charge creates a spark at the spark plug electrode, and ignites the air/fuel
mixture in the combustion chamber. Model 4A032-3, -4 uses a breakerless ignition system. This system uses
electronic components to generate the high voltage electric charge to ignite the air/fuel mixture.
(6) Lubrication. An oil pump, located behind breaker points, supplies lubricating oil to the internal
components of the engine, cylinder head assemblies, and governor. The engine is equipped with a replaceable oil
filter, which cleans the oil as the engine runs.