1.14.2 Unit Maintenance Functional Description.
Exhaust System. The exhaust system consists of the muffler, exhaust tubing and spark arrester. The
muffler is connected directly to the engine and provides a noise reduction. Exhaust tubing provides an enclosed path for
the released gases from the muffler to the spark arrester.
The spark arrester prevents sparks from entering the
atmosphere and rain from entering the exhaust.
Air Cleaner. The air cleaner provides filtered air to the combustion chamber of the engine. It consists of two
filters that filter the air before it reaches the intake manifold of the engine.
Electrical System (Except Model 350 PAWN). The electrical system (figure 1-3) provides the electrical
control circuits and 12 V dc. Two 12 volt batteries are connected in parallel. The batteries supply the initial starting power.
The electrical wiring harness connects the electrical components of the control panel and engine. When
EMERGENCY-STOP (OFF-ON) switch (S1) is pulled out, S1 contacts connect ammeter (Ml), START switch (S2) and
switch (S4) to positive side of battery. When cooling fan blower belt is installed on engine, S4 contacts 4 and 2 are closed,
connecting OIL PRESSURE BY BASS switch (S3) to positive side of battery. When S3 is pressed, relay (K2) is energized
and normally open contacts of K2 are closed.
Since the contacts of K2 are closed, 12 V dc is applied to fuel shutoff
solenoid (L1). L1 then connects ground to K1 via auxiliary tap (AUX) and K1 energizes. Mechanical linkage is connected
from L1 to the cut-off lever that controls fuel flow into engine. Since L1 retracted, fuel can be injected into engine and
K1 is energized. When K1 is energized, normally open contacts 6 and 8 are closed. Since S2 is pressed, 12 V dc is applied
to starter relay (K3). K3 energizes and provides 12 V dc to starter motor (B1). This causes drive gear of B1 to engage
with engine flywheel and causes B1 to rotate. Rotation of B1 cranks engine until S2 is released. After starting, S2 is
released and 12 V dc is removed from K3. Since no voltage is applied to K3, 12Vdc is removed from B1. When B1 has
no voltage, drive gear of B1 is disengaged from engine and B1 no longer rotates. When oil pressure reaches 4 psi (27.579
kPa), oil pressure switch (S5) closes and S3 is now released. The 12 V dc is till applied to K2 via closed contacts 1 and
3 of K1, which keeps L1 retracted. Alternator (G1) is turned by engine drive pulley and outputs approximately 14V. The
14V then provides 12 V dc to keep K1 and K2 energized. In addition, 14 V from G1 recharges 12 V dc batteries.
Since the engine can be damaged by overheating, V-belt switch (S4) is provided. If the V-belt that turns the cooling fan
breaks, S4 opens, When S4 is open, 12 V dc is removed from K1 and K2. This causes L1 to extend (fuel closed) and
shuts off fuel flow to engine. Since no fuel is provided to engine the 350 GPM pumping assembly is stopped
Since oil provides both lubrication and cooling to the engine, an oil pressure switch (S5) is provided. If engine oil pressure
drops below 4 psi (227.579 kPa), S5 opens. WhenS5 is open, 112 V dc for K1 and K2 is removed. This causes L1 to extend
(fuel closed) and shuts off fuel flow to engine. Since no fuel is provided to engine the 350 GPM pumping assembly stops.
When operation is no longer required, S1 is pushed in and 12 V dc is removed from K1 and K2. This causes L1 to extend
(fuel closed) and shuts off fuel flow to the engine. Since no fuel is provided to the engine, 350 GPM pumping assembly
stops. When an emergency occurs, S1, the emergency stop switch provides rapid engine shut down. Pull position is
normal operation, push position is shutdown,