THEORY OF OPERATION -- CONTINUED
FUEL SYSTEM -- CONTINUED
Fuel Purge System A manually operated purge pump is provided in the vehicle operators compartment and is
used to clear the engines main fuel system of air and fill it with fuel. Most of the purged air is removed through
bleeder valves, located in the top of the primary fuel filter and the fuel/water separator filter. The rest of the air is
forced through the main fuel tubes into the fuel return lines and on to the vehicle fuel tanks. Water is removed from
the system by a constant bleed orifice in the primary fuel filter and an automatic water drain in the fuel/water sepa-
Fuel Filters (Figures 1--1 and 1--2). The replaceable element type primary fuel filter is mounted on the right front
of the engine and is equipped with a constant bleed orifice and drain line which constantly removes a metered
amount of fuel, and returns it to the main fuel tank through the fuel injector nozzle drain lines. This continuous
drain, from the bottom of the filter, removes water in the free state that has been filtered from the fuel by the prima-
ry fuel filter element. The replaceable element fuel/water separator type filter is mounted on the left front of the
engine. Fuel from the vehicle fuel tank passes through the primary filter before entering the engine fuel pump. The
pump delivers fuel to the fuel/water separator filter and on to the fuel metering pump. Excess fuel provides pump
cooling as it flows through the fuel metering pump hydraulic heads and is returned to the fuel tanks (Figure 1--9).
The fuel/water separator filter unit has three replaceable elements and contains a chamber for collecting water.
The two outer elements are coalescer elements and will remove emulsified water that has passed through the pri-
mary filter. The center element is a fuel filter element. The water removed from the fuel is automatically drained
from the filter housing. Two water sensing probes are located in the filter housing. When the water level reaches
the upper probe an electrical circuit is completed, a solenoid valve opens and allows the water to drain. The valve
closes when the water level reaches the lower probe. A drain cock is installed so the fuel/water separator may be
drained manually. The unit provides moisture--free and uncontaminated fuel to the injection pump. Both the prima-
ry filter and the fuel/water separator filter incorporate top mounted bleeder valves to assist in the removal of air
from the fuel system.
Fuel Cutoff Solenoid An electrically operated fuel cutoff solenoid is mounted in the fuel metering pump. The so-
lenoid is normally open. A switch in the vehicle drivers compartment actuates the circuit to close the solenoid.
Closing the solenoid cuts off fuel delivery from the fuel metering pump and stops the engine. A manually operated
override shutoff is provided to permit stopping the engine in the event of an electrical failure.
MANIFOLD AIR INDUCTION AND HEATER SYSTEM
Turbosupercharger Assemblies Exhaust gas--driven turbosupercharger assemblies (Figure 1--4), one for each
bank of cylinders, are mounted on each side of the engine, at the rear. The turbosuperchargers increase the pres-
sure of the intake air thereby delivering a higher density air to the cylinders as compared with a non--supercharged
engine. This higher density air, with a proper fuel flow, increases engine power.
Intake Manifold Heater
The intake manifold (Figure 1--1), which distributes induction air to each bank of cylinders, is equipped with an elec-
trically--operated flame--type intake manifold heater (Figure 1--10). The heater is provided as an aid for cold weath-
er starting and cold weather operations. Operation of the heater switch (in the vehicle operators compartment)
energizes the manifold heater fuel solenoid valve, the heater ignition unit, and spark plug for each heater simulta-
neously. Fuel is hand--pumped through the manifold heater fuel filter and fuel solenoid valve and sprayed into the
intake manifold. The fuel is ignited by the spark plug and burns in the intake manifold as the engine is cranking,
and the flame heats the incoming air. This flame--heated air and the products of combustion are fed directly into
the cylinders with little heat loss. This results in an immediate engine response, and assures complete combustion
at low engine rpm and at no--load operating conditions with low ambient temperature.