THEORY OF OPERATION
ENGINE COMPONENTS (Continued)
Fuel Purge System:
A manually operated purge pump is provided in the
vehicle operator's compartment and is used to clear the
engine main fuel system and flame heater system of air,
and fill them 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 then to the
vehicle fuel tanks. Constant bleed orifices in the primary fuel filter and automatic water drain
in the fuel/ water separator filter remove water from the system.
Fuel Return Check Valve:
A fuel return check valve is installed between
the fuel injection pump fuel return outlet and
the fuel return hose assembly. The valve
prevents fuel flowing back to the injection
pump when the fuel supply is closed.
Fuel Supply Pump:
The engine driven fuel supply pump receives
fuel after it has been routed through the
backflow valve and the primary filter. It
supplies the fuel injection pump with a
uniform delivery pressure of 40 to 60 psi
maintained by an internal relief valve.
Engine Model 2DR uses a different supply
2DA & 2CA
pump from that which Models 2CA and 2DA
use. However, both are vane-type pumps
with a built-in bypass valve that allows fuel
to bypass during purging.
The fuel supply pump used on engine
Model 2DR rotates in an opposite direction
from the one used on Models 2CA and 2DA.
Therefore, they are not interchangeable.
WP 0004 00-21