TM-9-2815-220-24 Maintenance Manual for AVDS-1790-2CA AVDS-1790-DA and AVDS-1790-2DR Engines Download
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TM 9-2815-220-24 THEORY OF OPERATION 0004 00 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. PREHEAT PURGE OFF Check Valve 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: 2DA & 2CA 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 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. 2DR Supply Pump 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