NOZZLE AS-FUEL V 0R8242 - Caterpillar

The fuel system components form the design of these engine subsystems:
Low-Pressure Fuel System
High-Pressure Fuel System
Electronic Control System for Fuel DeliveryThese systems work together to ensure proper delivery of the fuel to each cylinder to achieve the required engine performance at all operation conditions.Low-Pressure Fuel System
Illustration 1 g06105490
(1) Injector Cooling Circuit Back-Pressure Regulator
Illustration 2 g06105499
(2) Filter Outlet Pressure Sensor
(3) Filter Inlet Pressure Sensor
(4) Starting Priority Valve
(5) System Regulator
(6) Fuel Rail Pressure Sensor
(7) Fuel Rail Temperature Sensor
(8) Mechanical Fuel Transfer Pump
(9) Fuel Transfer Pump Relief Valve
(10) Fuel Transfer Pump Inlet Pressure Sensor
(11) High-Pressure Fuel Pump (HPFP) Inlet Temperature Sensor
(12) Secondary Fuel FiltersThe basic function of the low-pressure fuel system is to provide fuel to the high-pressure fuel pump inlet at the:
Proper Pressure
Proper Temperature
Proper Cleanliness LevelThe fuel transfer pump (8) increases the fuel pressure for the transport through the secondary filters (12). The fuel transfer pump is equipped with a 950 kPa (138 psi) relief valve to prevent overpressure. Pressure sensors are at the inlet (3) and outlet (2) of the secondary filters to monitor filter condition. A temperature sensor (11) measures the temperature of the fuel exiting the secondary filter. The fuel then reaches the high-pressure pump inlet where a system pressure regulator (5) maintains the pressure at 650 kPa (95 psi) to 950 kPa (138 psi). During an engine start, a special starting priority valve (4) prevents flow to the injector cooling flow portion of the low-pressure fuel system until 250 kPa (36 psi) is reached. This action ensures adequate flow to the high-pressure pump at low engine cranking speeds. A certain amount of fuel flow bypasses the high-pressure pump and circulates through the injector cooling circuit. The injector cooling circuit back-pressure regulator (1) maintains the pressure in the injector cooling circuit at 350 kPa (51 psi). The unused fuel return then passes through the Mono-Block on the high-pressure pump and is returned back to the fuel tank. Low-Pressure Fuel System Schematic
Illustration 3 g06112982
(A) Fuel Cooled Injectors
(B) Double Wall Leakage Return
(C) Injector Cooling Circuit Back-Pressure Regulator
(D) Mono-Block
(E) Fuel Cooled High-Pressure Pump
(F) High-Pressure Pump Outlet
(G) 2.6 mm Injector Cooling Supply Orifice
(H) Anti-Reverse Flow Check
(I) Fuel Transfer Pump Pressure Relief Valve
(J) Low-Pressure Fuel System Regulator
(K) Secondary Fuel Filters
(L) Starting Priority ValveThe locomotive OEM system draws fuel from the tank and directs it through the primary fuel filters and fuel-water separator. The fuel is supplied to the mechanical fuel transfer pump. The fuel transfer pump must pressurize the fuel to approximately 250 kPa (36 psi) in order to open the check valve in the high-pressure fuel pump during engine starting. The fuel transfer pump provides a fuel pressure of 600 to 850 kPa (87 to 123 psi) to the secondary filter inlet. After the fuel has been filtered, the fuel flows into the high-pressure fuel system. Some of the flow that is not used by the high-pressure fuel system is used to cool the injectors. The rest is recirculated back to the fuel transfer pump inlet. The pressure regulator is used to maintain the pressure