SEGMENT G 5S0052 - 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 g06306363
(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 g06306368
(1) Fuel cooled injectors
(2) High-pressure system
(3) Back-pressure regulator
(4) Mono-block
(5) Fuel cooler application depended
(6) 100 µm strainer
(7) Fuel boost pump
(8) Primary filter
(9) Fuel tank
(10) Priming manual or solenoid valve
(11) Fuel Transfer Pump (FTP)
(12) FTP pressure relief valve
(13) Fuel filter group
(14) Anit-reverse flow check
(15) Starting valve
(16) System regulator
(17) 2.3 mm (0.091 inch) Cooling supply orificeAn electric off-engine boost pump supplies fuel from the tank to the on-engine mechanical fuel transfer pump. Fuel is drawn from the tank thru a strainer to protect the boost pump from debris. A bypass valve allows fuel to flow around the boost pump to prevent an engine shutdown in the event of a boost pump failure. Fuel then passes through the primary filters. The amount of filtered fuel required by the on-engine fuel system flows to the mechanical fuel transfer pump and the rest recirculates through the priming loop check valve and priming solenoid valve back to the boost pump inlet.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