- Low-Pressure Fuel System
- High-Pressure Fuel System
- Electronic Control System for Fuel Delivery
These systems work together to ensure proper delivery of the fuel to each cylinder to achieve the required engine performance at all operation conditions.
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| Illustration 1 | g06201711 |
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(1) Fuel Priming Pump
(2) Dry-Well Temperature Sensor (3) Fuel Transfer Pump (4) Low-Pressure Relief Valve (5) Fuel Temperature Sensor (6) Secondary Fuel Filters (7) Fuel Pressure Sensor (Unfiltered) (8) Fuel Pressure Sensor (Filtered) (9) Starting Priority Valve (10) Low-pressure Fuel System Pressure Regulator (11) Flow Control Valve (12) High-Pressure Relief Valve (13) High-Pressure Fuel Pressure Sensor (14) High-Pressure Junction Block (15) High-Pressure Fuel Pump (16) Double-Walled High-Pressure Fuel Lines (17) Injector Back-Pressure Regulator (18) Low-Pressure Injector Cooling/Leakage Lines (19) Fuel Injectors/Clamps (20) Accumulator Quill with Integrated Flow Limiter (21) Clean Fuel Module (CFM) (22) Primary Fuel Filters | |
Low-Pressure Fuel System Schematic
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| Illustration 2 | g06427958 |
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(1) Fuel Supply
(2) Clean Fuel Module (CFM) Pump (3) CFM Outlet Pressure Sensor (4) Primary Fuel Filters (5) Electric Fuel Priming Pump (6) Electric Fuel Priming Pump Bypass (7) Fuel Transfer Pump (FTP) Inlet Pressure Sensor (8) Fuel Transfer Pump (9) FTP Pressure Relief Valve (10) Fuel Pressure Sensor (Unfiltered) (11) Secondary Fuel Filters (12) Fuel Temperature Sensor (13) Fuel Pressure Sensor (Filtered) (14) Low-Pressure Fuel System Pressure Regulator (15) Secondary Fuel Filter Manifold (16) High-Pressure Pump (HPP) Supply (17) Starting Priority Valve (18) Injector Cooling Fuel Supply (19) High-Pressure Fuel Pump (20) Fuel injectors (21) Injector Cooling Circuit Pressure Regulator (22) High-Pressure Pump Fuel Cooling and Leakage Flow (23) Mono-Block (24) Double-Walled Return Line (25) Return to Fuel Tank Line (26) Fuel Cooler (if equipped) (27) Fuel Tank Vent Cap (28) Fuel Tank | |
The 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 Level
A fuel tank vent cap (27) is on fuel tank (28) to equalize air pressure. The fuel supply (1) is drawn from the fuel tank by the CFM (2) and then passes through the primary fuel filters (4).
The CFM assembly contains an electric fuel transfer pump, a fuel manifold with a pump outlet pressure sensor (3), and the primary fuel filters. The fuel then passes through the electric fuel priming pump (5). The priming pump is used after service or if the equipment has not been used recently.
When the fuel system has air trapped in the fuel filters, lines, and other fuel system components, the engine could experience difficulty starting. The electric fuel priming pump forces the air that is in the fuel system out through the injector cooling circuit and back to the tank.
Priming is required after servicing the fuel system such as changing the fuel filter. Priming is also recommended when the engine has not been used recently. Refer to the Operation and Maintenance Manual, Fuel System – Priming for details on the priming procedure.
The fuel is then drawn into the mechanical fuel transfer pump (8) that pressurizes the low-pressure fuel system from
The fuel flows through secondary fuel filters (11) and then is split by the secondary fuel filter manifold (15) to provide fuel to high-pressure pump (19) and injector cooling fuel supply circuit (18). Pressure sensors are at the inlet (unfiltered fuel pressure) (10) and outlet (fuel pressure) (13) of the secondary fuel filters to monitor filter condition. A fuel temperature sensor (12) measures the temperature of the fuel exiting the secondary filter.
During an engine start, starting priority valve (17) prevents flow to the injector cooling flow portion of the low-pressure fuel system until
The pressure is regulated by the low-pressure fuel system pressure regulator (14) and excess fuel flow is returned to the inlet of the fuel transfer pump.
The injector cooling circuit pressure regulator (21) maintains the pressure in the cooling rails above
Low-Pressure Fuel System Locations
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| Illustration 3 | g06174641 |
| (1) Injector Cooling Circuit Back-Pressure Regulator | |
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| Illustration 4 | g06428043 |
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(2) Filtered Fuel Pressure Sensor
(3) Unfiltered Fuel Pressure Sensor (4) Starting Priority Valve (5) Low-Pressure Fuel System Pressure Regulator (6) Fuel Transfer Pump (7) Fuel Transfer Pump Pressure Relief Valve (8) Fuel Transfer Pump Inlet Pressure Sensor (9) Fuel Temperature Sensor (10) Secondary Fuel Filters | |
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| Illustration 5 | g06199140 |
| (11) Clean Fuel Module located behind the chassis fuel tank | |
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| Illustration 6 | g06199138 |
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Fuel priming pump location may vary on different machine applications. (12) Fuel priming pump in chassis | |
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| Illustration 7 | g06185145 |
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(1) Injector
(2) Accumulator-Quill Tube (3) Line Support Clamps (4) High-Pressure Accumulator Lines (5) High-Pressure Fuel Pump to Junction Block High-Pressure Lines (6) High-Pressure Junction Block (7) High-Pressure Fuel Pump | |
The main components of this system are between the high-pressure fuel pump (7) and the injectors (1) as shown in Illustration 7:
- High-Pressure Fuel Pump to Junction Block High-Pressure Lines
- High-Pressure Junction Block
- Accumulator Quill Tubes
- Accumulator Quill to Accumulator Quill Fuel Injection Lines
The low-pressure fuel system provides fuel at the proper pressure, temperature, and cleanliness level to the high-pressure fuel pump. The high-pressure fuel pump pressurizes the fuel to the level required for the engine operating condition. System pressure in the high-pressure fuel system is controlled electronically via a fuel control valve, which regulates the amount of fuel that is allowed to enter the inlet of the pump. A pressure relief valve mounted on the high-pressure pump manifold mechanically limits the maximum fuel pressure in the system in the event of a malfunction.
High-Pressure fuel flows from a manifold on the high-pressure pump (7) to a high-pressure junction block (6), which distributes fuel to each engine cylinder bank via double-walled high-pressures accumulator lines (4). The double-wall serves to prevent the escape of any high-pressure fuel in the event of fuel leakage from the high-pressure system and therefore ensures safe containment of the fuel in the event of a high-pressure leak. The fuel is then transported through the high-pressure lines, through the accumulator quill tubes (2), and to the injectors (1). If leakage into the double-wall system occurs, the necessary repairs need to be performed as quickly as possible to prevent further damage to the high-pressure fuel system.
Fuel is transported to the accumulator-quill tubes via the double-walled accumulator lines. The accumulators contain an integral metallic filter to prevent debris from getting to the injectors. The accumulators also contain an integral flow limiting device that shuts off flow to the cylinder and prevents over fueling in the event of higher than expected fueling. Refer to Systems Operation, "Accumulator-Quill Tube", for information that is related to the operation of the accumulator-quill tubes.
The accumulator-quill tubes transport high-pressure fuel through each cylinder head directly to electronically controlled injectors that provide the proper injected fuel quantity and timing for the particular operating conditions. Refer to Systems Operation, "Fuel Injector" for information that is related to the operation of the fuel injectors.
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| Illustration 8 | g06176876 |
| (1) High-Pressure Fuel Pump | |
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| Illustration 9 | g06108778 |
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(2) Fuel Control Valve
(3) Temperature Sensor - Dry Well Port (4) High-Pressure Manifold (5) Rail Pressure Sensor Port (6) Low-Pressure Mono-Block (7) High-Pressure Pump Inlet (8) Magnetic Oil Drain Plug | |
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| Illustration 10 | g06112996 |
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(9) Double-Wall O-ring
(10) Rail Pressure Sensor | |
Note: The fuel rail pressure sensor is installed into the high-pressure fuel pump. This sensor has an integral crush washer and can only be used one time. Once the sensor is removed from the high-pressure pump, the previous sensor must be replaced with a new sensor.
The common rail fuel system high-pressure fuel pump on this engine is driven by an idler in the engine gear train. The flow of the low-pressure fuel into the high-pressure fuel pump is controlled by the fuel control valve (2). The fuel control valve controls how much fuel is allowed into the pump, which determines the pressure in the high-pressure fuel rail.
The high-pressure manifold mounted to the top of the pump contains the rail pressure sensor port, dry-well temperature sensor port, pressure relief valve, and the outlet port for high-pressure fuel. The pump also has a low-pressure mono-block (6) on the rear of the pump, which houses low-pressure fuel system valves and regulators and the high-pressure pump fuel inlet port.
Note: The high-pressure manifold (4) and the low-pressure mono-block (6) are not serviceable, should not be tampered with, and/or disassembled.
Note: If replacing the oil-lubricated high-pressure pump, the pump may contain residual oil from the performance testing completed at the factory. All oil and fuel connections and passages are plugged/capped with protective covers. Care should be taken to ensure removal of these protective covers upon installation.