815369 Volvo.Penta Spring

Illustration 1 g01114717
Fuel system schematic (typical example)
(1) Fuel supply line
(2) Unit injectors
(3) Fuel gallery (fuel manifold)
(4) Differential pressure switch (fuel)
(5) Fuel pressure sensor
(6) Fuel temperature sensor
(7) Fuel return line
(8) Pressure regulating valve
(9) Secondary fuel filter
(10) Fuel filter base
(11) Fuel transfer pump
(12) Electric fuel priming pump
(13) Pressure relief valve
(14) Primary fuel filter
(15) Fuel tank
(16) Fuel return line to tankThe fuel supply circuit is a conventional design for unit injector diesel engines. The system consists of the following major components that are used to deliver low pressure fuel to the unit injectors:Fuel tank - The fuel tank is used to store the fuel.Fuel priming pump - The fuel priming pump is used to evacuate the air from the fuel system. As the air is removed the system fills with fuel.Fuel filter - The fuel filter is used to remove abrasive material and contamination from the fuel system.Supply lines and return lines - Supply lines and return lines are used to deliver the fuel to the different components.The purpose of the low pressure fuel supply circuit is to supply fuel that has been filtered to the fuel injectors at a rate that is constant and a pressure that is constant. The fuel system is also utilized to cool components such as the ECM and the fuel injectors.Once the injectors receive the low pressure fuel, the fuel is pressurized again before the fuel is injected into the cylinder.The unit injector uses mechanical energy that is provided by the camshaft to achieve pressures that can be in excess of 200000 kPa (30000 psi).Control of the fuel delivery is managed by the engine's ECM. Data from several of the engine systems is collected by the ECM and processed in order to manage these aspects of fuel injection control:
Injection timing
Fuel injection timing advance
Injection duration
Engine cold mode statusThe mechanical electronic fuel system relies on a large amount of data from the other engine systems. The data that is collected by the ECM will be used in order to provide optimum performance of the engine.Low Pressure Fuel Supply Circuit
The flow of fuel through the system begins at fuel tank (15). Fuel is pulled from the tank by fuel transfer pump (11). The fuel is drawn through electric fuel priming pump (12). The electric fuel priming pump is used to remove air from the fuel system. While the air is removed, the system is filled with fuel. This assembly incorporates primary fuel filter (14) that removes large debris and water from the fuel. The primary fuel filter is a ten micron filter.The fuel transfer pump incorporates a check valve that will allow fuel to flow around the gears of the pump during priming of the fuel system. The fuel transfer pump also incorporates a pressure relief valve (13). The pressure relief valve is used in order to protect the fuel system from extreme pressure. The fuel transfer pump is engineered in order to produce an excess fuel flow throughout the fuel system. The excess fuel flow is used by the system to cool the fuel system components. The excess fuel flow also purges any air from the fuel system during operation. Air that can become trapped in the fuel system can cause cavitation that may damage the components of the unit injector.The fuel travels from the fuel transfer pump to fuel filter base (10). Fuel temperature sensor (6) is installed in the fuel filter base. This sensor detects the fuel temperature for the Electronic Control Module (ECM). An electrical signal that represents the fuel temperature is sent to the ECM for processing. Fuel pressure sensor (5) is also installed in the filter base. This sensor detects the fuel pressure for the ECM. An electrical signal that represents the fuel pressure is also sent to the ECM for processing. Differential pressure switch (4) is also installed in the fuel filter base. The differential pressure switch is used to alert the operator in case secondary fuel filter (9) becomes plugged. The secondary fuel filter is a two micron filter that removes abrasive material from the fuel. The fuel flows through a two micron fuel filter (6). The filtered fuel then flows out of the fuel filter base.Note: If a fuel cooled ECM is installed on the engine, the fuel is pumped into the ECM. The fuel travels through the cored passages of the housing of the ECM in order to cool the control module's electronics.Note: In some applications, a hand fuel priming pump may be located on the fuel filter base.The fuel is transfered by fuel supply lines (1) to fuel gallery (3) in the cylinder head. Only a portion of the fuel that is supplied to the fuel injectors is used for engine operation.The fuel that is unused by the engine is provided for cooling purposes. This unused fuel is discharged into the return passages of the fuel gallery. The fuel is returned to the fuel tank by fuel return lines (7) and (16). A continuous flow of fuel is experienced within the low pressure fuel system.Pressure regulating valve (8) is located in the fuel filter base. The pressure regulating valve allows the low pressure fuel system to maintain a constant pressure. A flow control orifice is also located in the fuel return. The flow control orifice maintains a system back pressure that is constant. The orifice allows the flow of fuel through the system to be constant. This prevents excessive heating of the fuel.Note: In some applications, the primary fuel filter and the secondary fuel filter are installed near the fuel supply tank. This location may be far from the engine. The pressure regulating valve will be located in a distribution block that is mounted on the engine.During engine operation, fuel injectors (2) receive fuel from the low pressure fuel system. The injector pressurizes the fuel to high pressure. The fuel is then injected into the cylinder. The excess fuel is returned to the tank. Refer to Systems Operation, "Unit Injector" for a complete explanation of the injection process.Fuel