861844 Mercruiser O-RING

Illustration 1 g03347416
Fuel system components (1) Fuel injectors (left side) (2) Fuel rail pressure sensor (3) Return line for injector bypass fuel (4) High-pressure fuel pump (5) Fuel control valve and controller (6) Filter for high-pressure filter (7) Filter for high pressure fuel line (8) Fuel injectors (right side) (9) Temperature sensor for the low-pressure fuel (10) Unfiltered fuel pressure sensor (11) Filtered fuel pressure sensor (12) Test port for outer wall leakage collection (13) Temperature sensor for the high-pressure fuelThe fuel system for this engine incorporates a low-pressure fuel system and a high-pressure fuel system into the engine design.The low-pressure fuel system is used to transfer fuel from the fuel tank to the high-pressure fuel pump. During the transfer of fuel, water is removed from the fuel. Also, the fuel is filtered. The system incorporates a mechanical fuel transfer pump that is used to transfer fuel during engine operation. An electric fuel priming pump is used as a booster pump to increase fuel pressure in the system during engine starting. The fuel priming pump is also used to prime the low-pressure fuel system after the fuel filters are changed.The high-pressure fuel system pressurizes the fuel prior to injection. The fuel is transferred to the injectors through double wall fuel lines. The fuel injectors are used to produce atomized fuel during the fuel injection cycle. Flow limiters are used to limit the total flow of fuel to the injector to a preset level. Also, if an injector tip fails, the flow limiters will prevent the cylinder from filling with fuel. The fuel system is made up of the following components:
Low-pressure fuel lines
Primary fuel filter/water separator
Advanced efficiency secondary fuel filter
Mechanically driven fuel transfer pump
Electric fuel priming pump
High-pressure fuel pump and fuel control valve
In-line high-pressure fuel filter
Double wall fuel lines
High-pressure fuel injectors
Electronic control system componentsThese fuel system components form the design of these three engine subsystems:
Low-pressure fuel system
High-pressure fuel system
Electronic control system for fuel deliveryLow Pressure Fuel System
Illustration 2 g03347426
Schematic of the low-pressure fuel system (typical configuration) (16) Secondary fuel filters (17) Tertiary filter (18) High-pressure fuel system (19) Pressure regulator (low-pressure fuel) (20) Electric fuel priming pump (21) Vent cap for the fuel tank (22) Check valve (high-pressure fuel) (23) Check valve (outer wall leakage) (24) Mechanical fuel transfer pump (25) Fuel tankThe fuel is drawn from fuel tank (26) to the primary filter/water separator (25). The fuel tank uses vent cap (21) to vent off excess pressure for the fuel tank. The fuel is drawn into mechanical fuel transfer pump (24) and electric fuel priming pump (20). The electric fuel priming pump is energized during engine starting. Also, the electric priming pump can be used for priming the fuel system. The low-pressure pumps 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 mechanical fuel transfer pump pressurizes the low-pressure fuel system to a gauge pressure of 725 to 795 kPa (105 to 115 psi).The fuel then flows through secondary fuel filters (16) and tertiary filter (17). After the fuel has been filtered, the fuel flows into the high-pressure fuel system (18). The flow that is not used by the high-pressure fuel system is sent back to the fuel tank through pressure regulator (19). The pressure regulator is used to maintain the pressure in the low-pressure fuel system to a gauge pressure fo 725 to 795 kPa (105 to 115 psi). Check valves (22) and (23) are used to prevent fuel from draining from the high-pressure fuel system.Note: The number of fuel filters for the fuel system will vary by the engine application. A fuel cooler may be used on your application. The location of the fuel cooler depends on the application of the engine.High Pressure Fuel System
Illustration 3 g02476137
(27) Fuel lines for fuel return flow from injectors (28) High-pressure fuel line (29) Outer wall for high-pressure fuel leak collection (30) Flow limiter valve (31) Fuel injectors (32) Low-pressure fuel system (33) Fuel control valve (34) High-pressure fuel pump (35) In-line high-pressure fuel filter (36) Pressure relief valve for the high-pressure fuel systemFuel flows from low-pressure fuel system (32) to high-pressure fuel pump (34). The high-pressure fuel pump pressurizes the fuel. The pressure that is generated by the pump is regulated by fuel control valve (33). The fuel control valve regulates the pressure by restricting the amount of fuel that is allowed to enter the intake of the pump. The high-pressure fuel system is designed to operate at a nominal fuel pressure of 180 MPa (26,100 psi). Pressure relief valve (PRV) (36) is located in the monoblock that is at the rear of the high-pressure fuel pump. The PRV used to limit the pressure within the high-pressure fuel system to a maximum pressure of 205 MPa (29700 psi).The high-pressure fuel flows from the pump and the fuel is filtered by in-line high-pressure fuel filter (35). The high-pressure fuel then enters high-pressure fuel lines (double wall fuel line) (28) to fuel injectors (31). A small amount of fuel return flow that is expected returns to the tank through fuel lines (27). Flow limiter valve (30) limits the maximum flow of fuel to each injector.Note: Fuel leakage into the outer wall of the double wall fuel lines is considered to be a leak in the high-pressure fuel system. If leakage into the outer wall is identified, perform the necessary repairs. Refer to Testing and Adjusting, "Fuel Rail Leakage - Check", for information related to checking the high-pressure fuel system for leakage.Electronic Control System for Fuel Delivery
Fuel delivery is controlled by the Electronic Control Module (ECM) and various electric components. The following components are used by the ECM to provide the correct fuel delivery for the engine:
Electric fuel priming pump
Engine speed/timing sensors
Fuel control valve
Fuel injector solenoids
Pressure sensors
Temperature sensorsThe ECM receives data that is related to the current engine operating conditions from the various electronic components. The ECM utilizes this data in order to calculate the correct injection timing