804111 Mercury PLUG

Illustration 1 g06138139
Fuel system components (typical right side engine view)
(1) Fuel injectors (left side)
(2) Fuel rail pressure sensor
(3) Fuel control valve
(4) Electric fuel priming pump
(5) Fuel injectors (right side)
(6) Filtered fuel pressure sensor
(7) Temperature sensor for the low-pressure fuel
(8) Manual switch for the electric fuel priming pump
(9) Pressure sensor at the inlet of the fuel priming pump
(10) Temperature sensor for the high-pressure fuel
(11) Unfiltered fuel pressure sensor
(12) Block assembly that contains the in-line high-pressure fuel filter
(13) Clean Fuel ModuleThe 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 by the primary filters on the CFM (if equipped) and secondary and tertiary filters on the engine. 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 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.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
Clean Fuel Module (if equipped)
High-pressure fuel pump and fuel control valve
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 and High-Pressure Fuel System
Illustration 2 g06138296
Low-Pressure Fuel System and High-pressure Fuel system
(15) Outer wall for high-pressure leak collection
(16) Fuel injector
(17) High-pressure fuel lines
(18) Injector bypass
(19) Fuel lines for fuel return flow
(20) Pressure regulator
(21) Orifice
(22) Check valve for fuel return
(23) Fuel tank
(24) Primary fuel filters
(25) Priming pump
(26) Transfer pump
(27) Secondary fuel filters
(28) Tertiary fuel filter
(29) High-pressure fuel pump
(30) Clean Fuel ModuleLow-Pressure Fuel System
The fuel flows from fuel tank (23) to the mechanical fuel transfer pump (26) and electric fuel priming pump (25). The fuel is drawn through primary filter/water separator (24) prior to being pressurized by the fuel pumps. 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) to open the check valve in the high-pressure fuel pump during engine starting.The fuel then flows through secondary fuel filters (27). After flowing through the secondary fuel filters, the fuel flows into pressure regulator (20). The flow that is not used by high-pressure fuel system is sent back to the inlet of the fuel transfer pump (26). Orifice (21) removes any entrained air from the fuel and returns the entrained air back to the fuel tank. Fuel that does not pass through the pressure regulator then flows through the tertiary fuel filter (28). Only the fuel consumed by the high-pressure fuel pump will pass through the tertiary fuel filter (28). The check valve (22) on the return to the fuel tank line prevents backflow of fuel from fuel tank.Note: The number of fuel filters for the fuel system will vary by the engine application. The location of the fuel cooler depends on the application of the engine.Clean Fuel Module (If Equipped)
Illustration 3 g06138305
Schematic of the low-pressure fuel system equipped with the clean fuel module (typical configuration)
(23) Fuel tank
(24) Primary fuel filters
(25) Priming pump
(26) Fuel transfer pump
(30) Clean fuel module
(31) Ball valveThe clean fuel module (30) is an extra pump that pushes fuel from the fuel tank to the transfer/priming pumps on the engine. The clean fuel module uses kidney looping to circulate fuel continuously through the primary filters. A sensor has been added to monitor the fuel pressure out of the clean fuel module to more accurately measure fuel filter restriction.The clean fuel module performs the following:
Removes more particulates by recirculating fuel through the primary filters
Improves operation at low fuel tank levels
Helps with maintaining priming and with engine starting
Low pressure (instead of suction) enhances the ability to detect leaks in the fuel systemHigh-Pressure Fuel system
Fuel flows from low-pressure fuel system to high-pressure fuel pump (29). The high-pressure fuel pump pressurizes the fuel. The pressure that is generated by the pump is regulated by fuel control valve. The fuel control valve regulates the pressure by restricting the amount of fuel that is allowed to enter the intake of the pump. A relief valve that is internal to the high-pressure fuel pump limits the maximum fuel pressure that is generated by the pump to approximately 205 MPa (30,000 psi).The high-pressure fuel flows from the pump and is filtered by in-line high-pressure fuel filter. The high-pressure fuel then enters high-pressure fuel lines (double wall fuel line) (17) and the fuel is delivered to fuel injectors (16). A small amount of fuel return flow that is expected in injector bypass is routed back directly to the inlet of secondary filters through injector bypass fuel lines (19). Flow limiter valves limit the maximum flow of fuel to each injector.Note: Fuel leakage into outer wall (15) 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