888255T Mercury PLATE

Illustration 1 g06545085
Fuel system schematic
(1) Rocker arm
(2) Fuel injector solenoid connector
(3) Relief valve
(4) Fuel supply to head
(5) Secondary/tertiary fuel filter
(6) Fuel transfer pump
(7) Fuel tank
(9) Fuel injector nozzle
(9) Camshaft
(10) Primary fuel filter/water separatorThe fuel supply circuit is a conventional design for engines that use fuel injectors. The fuel supply circuit uses fuel transfer pump to deliver fuel from the fuel tank to the electronic fuel injectors. The transfer pump is a fixed displacement gear pump.The fuel flows then through a fuel filter before entering the fuel supply manifold. An electric fuel priming pump is located in parallel with the fuel transfer pump to fill the system. The system must be primed after the filter changes. The system must be primed after draining the fuel supply and return manifolds, when the fuel injectors are replaced.The fuel flows continuously from the fuel supply manifold through the fuel injectors. The fuel flows when either the supply or the fill port in the injector is not closed by the injector body assembly plunger. The fuel that is not injected into the cylinder is returned to the tank through the fuel return manifold.A pressure regulating valve is at the end of the fuel return manifold. The pressure regulating valve controls the entire fuel system pressure. The regulation provides proper filling of the fuel injectors.The electronically controlled mechanically actuated fuel injector system provides total electronic control of injection timing. The injection timing is varied to optimize the engines performance.The timing ring is part of the rear gear group. A signal is generated by the engine speed/timing sensor. This information is for detection of crankshaft position and for engine speed. Other information and these data allow the Electronic Control Module (ECM) to send a signal to the injector solenoids. The fuel injector solenoid is energized to begin fuel injection. The fuel injector solenoid is de-energized to end fuel injection. Refer to Systems Operation, "Fuel Injector".
Illustration 2 g06544774
Fuel system schematic
(1) Mechanical electronic unit injector
(2) Fuel pressure regulator manifold and check valve
(3) Fuel return line
(4) Tank breather filter
(5) Fuel tank
(6) Fuel supply line
(7) Primary fuel filters/water separators
(8) Fuel pressure sensor
(9) Electric fuel priming pump
(10) Fuel transfer pump
(11) Fuel pressure sensor
(12) Secondary/tertiary fuel filter
(13) Fuel temperature sensor
(14) Fuel pressure sensorThe 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 filters - The fuel/water separator is a 10 micron filter with a water separator. This filter is used to remove abrasive material and contamination from the fuel system that may be large enough to damage the fuel transfer pump. The secondary fuel filter, which is on the secondary fuel filter base, is used to remove abrasive material and contamination. As small as 4 microns that could damage the injectors. The tertiary fuel filter is on the secondary fuel filter base. The tertiary fuel filter is used to remove abrasive materials and contamination as small as 4 microns. A differential pressure switch is utilized on the secondary fuel filter base to indicate the life of the fuel filter.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 and a pressure that is constant. The fuel system is also utilized to cool components such as 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 Electronic Control Module (ECM) of the engine. Data from several of the engine systems is collected by the ECM and processed 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 to provide optimum performance of the engine.Low Pressure Fuel Supply Circuit
The flow of fuel through the system begins at fuel tank (5). Fuel that is drawn from the tank by the fuel transfer pump (10) is filtered through a fuel/water separator. The separator is a 10 micron filter with a water separator. Fuel flows from the filter to the fuel transfer pump. The fuel transfer pump incorporates a check valve. The fuel transfer pump 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. The pressure relief valve is used to protect the fuel system from extreme pressure.The fuel transfer pump is engineered 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 priming pump (9) is on the fuel/water separators base. The fuel filter base and fuel/water separator (7) also incorporate a siphon break. The siphon break prevents fuel from draining from the fuel system when the engine is not in operation. The priming pump is an electric pump that directs the flow of fuel during the priming pump operation. The fuel flows through a secondary fuel filter base which contains the following filters: secondary and tertiary. The secondary/tertiary filters (12) is a 4 micron fuel filter