828817 Mercury GROMMET

Illustration 1 g00849199
Diagram of the basic fuel system (typical example) (1) Fuel injection nozzles (2) Fuel return line from fuel injection nozzles (3) Air inlet heater (4) Fuel return line from fuel filter (5) Fuel return line from fuel injection pump (6) Supply line (7) Fuel filter (8) Fuel transfer pump (9) Water separator (10) Fuel injection pump (11) High-pressure fuel lines (12) Fuel tankWhen the engine is cranking, the fuel is pulled from the fuel tank (12) through the water separator (9) by the fuel transfer pump (8) . When the fuel goes through the water separator, any water in the fuel will go to the bottom of the bowl. The fuel transfer pump sends the fuel at a low pressure to the fuel filter (7) . From the fuel filter, the fuel goes through the supply line (6) to the fuel injection pump (10) .The fuel injection pump sends fuel through the high-pressure fuel lines (11) to each of the fuel injection nozzles (1) . The fuel injection nozzle sprays fuel into the cylinder. Fuel which is not used by the fuel injection pump goes through the fuel return line (5) to the inlet side of the fuel filter (7) . Fuel which is not used by the fuel injection nozzles flows through the fuel return line (2) to the top of the fuel filter, back to the fuel tank (12) , and through the fuel return line (4) .The fuel injection pump needs fuel for lubrication. The precision parts of the pump are easily damaged. For this reason, the engine must not be started until the fuel injection pump is full of fuel that is free of air.The system must be primed when any part of the system is drained of fuel. The following list contains examples of both service and repairs when you must prime the system:
The fuel filter is changed.
The fuel line is removed.
The fuel injection pump is removed.Fuel System Components
Illustration 2 g00296942
Fuel system components (left side) (1) Fuel injection nozzle (2) Fuel return line from fuel injection nozzles (3) High-pressure fuel lines (4) Fuel filter (5) Supply line (6) Fuel return line from fuel injection pump (7) Fuel injection pump
Illustration 3 g00296945
Fuel system components (right side) (8) Air inlet heater (9) Fuel supply line (10) Fuel transfer pumpThere is a small filter screen in the fuel transfer pump (10) . The pump has a lever which is manually operated in order to remove the air from the fuel system. In order to release air from the system, the orifice in the cover of the fuel filter (4) is in the inlet side of the filter. The orifice is connected to the fuel tank by the fuel return line from the fuel filter.The air inlet heater is an electrically operated device. The air inlet heater ignites a controlled amount of diesel fuel in the inlet manifold in order to heat the inlet air. A heater coil in the air inlet heater expands a delivery valve holder in order to allow the fuel to flow into the heater. The fuel is ignited by the hot coil. The combustion heats the air which passes through the air inlet manifold when the starter motor is operated.The air inlet heater (8) is installed in the inlet manifold. The air inlet heater is controlled by a remote mounted control switch.Note: If there is no fuel flow through the valve body of the air inlet heater, the fuel injection pump could be damaged. The fuel supply line to the heater must also be free of air in order to prevent damage. An air inlet heater that is damaged will allow the fuel to drain into the inlet manifold when the engine is running. This condition could cause exhaust smoke. Excessive fuel could also cause an overspeed condition.Fuel Injection Nozzles For Type 1 Engines and 9RM
Note: For a complete description of Type 1 and Type 2 engines, refer to the Systems Operation, Testing and Adjusting Module, "Engine Design" for more information.
Illustration 4 g00874781
Fuel injection nozzle (typical example) (1) Fuel inlet (2) Cap nut (3) Fuel return (4) Pressure adjustment screw (5) Spring (6) Nozzle body (7) Spindle for spring (8) Retaining nut for fuel injection nozzle (9) Needle valve (10) Nozzle tip (11) Orifices (12) Seat washerFuel flows under high pressure from the fuel injection pump through the hole in the fuel inlet (1) . The fuel then goes around the needle valve (9) which fills the inside of the nozzle tip (10) with fuel. The pressurized fuel pushes the needle valve and the spring (5) for the pressure adjustment screw. When the force of the fuel pressure is greater than the force of the spring, the needle valve (9) will lift up. When the needle valve opens, fuel under high pressure will go through the orifices (11) into the cylinder.When the fuel is sent to the cylinder, the force of the fuel pressure in the nozzle body will decrease. The force of the spring (5) will then be more than the force of the fuel pressure in the nozzle body. The needle valve (9) will move quickly to the closed position. Needle valve (9) has a close fit with the inside of the nozzle. The close fit makes a positive seal for the valve.When the fuel is sent to the cylinder, a small quantity of fuel will leak past the valve guide. This fuel lubricates the moving parts of the fuel injection nozzle. This fuel then goes through a passage in the nozzle body (6) to the fuel return (3) . This excess fuel is returned to the fuel tank.Fuel Injection Nozzles For Type 2 Engines and 7BJ
Note: For a complete description of Type 1 and Type 2 engines, refer to the Systems Operation, Testing and Adjusting Module, "Engine Design" for more information.
Illustration 5 g00874780
Fuel injection nozzle (typical example) (1) Fuel inlet (2) Fuel return line (3) Nozzle holder (4) Nozzle tip (5) Seat washer (6) OrificesEach fuel injection nozzle is fastened to the