16122 Mercury SCREW (SHORT)

Engine Design
Type ... Four Cylinder, Four StrokeCombustion System ... Direct InjectionNominal Bore ... 100 mm (3.937 in)Stroke ... 127 mm (5.00 in)Cubic Capacity ... 4 liters (243 cu in)Compression Ratio ... 16 to 1Number and Arrangement of Cylinders ... in-line, 4Firing Order ... 1-3-4-2Rotation of crankshaft (as seen from front of engine) ... ClockwiseRotation of camshaft (as seen from front of engine) ... ClockwiseThe left side and right side of engine are as seen from flywheel end. No. 1 cylinder is the front cylinder of the engine.Engine Serial Numbers
Engine Serial Number LocationThe engine serial number is located on the left side of the cylinder block.Fuel System
Basic Fuel System Diagram (Typical Example)
(1) Fuel injection nozzle. (2) Fuel return line. (3) Cold start heater (thermostart). (4) Fuel return line. (5) Fuel return line. (6) Fuel supply line. (7) Fuel filter. (8) Fuel lift pump. (9) Water separator. (10) Fuel injection pump. (11) High pressure fuel lines. (12) Fuel tank.When the engine is turning, fuel is pulled from fuel tank (12) through water separator (9) by fuel lift pump (8). When the fuel goes through the water separator, any water in the fuel will go to bottom of the bowl. The fuel lift pump sends the fuel at a low pressure to fuel filter (7). From the fuel filter, the fuel goes through fuel supply line (6) to fuel injection pump (10). The fuel injection pump sends fuel through high pressure fuel lines (11) to each fuel injection nozzle (1), and the fuel injection nozzle sprays fuel into the cylinder. Fuel not used by the fuel injection pump goes through fuel return line (5) to the inlet side of fuel filter (7).Leakage from the fuel injection nozzles flows through fuel return line (2) to the top of fuel filter (7) and back to fuel tank (12), through 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 injection pump is full of fuel that is free of air.The system must be primed any time any part of the system is drained of fuel. When the fuel filter is changed or a fuel line is removed, when the inspection cover on the fuel injection pump is removed for service or repair, the fuel system must be primed (air removed). See, Remove Air From Fuel System in Testing & Adjusting.There is a small screen in fuel lift pump (8). The pump also has a manual lever to prime the fuel system (remove the air). The orifice in the cover of fuel filter (7), to release air in the system, is in the inlet side of the filter. The orifice is connected to the fuel tank by fuel return line (4).Cold start heater (3) is installed in the inlet manifold. It is controlled by a remote mounted control switch.
Unless there is fuel flow through the valve body of the cold start heater, the unit could be damaged. The fuel supply line to it must also be free of air, or damage could result. A cold start heater, that is damaged, will let fuel drain into the inlet manifold when the engine is running and could cause exhaust smoke.
Fuel Injection Nozzle
Fuel Injection Nozzle
(1) Fuel return. (2) Cap nut. (3) Fuel inlet. (4) Pressure adjusting screw. (5) Pressure adjusting spring. (6) Body. (7) Spring spindle. (8) Nozzle retaining nut. (9) Needle valve. (10) Nozzle. (11) Orifices (four). (12) Sealing washer.Fuel, under high pressure from the fuel injection pump, goes through the hole in fuel inlet (3). The fuel then goes around needle valve (9), fills the inside of nozzle (10) with fuel and pushes against needle valve (9) and pressure adjusting spring (5). When the force made by the pressure of the fuel is more than the force of pressure adjusting spring (5), needle valve (9) will lift. When needle valve (9) lifts, fuel under high pressure will go through orifices (11) into the cylinder. When the fuel is sent to the cylinder, the force made by the pressure of the fuel in the nozzle body will become less. The force of pressure adjusting spring (5) will then be more than the force of the pressure of the fuel in the nozzle body. Needle valve (9) will move quickly to the closed position.Needle valve (9) has a close fit with the inside of the nozzle. This makes a positive seal for the valve.When the fuel is sent to the cylinder, a small quantity of fuel will leak by the valve guide. This fuel gives lubrication to the moving parts of the fuel injection nozzle. This fuel then goes through a leak off passage in body (6) to fuel return (1) to the fuel tank.
Fuel Injection Nozzle
(2) Cap nut. (6) Body. (8) Nozzle cap nut. (10) Nozzle.Fuel Injection Pump
Fuel Injection Pump Components
(1) Control lever. (2) Flyweights. (3) Full-load adjusting screw. (4) Drive shaft. (5) Governor lever. (6) Solenoid. (7) Distributor head. (8) Control sleeve. (9) Feed pump. (10) Roller holder. (11) Plunger. (12) Cam disk. (13) Timer. (14) Plunger spring. (15) Delivery valve.The fuel injection pump is a totally enclosed and pressurized system. The pump sends the correct amount of high pressure fuel through fuel injection nozzles, to individual cylinders at the correct time (near end of compression stroke). The fuel injection pump meters (measures) amount of fuel delivered to the fuel injection nozzles. This action controls engine speed by the governor setting or position of the accelerator or throttle control.The fuel lines to the fuel injection nozzles are equal lengths. This insures even pressure and correct injection timing at each fuel injection nozzle.During operation, extra fuel which is used as coolant and lubricant for pump parts that move is circulated through the pump housing and returned to the tank. Return lines also carry away any air trapped in the fuel injection nozzles or pump housing.
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