0303951 JOHNSON SCREW, Pinion

Illustration 1 g01413929
Typical example
(1) Fuel tank
(2) Hand primer
(3) Sediment/water trap
(4) Fuel priming pump
(5) Fuel filter
(6) Fuel injection pump
(7) Fuel injectors
(8) Fuel return line from the fuel injection pump and the fuel injectors to the fuel tankWhen the engine is cranking, the fuel is pulled from the fuel tank (1) by the fuel priming pump (4). An optional sediment/water trap (3) may be installed between the fuel tank (1) and the fuel priming pump (4). The optional sediment/water trap has an inline style filter. If the optional sediment/water trap is installed, refer to Operation and Maintenance Manual for more information. The fuel priming pump forces the fuel through the fuel filter (5) to the fuel injection pump (6).The fuel filter (5) can also function as a water separator. The fuel filter can be drained through a valve that is located at the bottom of the filter housing.The fuel injection pump sends fuel at high pressure to each fuel injector nozzle (6). The fuel injector nozzle sprays fuel into a precombustion chamber which slows the rate of combustion in the cylinder. The following items will result from reducing the rate of fuel combustion: prevention of engine knock, reduction of noise and reduction of emissions.
Illustration 2 g00468241
Phases of operation of the fuel injection nozzle
(A) Closed valve
(B) Open valve
(C) Fully open valveThe fuel injection nozzle injects fuel into the precombustion chamber at different angles during two phases. Most of the fuel is injected when the valve is fully open (C). This process is called indirect fuel injection. The results are more even combustion and complete combustion of the fuel at a reduced temperature. Improved fuel combustion will increase power output while reducing emissions and reducing fuel consumption.Excess fuel from the fuel injection nozzles and the fuel injection pump flows through fuel return line (7) and back to the fuel tank (1). The excess fuel aids the cooling of the fuel injection nozzles. Also, the fuel return line removes any air that is trapped in the fuel injection nozzles and the fuel injection pump.The fuel injection pump needs fuel for lubrication. If the precision parts of the pump are not adequately lubricated, the components may be easily damaged. 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 low-pressure fuel line is removed.
The fuel injection pump is removed.
The fuel injection nozzles are removed.
The fuel tank is drained.
A leak exists in the low-pressure side of the fuel system.To release air from the fuel injection pump and the fuel injection nozzles, refer to Systems Operation, Testing, and Adjusting, "Fuel System - Prime".Governor
The fuel rack is connected to the linkage, which controls the fuel injection pump. This linkage is located in the timing case (Front Housing).These engines have a mechanical governor to control engine speed. The governor operates for all engine rpm. The governor weight assembly is installed on the front of the gear of the camshaft. The other components of the governor are installed in the front housing.
Illustration 3 g01374121
Governor control mechanism in the front housing without a BCD
(1) Connection for the linkage to the fuel injection pump
(2) Control lever
(3) Lever return spring
(4) Governor adjustment screw
(5) Arm
(6) Start spring
Illustration 4 g01384576
Governor control mechanism in the front housing with a BCD
(1) Connection for the linkage to the fuel injection pump
(2) Control lever
(3) Governor main spring
(4) Angleich
(5) Governor lever
(6) Start springThe movement of the governor weight assembly is transferred to the fuel rack on the fuel injection pump by the control lever (2), the governor lever (5), and the linkage to the fuel injection pump. The governor main spring (3) connects the governor lever to the control lever. The governor main spring controls the movement of the governor weight assembly on the camshaft. When the angle of the control lever changes, the tension on the governor main spring changes. This action controls the linkage to the fuel rack on the fuel injection pump, which controls the engine rpm.The maximum fuel adjustment screw is mounted in the front housing. This adjustment regulates the fuel injection at high engine rpm. This adjustment should only be made by personnel with the correct training.The fuel injection pump timing, the low idle, and the high idle are preset at the factory. Adjustments to the pump timing and idle rpm should only be made by personnel that have had the correct training. The timing for the fuel injection pump should only change if the camshaft or the cylinder block are replaced. The fuel injection pump timing should not change if the fuel injection pump is reinstalled with a shim that is the same size.The fuel rack automatically returns to the excess fuel position when the engine is stopped. The excess fuel position aids the cold starting of the engine.A spring connects the linkage to the fuel injection pump and mechanical stop control (2). When the engine is first started, the spring automatically increases the fuel flow to the cylinders.Boost Compensation Device for Turbocharged Engines (if equipped)
Illustration 5 g01412342
Boost Compensation Device (BCD)
(1) Adjustment screw
(2) Diaphragm piston
(3) Stopper
(4) Intake manifold pressure inlet
(5) Governor leverIf equipped, the Boost Compensation Device (BCD) can be installed on turbocharged engines. The BCD prevents overfuelling and the production of black smoke during acceleration from low idle.When the engine is accelerated from a low rpm, the governor lever (5) on the fuel rack comes into contact with the BCD fuel stopper (3) to prevent excessive movement of the governor lever. This prevents overfuelling.As the engine rpm increases, the increased intake manifold pressure is felt on the diaphragm in the BCD. As the BCD fuel stopper is moved by the diaphragm piston, the governor lever is allowed to operate over the full range.Fuel Injection Pump
Illustration 6 g00746909
Fuel injection pump (typical example)
(1) Fuel line to t