0323942 JOHNSON THRUST WASHER, Propeller shaft, rear

Illustration 1 g01155662
(1) Cylinder head
(2) Unit injector
(3) Fuel transfer pump
(4) Secondary fuel filter and priming pump
(5) Fuel tank
(6) Electronic Control Module (ECM)
(7) Primary fuel filter and water separator The 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 primary fuel 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 is used to remove abrasive material and contamination as small as two microns that could damage the injectors.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 that is constant and a pressure that is constant. The fuel system is also utilized to cool components such as the fuel injectors and the Electronic Control Module (ECM).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 engine's ECM. Data from several of the engine systems is collected by the ECM and processed in order to manage these aspects of fuel injection control:
Injection timing
Fuel injection timing advance
Injection duration
Engine cold mode status The 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 in order 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 is drawn through the primary fuel filter and water separator (7) from the fuel tank by fuel transfer pump (3). The fuel transfer pump incorporates a check valve that 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 in order to protect the fuel system from extreme pressure.The fuel transfer pump is designed in order 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.After leaving the fuel transfer pump, the fuel flows to the ECM (6) in order to cool the ECM. Next, the fuel flows to the secondary fuel filter and fuel priming pump (4). The fuel priming pump is located on the fuel filter base. The priming pump is a hand operated pump that directs the flow of fuel during the priming pump's operation. The secondary fuel filter is a two micron fuel filter. The fuel is filtered in order to remove small abrasive particles that will cause premature wear to fuel system components. The filtered fuel then flows out of the fuel filter and returns to the passages in the fuel filter base. Prior to exiting the fuel filter base, the fuel pressure and the fuel temperature are sampled by the fuel pressure sensor and by the fuel temperature sensor. The signals that are generated by the sensors are used by the ECM in order to monitor the condition of the engine components. This information is also used to adjust the fuel delivery of the engine in order to optimize efficiency.The fuel is then transferred by the fuel supply lines to the cylinder head (1). Only a portion of the fuel that is supplied to the fuel injectors is used for engine operation. This unused fuel is discharged into the return passages of the fuel gallery. The fuel is returned to the fuel tank by the fuel return lines. A continuous flow of fuel is experienced within the low-pressure fuel system.During engine operation, fuel injectors (2) receive fuel from the low-pressure fuel system. The injector pressurizes the fuel to high pressure. The fuel is then injected into the cylinder. The excess fuel is returned to the tank.A pressure regulating valve is located in the fuel return. The pressure regulating valve allows the low-pressure fuel system to maintain a constant pressure. A flow control orifice is also located in the fuel return. The flow control orifice maintains a system back pressure that is constant. The orifice allows the flow of fuel through the system to be constant. This prevents excessive heating of the fuel.Fuel Heaters
Fuel heaters prevent the waxing of the fuel, and the plugging of the fuel filters in cold weather. The engine does not dissipate enough heat in order to prevent waxing during cold-weather conditions. There are two types of fuel heaters that can be used: thermostatically controlled and self-adjusting. Heaters that are not thermostatically controlled can heat the fuel in excess of 65 °C (149 °F). High fuel temperatures can have the following effects:
Reduced engine efficiency
Fuel pump damage
Premature wearNote: Never use fuel heaters without some type of temperature regulator. Ensure that fuel heaters are turned OFF during warm-weather conditions.Fuel System Electronic Control Circuit
The fuel system is equipped with an electronically controlled, mechanically actuated unit injector in each cylinder. A solenoid on each injector controls the amount of fuel that is delivered by the injector. An ECM sends a signal to each injector solenoid in order to provide complete control of