922513-5655 Tohatsu SCREW

Illustration 1 g00673265
(1) Fuel Injectors. (2) Fuel pressure control valve. (3) Fuel cooler. (4) Secondary duplex fuel filters. (5) Day tank. (6) Fuel priming pump. (7) Primary fuel filter. (8) Fuel transfer pump. (9) Relief valve.
Fuel transfer pump (8) is located on the left rear side of the front housing. The fuel transfer pump is powered by a spur gear that is mounted on the engine oil pump drive gear.The fuel transfer pump has a check valve and a relief valve (9). The check valve prevents fuel flow back through the fuel transfer pump when the fuel priming pump is used. The relief valve limits the maximum pressure of the fuel. The relief valve will open the outlet side of the pump if the fuel pressure is greater than 725 kPa (105 psi). This helps to prevent damage to the fuel system components. The fuel system components can be damaged by too much pressure.Fuel from the day tank (5) is pulled through the primary fuel filter (7) by the fuel transfer pump. From the fuel transfer pump, the fuel is then sent to the secondary duplex fuel filter (4). The check valves of the secondary duplex filter prevent fuel flow back into the fuel filter housing when the fuel filters are changed. After the duplex fuel filter, the fuel is sent to the cylinder heads through the fuel oil's supply manifold.
Illustration 2 g00671980
Fuel Flow Through The Cylinder Head
(1) Fuel Injector. (C) Fuel return. (D) Fuel supply.
A fuel inlet line is located on the right side of each cylinder head. A drilled passage in the cylinder head directs the fuel to a circular chamber around each fuel injector (1). The chamber is made by the mating fit of the following components:
O-ring seals on the outside of the fuel injector
The bore for the fuel injector in the cylinder headOnly part of the fuel is used for injection. The remaining fuel flows through the chamber to a drilled passage on the left side of the cylinder head. This passage is connected by a fuel outlet line to the fuel return manifold. This constant flow of fuel around the fuel injectors helps to cool the fuel injectors.The fuel flows through the fuel return manifold to fuel pressure control valve (2). The fuel pressure control valve is located on the right side of the front housing. The fuel pressure control valve keeps the pressure in the fuel system at 430 to 670 kPa (62 to 97 psi). The fuel flows through the fuel pressure control valve to the fuel cooler (3). In the fuel cooler, the fuel is cooled by sea water in a plate type heat exchanger. After the fuel cooler, the fuel is sent back to the day tank.The system is also equipped with a fuel priming pump (6). It will not be necessary to use a priming pump to force air from the fuel system when the filters are changed. The priming pump must be used when the fuel lines are dry. For example, use the priming pump after an overhaul or other major fuel system maintenance. A check valve prevents fuel flow back through the hand priming pump when the engine is running.