3B2-00004-0 Tohatsu PISTON (0.5)

Illustration 1 g01343865
(1) Fuel filter housings (2) Fuel inlet line (3) Fuel injector (4) Fuel outlet line (5) Fuel return manifold (6) Fuel supply manifold (7) Check valve (8) Fuel filter change valve (9) Check valve (10) Fuel pressure control valve (11) Fuel supply line (12) Primary fuel filter (13) Check valve (14) Fuel transfer pump (15) Bypass valve (16) Check valve (17) Fuel priming pump (A) Fuel supply (B) Fuel returnFuel transfer pump (14) 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 (13) and a bypass valve (15). The check valve prevents fuel flow back through the fuel transfer pump. The bypass valve limits the maximum pressure of the fuel. The bypass 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 supply tank is pulled through the primary fuel filter (12) (if equipped) by the fuel transfer pump. From the fuel transfer pump, the fuel is then sent to the check valve (13) .The check valve prevents fuel flow back through the fuel transfer pump when a hand priming pump is used.The fuel transfer pump pushes the fuel through the following components:
Check valve (13)
Fuel filter change valve (8)
Fuel filter housings (1)
Fuel supply manifold (6)
Fuel inlet line (2)
Illustration 2 g01343891
Fuel flow through the cylinder head (3) Fuel injector (A) Fuel supply (B) Fuel returnA fuel inlet line (2) 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 (3). 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 (4) to the fuel return manifold (5). 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 (10). The fuel pressure control valve is located on the right side of the front housing. The fuel flows through the fuel pressure control valve. Then, the fuel flows back to the supply tank.The fuel pressure control valve regulates the pressure in the fuel system.The check valves prevent fuel flow back into the fuel filter housing when the fuel filters are changed. 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 (17) 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 (16) prevents fuel flow back through the hand priming pump when the engine is running.