3B7-77085-1 Tohatsu BOLT, 12 - 20 P1.75

Illustration 1 g00987171
Flow diagram of the fuel system (1) Fuel injection nozzles (2) High-pressure fuel lines (3) Fuel return lines (4) Fuel injection pump (5) Fuel supply line (6) Return line to the fuel tank (7) Fuel transfer pump (8) Fuel filter/water separator (9) Fuel tankThe engine is equipped with an axial piston distributor injection pump that is mechanically governed.The axial piston distributor injection pump generates injection pressure for all cylinders in a single pump. The injection pump is responsible for the distribution of fuel to the fuel injection nozzles. The injection pressure is generated by an axially moving piston. The movement of the piston is parallel to the fuel injection pump shaft.When the engine is cranking, the fuel is pulled from fuel tank (9) through the primary fuel filter/water separator (8) by fuel transfer pump (7) . When the fuel passes through the water separator, any water in the fuel will go to the bottom of the bowl. From the fuel transfer pump, the fuel passes through fuel supply line (5) to fuel injection pump (4) .The fuel is drawn by an internal fuel transfer pump into the fuel injection pump. The fuel is drawn by an internal fuel transfer pump at a pressure of 48 to 83 kPa (7 to 12 psi). A portion of the fuel is routed through the pressure regulator assembly to the suction side of the fuel injection pump. The fuel that is under pressure from the fuel transfer pump flows to the interior of the pump housing. The pressurized fuel is routed to the pumping chamber. As the plunger rotates and as the plunger reciprocates, high-pressure fuel is routed through high-pressure fuel lines (2) to fuel injection nozzles (1) .The fuel injection nozzles spray atomized fuel into the cylinder. Excess fuel is routed through fuel return lines (3) and (6) and returned to the fuel tank.Routing excess fuel back to the fuel tank allows air in the fuel to flow back to the fuel tank through the fuel return line. The fuel that flows into the housing of the fuel injection pump performs the following functions:
Lubricate the internal components.
Cool the internal components.
Remove small air bubbles.The fuel injection pump needs fuel for lubrication. The precision parts of the pump are easily damaged. The engine must not be started until the fuel injection pump is full of fuel. The system must be primed when any part of the system is drained of fuel. The fuel system needs priming when a fuel filter is changed, and/or when a fuel line is removed, and/or when the fuel injection pump is replaced.Fuel Injection Pump
Illustration 2 g00992842
Components of the fuel injection pump (typical example) (1) Control lever (2) Flyweights (3) Screw for adjusting the full load setting (4) Drive shaft (5) Governor lever (6) Fuel shutoff solenoid (7) Head of the distributor (8) Control sleeve (9) Transfer pump (10) Holder for the rollers (11) Plunger (12) Cam (13) Timer (14) Plunger spring (15) Delivery valveThe fuel injection pump is a pressurized system that is enclosed. The pump sends the correct amount of fuel