861791 Mercruiser RACE

Illustration 1 g06359883
Typical example
(1) Fuel filter/water separator
(2) Pressure regulator
(3) Fuel injection pump
(4) Fuel transfer pump
(5) Fuel manifold (rail)
(6) Pressure relief valve
(7) Electronic unit injectorFuel is drawn from the fuel tank through a 4 micron fuel filter and a water separator with an integrated electric fuel priming pump.The fuel flows from the fuel filter to a pressure regulator. A pressure regulator that is installed in the low-pressure fuel system controls the fuel pressure to the fuel injection pump. The pressure regulator regulates the fuel at a pressure of between 20 to 50 kPa (3 to 7 psi) when the engine is cranking until the engine speed is above 600 rpm.The fuel then flows to the fuel transfer pump. The fuel transfer pump is part of the fuel injection pump.At the fuel injection pump, the fuel is pumped at an increased pressure of up to 200 MPa (29000 psi) to the fuel manifold (rail). Fuel that is leak off from the electronic unit injectors flows to the return line.Fuel that has too high a pressure from the fuel manifold (rail) returns through the pressure relief valve to the return line.High-Pressure Fuel System
Illustration 2 g06148124
Typical example
(1) Fuel injection pump
(2) Fuel temperature sensor
(3) Suction control valve for the fuel injection pump
(4) Pressure relief valve
(5) Electronic unit injector
(6) Fuel manifold (rail)
(7) Fuel pressure sensor
(8) Fuel transfer pumpThe fuel injection pump (1) feeds fuel to the high-pressure fuel manifold (rail) (6). The fuel is at a pressure of up to 200 MPa (29000 psi). A pressure sensor (7) in the high-pressure fuel manifold (rail) (6) monitors the fuel pressure in the high-pressure fuel manifold (rail) (6). The ECM controls a suction control valve (3) in the fuel injection pump (1) to maintain the actual pressure in the high-pressure fuel manifold (6) at the desired level. The high-pressure fuel is continuously available at each injector. The ECM determines the correct time for activation of the correct electronic unit injector (5) which allows fuel to be injected into the cylinder. The leakoff fuel from each injector passes through fuel lines that are connected to the top of the electronic unit injectors. From the top of the electronic unit injectors, the fuel line is connected to the pressure relief valve. A fuel line is connected to the pressure relief valve to return the leakoff fuel to the fuel tank.Components of the Fuel Injection System
The fuel injection system has the following mechanical components:
Fuel filter/water separator
Fuel injection pump
Fuel injectors
Fuel manifold
Pressure relief valve
Fuel pressure sensor
Fuel temperature sensorThe following list contains examples of both service and repairs when you must prime the system:
A fuel filter is changed.
A low-pressure fuel line is replaced.
The fuel injection pump is replaced.For the correct procedure to prime the fuel system, refer to Systems Operation, Testing and Adjusting, "Fuel System - Prime".Fuel Filter/Water Separator
Illustration 3 g06148166
Typical example
The fuel filter/water separator (1) provides a 4 micron filtration level. The fuel filter/water separator is supplied with water in fuel sensor (2).Fuel Pump Assembly
Illustration 4 g06148132
Typical example
The fuel pump assembly consists of a low-pressure transfer pump and a high-pressure fuel injection pump. The pump assembly is driven from a gear in the rear gear train at engine speed. The fuel injection pump (1) has two plungers that are driven by a camshaft. The fuel injection pump (1) delivers a volume of fuel two times for each revolution. The stroke of the plungers are fixed.The injector will use only part of the fuel that is delivered by each stroke of the pistons in the pump. The suction control valve (2) for the fuel injection pump (1) is controlled by the ECM. This maintains the fuel pressure in the fuel manifold (rail) at the correct level. A feature of the fuel injection pump (1) allows fuel to return to the tank continuously.The fuel temperature sensor (3) measures the temperature of the fuel. The ECM receives the signal from the fuel temperature sensor (3). The ECM calculates the volume of fuel.The fuel injection pump has the following operation:
Generation of high-pressure fuelThe fuel output of the fuel injection pump is controlled by the ECM in response to changes in the demand of fuel pressure.Shutoff
The engine shuts off by preventing the electronic unit injectors from injecting. The ECM then closes the suction control valve to prevent the pressure in the fuel manifold (rail) from increasing.Control
Illustration 5 g06359271
Typical example of the electrical control system for the fuel system
(1) Electronic Control Module (ECM)
(2) Throttle position sensor
(3) Turbocharger electronic wastegate
(4) Exhaust gas valve (NRS)
(5) Inlet throttle valve (NRS)
(6) Differential pressure sensor (NRS)
(7) Outlet temperature sensor (NRS)
(8) Inlet temperature sensor (NRS)
(9) Fuel pressure sensor
(10) Engine oil pressure switch
(11) Inlet manifold air pressure and temperature sensor
(12) Coolant temperature sensor
(13) Secondary speed/timing sensor
(14) Primary speed/timing sensor
(15) Fuel temperature sensor
(16) Fuel injection pump
(17) Suction control valve for the fuel injection pump
(18) Electronic unit injectorsThe ECM determines the quantity, timing, and pressure of the fuel to be injected into the fuel injector.The ECM uses input from the sensors on the engine. These sensors include the speed/timing sensors and the pressure sensors.The ECM controls the timing and the flow of fuel by actuating the injector solenoid.The amount of fuel is proportional to the duration of the signal to the injector solenoid.The ECM controls the fuel pressure by increasing or decreasing the flow of fuel from the fuel injection pump.Electronic Unit Injectors