0388272 JOHNSON CARBURETOR ASSEMBLY

Illustration 1 g03790131
Typical example
(1) In-line fuel filter (if equipped)
(2) Electric transfer pump (if equipped)
(3) Primary fuel filter (if equipped)
(4) Inlet pressure regulator
(5) Fuel injection pump
(6) Fuel manifold (rail)
(7) Pressure relief valve
(8) Electronic unit injector
(A) Fuel tank Fuel is drawn from the fuel tank through an in-line fuel filter to an external electric transfer pump. The fuel then flows to the 4 micron primary fuel filter and a water separator.A pressure regulator that is installed in the low-pressure fuel system controls the fuel pressure to the fuel injection pump.Note: There is a separate fuel return line from the pressure regulator to the fuel tank.From the primary fuel filter, the fuel flows to the fuel injection pump. The fuel is pumped at an increased pressure of 200 MPa (29000 psi) to the fuel manifold (rail).Fuel that has too high a pressure from the fuel manifold (rail) returns through the pressure relief valve to the return line. Fuel that is leak off from the electronic unit injectors flows to the return line. The fuel may then flow through an optional fuel cooler on the way back to the fuel tank.High Pressure Fuel System
Illustration 2 g03789648
Typical example
(1) Electronic unit injector
(2) Fuel manifold (rail)
(3) Fuel pressure sensor
(4) Fuel injection pump
(5) Suction control valve for the fuel injection pump
(6) Fuel temperature sensor
(7) Pressure relief valve The fuel injection pump (4) feeds fuel to the high-pressure fuel manifold (rail) (2). The fuel is at a pressure of 200 MPa (29000 psi). A pressure sensor (6) in the high-pressure fuel manifold (rail) (2) monitors the fuel pressure in the high-pressure fuel manifold (rail) (2). The ECM controls a suction control valve (5) in the fuel injection pump (4) in order to maintain the actual pressure in the high-pressure fuel manifold (2) 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 (1) which allows fuel to be injected into the cylinder. The leakoff fuel from each injector passes into a pipe that is connected to each injector. The pipe is connected to the pressure relief valve (7) and the fuel injection pump (4) in order to return the leakoff fuel to the fuel tank.Components of the Fuel Injection System
The fuel system has the following mechanical components:
Primary filter/water separator (if equipped)
Electric transfer pump
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.
The ECM is replaced.For the correct procedure to prime the fuel system, refer to Systems Operation, Testing and Adjusting, "Fuel System - Prime".Primary Filter/Water Separator (If equipped)
Illustration 3 g03799258
Typical example
Note: The primary filter/water separator is mounted on the application.The primary filter/water separator (1) is located between the electric transfer pump and the fuel injection pump. The primary filter/water separator (1) provides a 4 micron filtration level.The primary filter/ water separator may be supplied with water in fuel sensor (2).Fuel Pump Assembly
Illustration 4 g03789669
Typical example
The pump assembly is driven from a gear in the front timing case 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 g03790133
Typical example of the electrical control system for the fuel system
(1) Electronic Control Module (ECM)
(2) Boost pressure sensor
(3) Engine oil pressure switch
(4) Diesel Oxidation Catalyst (DOC) inlet temperature sensor
(5) Exhaust temperature sensor
(6) Inlet manifold air temperature sensor
(7) Coolant temperature sensor
(8) Secondary speed/timing sensor
(9) Primary speed/timing sensor
(10) Exhaust gas valve (NRS)
(11) Intake throttle valve (NRS)
(12) Fuel pressure sensor
(13) Fuel injection pump
(14) Fuel temperature sensor
(15) Suction control valve for the fuel injection pump
(16) Electronic unit injectors The ECM determines the quantity, timing, and pressure of the fuel in order to be injected into the fuel injector.The ECM uses input from the sensors on the engine. These sensors include the speed 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.Fuel Injectors