15171-ZN4-000 Honda PIPE, BREATHER (Honda Code 5988415).

Illustration 1 g03665563
Fuel system components (typical right side engine view)
(1) Fuel injectors (left side)
(2) Secondary and tertiary fuel filter assemblies
(3) Fuel rail pressure sensor
(4) Temperature sensor for the low-pressure fuel
(5) Pressure sensor for filtered fuel
(6) Pressure sensor for filtered fuel (secondary ECM)
(7) Duplex fuel filter valve
(8) Pressure sensor for unfiltered fuel
(9) High-pressure fuel pump
(10) Fuel rail pressure sensor (secondary)
(11) Primary fuel control valve and controller
(12) Fuel injectors (right side)
(13) Fuel transfer pump
(14) Fuel pressure regulating valve
(15) High-pressure leak detection sensor
(16) Block assembly that contains the in-line high-pressure fuel filter
(17) Temperature sensor for the high-pressure fuel
(18) Fuel control valve and controller (secondary)
(19) Electric fuel priming pump The fuel system for this engine incorporates a low-pressure fuel system and a high-pressure fuel system.The low-pressure fuel system transfers fuel from the fuel tank to the high-pressure fuel pump. During the transfer of fuel, water is removed from the fuel and the fuel is filtered through a fuel/water separator. The system incorporates a mechanical fuel transfer pump that transfers fuel during engine operation. An electric fuel priming pump is used as a booster pump to increase fuel pressure in the system during engine starting. The fuel transfer pump pumps the fuel through secondary and tertiary fuel filters prior to reaching the high-pressure fuel pump.The high-pressure fuel system pressurizes the fuel prior to injection. The fuel is transferred to the injectors through double wall fuel lines. In the case of a leak, the double wall fuel lines provide containment of the high-pressure fuel. The fuel is filtered again between the high-pressure fuel pump and the injectors. For this application, a leak detection system detects fuel leaks from the high-pressure fuel system. The fuel injectors atomize fuel during the fuel injection cycle. Flow limiters limit the total flow of fuel to the injector to a preset level.The fuel system components form the design of these three engine subsystems:
Low-pressure fuel system
High-pressure fuel system
Electronic control system for fuel deliveryLow Pressure Fuel System
Illustration 2 g02431016
Schematic of the low-pressure fuel system (typical configuration)
(19) Valve for the duplex fuel filter
(20) Secondary fuel filters
(21) Tertiary filters
(22) High-pressure fuel system
(23) Pressure regulator
(24) Check valve
(25) Electric fuel priming pump
(26) Mechanical fuel transfer pump
(27) Primary filter/water separator
(28) Fuel tank The fuel flows from fuel tank (28) to mechanical fuel transfer pump (26) and electric fuel priming pump (25). The fuel is drawn through primary filter/water separator (27) prior to being pressurized by the fuel pumps. The electric fuel priming pump is energized during engine starting. Also, the electric priming pump can be used for priming the fuel system. The low-pressure pumps must pressurize the fuel to approximately 250 kPa (36 psi) in order to open the check valve in the high-pressure fuel pump during engine starting.
Illustration 3 g02432076
Valve control for the duplex fuel filter (front left side engine view)
The fuel then flows through valve assembly (19). The valve for the duplex fuel filter selects either of the two filters. The different positions of the valve allow for changing and priming one of the fuel filters while the engine is running. Secondary fuel filters (20) and tertiary filters (21) are of filter-in-filter design. This design performs in the same filtering capacity as a two filter system. After the fuel has been filtered, the fuel flows into pressure regulator (23). The flow that is not used by high-pressure fuel system (22) is sent back to the fuel tank through the pressure regulator. Check valve (24) prevents fuel from draining from the return lines of the low-pressure system.High Pressure Fuel System
Illustration 4 g02432216
(29) High-pressure fuel line
(30) Fuel lines for fuel return flow
(31) Flow limiter valve
(32) Fuel injectors
(33) Low-pressure fuel system
(34) Fuel control valve
(35) High-pressure fuel pump
(36) In-line high-pressure fuel filter
(37) Manifold for the leak detection sensor Fuel flows from low-pressure fuel system (33) to high-pressure fuel pump (35). The high-pressure fuel pump pressurizes the fuel. The pressure that is generated by the pump is regulated by fuel control valve (34). The fuel control valve regulates the pressure by restricting the amount of fuel that is allowed to enter the intake of the pump. A relief valve that is internal to the high-pressure fuel pump limits the maximum fuel pressure that is generated by the pump to approximately 205 MPa (30,000 psi). The high-pressure fuel flows from the pump and the fuel is filtered by in-line high-pressure fuel filter (36). The high-pressure fuel then enters high-pressure fuel lines (double wall fuel line) (29) and the fuel is delivered to fuel injectors (32). A small amount of fuel return flow that is expected returns to the tank through fuel lines (30). Flow limiter valve (31) limits the maximum flow of fuel to each injector.Note: Fuel leakage into the outer wall of the double wall fuel lines is considered to be a leak in the high-pressure fuel system. Manifold (37) is used to collect fuel leakage from the outer walls. A fluid sensor is installed into the manifold in order to send a signal to the Electronic Control Module (ECM) if a leak occurs. A diagnostic trouble code is generated if a leak is detected in the outer wall of the high-pressure fuel lines. If leakage into the outer wall is identified, perform the necessary repairs.Electronic Control System for Fuel Delivery
Fuel delivery is controlled by the ECM and various electric components. The following components are used by the ECM to provide the correct fuel delivery for the engine:
Electric fuel priming pump
Engine speed/timing sensors
Fuel control valve
Fuel injector solenoids
Pressure sensors
Temperature sensorsThe ECM receives data that is related to the current engine operating conditions from the various electronic components. The ECM utilizes this data in order to calculate the correct injection timing and injection duration. A throttle signal is also calculated for the fuel control valve. An injection signal is sent to the fuel injectors in order to provide fuel delivery to the engine.Refer to Systems Operation, "Fuel Injector" for information that is related to the operation of the fuel injectors.