91307-PK2-005 Honda O-RING (9.5X1.5) (Honda Code 2646149).

Illustration 1 g03877578
(1) Secondary fuel filter base with two 4 micron fuel filters (2) Common rail for fuel supply in cylinder head (3) Mechanical Electronic Unit Injector (MEUI) (4) Return fuel pressure regulator (5) Electric priming pump (6) Primary fuel filter base (7) Fuel tank (8) Primary fuel filter with water separator (9) Fuel transfer pump (10) Speed sensor (11) Pressure sensor (12) Battery (13) Temperature sensor (14) Timing calibration connector (15) Throttle position sensor (16) Level sensor (17) SAE J1939 Data Link (18) Electronic Control Module (ECM) (19) Warning lamp (20) Diagnostic lamp (21) Programmable outputs (22) PTO SET/RESUME switch (23) Power Take Off (PTO) ON/OFF switch (24) KeyswitchThe Electronic Unit Injector system consists of the following systems: the mechanical system and the electronic system. The mechanical system is made up of the low-pressure fuel supply system and the mechanical electronic unit injectors. The electronic system provides complete electronic control of all engine functions. The electronic control system consists of the following three types of components: input, control and output.There are six major components of the MEUI fuel system:
Mechanical electronic unit injectors
Fuel transfer pump
ECM
Sensors
Solenoids
CamshaftThe MEUI produces fuel injection pressures up to 207000 kPa (30000 psi). The MEUI also fires up to 19 times per second at rated speed. The fuel transfer pump supplies the injectors by drawing fuel from the tank and by pressurizing the system between 60 and 125 psi with an internal fuel pressure regulator. The ECM provides precise control to the fuel injector solenoids in order to achieve engine performance and compliance with emissions standards. Sensors are electronic devices which monitor the parameters of engine performance. The parameters of engine performance measure pressure, temperature, and speed. This information is sent to the ECM via a signal. Solenoids are electronic devices which use electronic currents from the ECM to change engine performance. An example of a solenoid is the Injector solenoid.Low Pressure Fuel System
Illustration 2 g03877599
(1) Secondary fuel filter (2) Common rail in cylinder head (3) Mechanical Electronic Unit Injector (MEUI) (4) Return fuel pressure regulator (5) Electric priming pump (6) Primary fuel filter base (7) Fuel tank (8) Primary fuel filter and water separator (9) Fuel transfer pumpThe low-pressure fuel system supplies fuel from the fuel tank to the injectors. The low-pressure fuel system has four basic functions:
Supply fuel for combustion
Supply fuel in order to cool the injectors.
Remove air from the fuel.
Warm the fuel in the fuel tank.The major parts in a low-pressure fuel system consist of the following components:
Fuel tank
Fuel transfer lines
Primary fuel filter or water separator
Fuel transfer pump
Secondary fuel filter
Fuel priming pump
Return fuel pressure regulatorThe mechanical electronic unit injectors, the fuel transfer pump, the ECM, sensors, and solenoids are part of the low-pressure fuel system.In the low pressure fuel system, the fuel is pulled from the fuel tank to the primary fuel filter or to the water separator. The primary fuel filter (9) removes debris from the fuel that is larger than 10 microns before the fuel flows into the fuel transfer pump (10). The fuel transfer pump is a gear pump that contains a pressure relief valve. The pressure relief valve opens at approximately 60 to 125 PSI. Fuel then flows from the outlet port of the fuel transfer pump to the secondary fuel filters. The 4 micron filters remove small abrasive contaminants from the fuel system, which can damage the unit injectors. The primary fuel filter base (6) contains an electric priming pump (5). The electric priming pump forces the air out of the system through the orifice on the regulator. Priming usually takes place after servicing the fuel system such as the changing of the fuel filter. When air is trapped in the fuel filters, the fuel lines, and other fuel system components, the engine could be difficult to start. This problem can also occur when the engine has not run for a long time. When there is air in the fuel line, the electric priming pump is activated by flipping a switch or by turning the start switch, in order to prime the system. The length of time for priming the fuel system depends on the size of the system, the length of the fuel line, and the size of the filter. The time that is needed in order to prime the fuel system is about 30 seconds. This value varies with different applications.The primary fuel filter base also contains a check valve that prevents reverse flow during priming.The return fuel pressure regulator (4) consists of a check valve that is spring loaded. When the engine is in the off position and the fuel pressure drops below 60 PSI, the check valve closes. The check valve closes in order to prevent the fuel in the cylinder head from draining back into the fuel tank. Retaining the fuel in the head maintains a supply of fuel for the injectors during start-up.The ECM controls major engine functions. Sensors are electronic devices that monitor the parameters of engine performance. The pressure sensor, the temperature sensor, and the speed sensor provide information to the ECM by a signal voltage. Actuators are electronic devices which use electrical currents from the ECM to change engine performance. An example of an actuator is an injector solenoid.Electronic Controls
The electronic control system provides complete electronic control of all engine functions. The electronic control system consists of the following three types of components: input, control and output. Sensors monitor engine operating conditions. This information is sent to the ECM. The ECM has three main functions. The ECM provides power for the engine electronics and monitors input signals from the engine sensors. The ECM also acts as a governor to control engine rpm. The ECM stores active faults, logged faults, and logged events. The Personality Module is the software in the ECM which contains the specific maps that define power, torque, and RPM of the engine. The ECM sends electrical current to the output components in order to control engine operation. The ECM has the following connectors: two 70 pin harness