Fuel Supply System

Fuel Supply System

Fuel Cut-off Control

During deceleration with the throttle valve closed, current to the fuel injectors is cut off to improve fuel economy at speeds over 1,100 rpm.

Fuel cut-off action also occurs when engine speed exceeds 6,000 rpm, regardless of the position of the throttle valve, to protect the engine from over-revving.

Fuel injector




The fuel injectors are a solenoid-actuated constant-stroke, pintleless-type consisting of a solenoid, plunger needle valve, and housing. When current is applied to the solenoid coil, the valve lifts up and pressurized fuel is injected. Because the needle valve lift and the fuel pressure are constant, the injection quantity is determined by the length of time that the valve is open (that is the duration the current is supplied to the solenoid coil). The fuel injector is sealed by an O-ring and seal ring at the top and bottom. These seals also reduce operating noise.

Fuel Pump Control

When the ignition is turned on, the ECM grounds the PGM-FI main relay which feeds current to the fuel pump for 2 seconds to pressurize the fuel system. With the engine running, the ECM grounds the PGM-FI main relay and feeds current to the fuel pump. When the engine is not running and the ignition is on, the ECM cuts ground to the PGM-FI main relay which cuts current to the fuel pump.

PGM-FI Main Relay

The PGM-FI main relay contains two separate relays. One is energized whenever the ignition is on which supplies battery voltage to the ECM, power to the fuel injectors, and power for the fuel cut relay. The fuel cut relay is energized to supply power to the fuel pump for 2 seconds when the ignition is switched ON (II), and when the engine is running.