Fuel System

The main components of the fuel system are the in-tank electric fuel pump, fuel filter, fuel pulsation damper, injector, cold start injector and pressure regulator.
The fuel, under high pressure supplied by the fuel pump, is sent through the fuel feed lines and fuel filter and delivery pipe where it is delivered to each injector. There it is injected to the inlet port of the engine under the control of the ECM. At cold engine start, the fuel is also injected into the surge tank from the cold start injector. In the delivery pipe, the fuel pressure is regulated at a constant, relative to intake manifold pressure by the pressure regulator which is incorporated in the delivery pipe. When the fuel pressure is approximately 37 psi higher than intake manifold pressure, the fuel flows out from the pressure regulator, through the fuel return line and back to the fuel tank. Also attached to the delivery pipe is a pulsation damper which dampens the fuel pulsation that occurs in the delivery pipe when the fuel is injected, so that the noise caused by the pulsation is reduced.

Fuel Pump
The electric fuel pump is an integral part of the fuel tank and its operation is controlled by the ECM. When in operation, it pumps fuel from the fuel tank and feeds is under pressure to the injector.
When power is supplied to the fuel pump by the ECM, the motor in the pump and the impeller both operate. This causes a pressure difference to occur between both sides of the impeller as there are many grooves around it. The fuel is then drawn through the inlet port and with its pressure increased, it is discharged through the outlet port. The fuel pump also has a relief valve to prevent and excessive rise of the discharge pressure and a check valve to retain some pressure in the fuel feed line, even when pump operation is stopped.

Fuel Filter
As the filter is located in the fuel line, exposed to high fuel pressure, a high fuel pressure type filter is used.
Fuel Pressure Regulator
The fuel pressure regulator keeps the fuel pressure applied to the injector at approximately 37 psi higher than that in the intake manifold at all times. When pressure increases above 37 psi, the fuel pushes the valve in the regulator open and excess fuel returns to the fuel tank through the return pipe.

Fuel Injector
There are three injectors (one for each cylinder), each of which are installed between the cylinder head and delivery pipe. It is an electromagnetic type injection nozzle which injects fuel into the intake port of the cylinder head according to the signal from the ECM.
When the solenoid coil of the injector is energized by the ECM, it becomes an electromagnet and attracts the plunger. Simultaneously, the needle valve which is incorporated with the plunger, opens, and the injector, which is under fuel pressure, injects the fuel. Since the lift stroke of the injector needle valve is constant, the amount of fuel injected at one time is determined by the length of time, during which the solenoid coil is energized.
Cold Start Injector
The cold start injector is an electromagnetic valve provided for the purpose of improving starting performance on a cold engine. It is controlled by the starter injector time switch so that it injects fuel only during a cold engine start. The shape of the nozzle tip allows the fuel to be injected in swirls, for better atomization of injected fuel.