Fuel Metering System

Fuel Injection Control.:

FUEL METERING SYSTEM
The fuel metering system is made up of the following parts:
^ Fuel supply components (fuel tank, pump and lines)
^ Fuel pump electrical circuit
^ Fuel rail assembly, including:
a. Fuel injectors
b. Pressure regulator
^ Throttle body assembly, including:
a. Idle air control (IAC) valve
b. Throttle position (TP) sensor

BASIC SYSTEM OPERATION
The fuel is delivered to the fuel rail and circulated through the system by an in-tank fuel pump. The fuel gage sending unit is mounted on the side of the pump module. Fuel is pumped through a fuel supply line to an in-line fuel filter. A pressure regulator on the fuel rail keeps the fuel pressure at the fuel injector between 214-306 kPa (31-44 psi) depending on intake manifold vacuum. Excess fuel not needed by the fuel injectors is returned to the fuel tank by a separate line. The fuel pump is controlled by the PCM through the fuel pump relay.

FUEL SUPPLY COMPONENTS
The fuel supply is stored in the fuel tank. An electric high pressure fuel pump, located in the fuel tank with the gage sending unit, pumps fuel through an in-line fuel filter to the fuel rail assembly. The pressure regulator, part of the fuel rail assembly, keeps fuel available to the injectors at a controlled pressure. Unused fuel is returned to the fuel tank by a separate line. Nylon fuel supply and return lines are routed along the left-hand side of the vehicle from the fuel tank. In-line connections have been installed at the tank, fuel filter, and engine for ease of assembly and serviceability.

FUEL PUMP ELECTRICAL CIRCUIT
When the ignition is first turned to the On position, without the engine running, the PCM turns the fuel pump relay On for two seconds. This builds up the fuel pressure quickly. If the engine is not started within two seconds, the PCM shuts the fuel pump Off and waits until ignition reference pulses are present. As soon as the engine is cranked, the PCM turns the relay On which powers the fuel pump.