On vehicles with a 3.1L (V6) engine, the Tire Boost Injection (TBI) replaces the conventional carburetor above the intake manifold. Cars with a 3.8 L engine are equipped with a distributed injection (PFI) system. TBI systems are controlled by the ECM electronic control unit, while PFI systems are controlled by the PCM control unit. ECM/PCM systems monitor engine operation and regulate the corresponding fuel / air mixture supply (for a complete description of ECM/PCM control systems, see chapter 6).
An electric fuel pump, located in the fuel tank with a fuel sensor, forces fuel into the system through the fuel supply line and fuel filter.
Note: The 3.1L engine has a dual turbine pump (provides medium pressure), while the 3.8L engine is equipped with a vane pump (provides high pressure). In addition, the 3.8L engine is equipped with a pulsator (see illustration 7.8) to equalize pressure fluctuations during pump operation.
The pressure regulator maintains a constant fuel pressure. Part of the fuel is returned through a separate line to the fuel tank.
The TBI basic unit consists of two main castings: the throttle body with the Idle Air Control (IAC) valve that controls air flow, and the Throttle Position Sensor (TPS) that monitors the throttle angle. The injector body consists of a fuel supply meter with a built-in pressure regulator and a fuel injector for supplying fuel to the engine.
The injector is a solenoid-based device controlled by the ECM. The ECM energizes the solenoid, which lifts the valve off its seat. Fuel is injected under pressure above the throttle valve. Fuel not used by the injector passes through the pressure regulator before returning to the fuel tank.
On port fuel injection (PFI) systems, the throttle body has a valve that controls the amount of air entering the engine. The throttle body houses the throttle position sensor (TPS) and IAC valves.
The distribution pipe is located on top of the engine. It distributes fuel to individual injectors.
Fuel is supplied to the tube through the fuel supply line and through the distribution tube gets to the pressure regulator. The regulator maintains constant pressure at the injectors.
The remaining fuel is returned to the gas tank.
[The text of the article was obtained from the website «ChevyMan»]