Note. On vehicles equipped with a Delco Loc II audio system, before performing any work that requires the battery to be disconnected, check that the audio interlock is disabled.
The fuel system consists of a fuel tank, an electric fuel pump, a fuel pump relay, an air filter, and either a TBI central injection system (for engines with a working volume of 3.1 l), or from the system of distributed injection PFI (for engines with a working volume of 3.8 l). The main difference between the systems is the number and location of the fuel injectors.
Central injection (TBI)
The TBI system uses two injectors mounted in a common housing on the intake manifold. The injector is an electric solenoid to which fuel is supplied at a constant pressure. To keep the fuel pressure at a constant level, excess fuel is returned to the fuel tank.
Signal from the electronic control unit (ECM) opens the solenoid, allowing fuel to be injected through the injector into the throttle body. The amount of time the ECM holds the injector open determines the ratio between fuel and air in the mixture.
Distributed injection (PFI)
The PFI system uses six injectors located at the intake valve of each cylinder. Mixing ratio "fuel/air" controlled in the same way as in the TBI system. The throttle body in a multiport fuel injection system serves only to control the amount of air entering the system. Since each cylinder has a separate injector, much better ratio control is possible "fuel/air".
Fuel pump and fuel lines
Fuel circulates from the fuel tank to the fuel injection system and back to the fuel tank through twin metal tubes that run along the bottom of the vehicle. The electric fuel pump is attached to the fuel gauge inside the tank. The fuel vapor recirculation system directs all vapors and hot fuel back to the fuel tank through a separate recirculation pipe.
Exhaust system
The exhaust system includes an exhaust manifold that contains an oxygen sensor, a catalyst, an exhaust pipe and a muffler.
The catalyst is a device that serves to reduce the content of harmful substances in exhaust gases. A single layer catalyst is used in combination with a three pass (reduction) catalyst. Further, more detailed information regarding the catalyst is contained in chapter 6.