Contents: Central injection (TBI) ↧ Ported injection (PFI) ↧ Fuel pump and fuel lines ↧ Exhaust system ↧
Note: On vehicles equipped with the Delco Loc II audio system, ensure the audio lock is disabled before performing any work that requires disconnecting the battery.
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 PFI distributed injection system (for engines with a working volume of 3.8 l). The main difference between the systems is the number and location of 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 maintain fuel pressure at a constant level, excess fuel is returned to the fuel tank.
A signal from the Electronic Control Module (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 of fuel to air in the mixture.
Ported injection (PFI)
The PFI system uses six injectors mounted at the intake valve of each cylinder. The fuel/air ratio is controlled in the same way as in a TBI system. The throttle body in a port fuel injection system only serves to control the amount of air entering the system. Since each cylinder has a separate injector, much better control of the fuel/air ratio is possible.
Fuel pump and fuel lines
Fuel circulates from the fuel tank to the fuel injection system and back to the fuel tank through paired metal tubes that run along the underbody 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 tube.
Exhaust system
The exhaust system includes an exhaust manifold in which an oxygen sensor, a catalytic converter, an exhaust pipe and a muffler are installed.
A catalytic converter 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 catalyst (reducing) catalyst. Further, more detailed information regarding the catalyst is contained in chapter 6.
(The original article can be found on the resource «ChevyMan»)