On both the 2.4L and the 3.1L engines, a Sequential port Fuel Injection (SFI) system is used for more precise fuel control. With SFI, metered fuel is timed and injected sequentially through injectors into individual cylinder ports. Each cylinder receives one injection per working cycle (every two revolutions), just prior to the opening of the intake valve. The SFI system PCM has four injector drive circuits, one for each cylinder.
Both engines use Bosch® injectors, one at each intake port. The injectors are mounted on a fuel rail and are activated by a signal from the PCM. The injector is a solenoid-operated valve which remains open depending on the width of the electronic pulses (length of the signal) from the PCM; the longer the open time, the more fuel is injected. In this manner, the air/fuel mixture can be precisely controlled for maximum performance with minimum emissions.
Fuel is pumped from the tank by a high pressure fuel pump, located inside the fuel tank. It is a positive displacement roller vane pump. The impeller serves as a vapor separator and pre-charges the high pressure assembly. A pressure regulator maintains 28-36 psi in the fuel line to the injectors and the excess fuel is fed back to the tank.