Q: 99 GMC Sonoma carbeurated or fuel injected

Hi There, The 1999 GMC Sonoma 4.3L V6 motor is a fuel injected motor that came with what is called a Central Sequential Fuel Injection (CSFI) system. In this application, there is one main fuel injector (called a MAXI injector) mounted in the center of the intake manifold on the 4.3L engine, and is hidden inside the split plenum manifold. Instead of spraying fuel directly into the manifold like a throttle body injector does, the MAXI injector routes fuel into six nylon fuel lines that have poppet-style spray nozzles on the end. When the pressure inside the lines reaches the opening pressure of the poppet valves (43 psi), fuel sprays out of the nozzles into the engine’s intake ports. If you need further help with your fuel injection system, please reach out to us here at YourMechanic as we are always here to help.