The CPI system began on the 4.3L engines in the early 90s and extended to the 5.0 and 5.7 engines around the same time with some slight variations. Around 1996 the CPI system became a SCPI which stands for Sequential Central Port Injection. The CPI had one central electrical injector, while the SCPI had an individual electrical injector for each cylinder. On both types there where mechanical "poppet nozzles" that sprayed the fuel into the intake runners. These systems had unique problems due to the injector assembly locations and the mechanical injector poppet nozzles. The vehicle being tested in this video is a 1995 Chevy S-10 Pick-up 4.3 L VIN W engine. The primary focus of this video is how to troubleshoot and repair a Central Port Injection system with an internal fuel leak.

Some other names for this system:

  • central port injection (CPI)
  • "spider injector assembly"
  • vortec injection system

Engine Performance Diagnostics chapter 16 page 8

symptoms 50

  • long crank time
  • severe rich running condition (P0172, P0175)
  • more gas mileage
  • check engine light
  • misfire trouble codes (P0300)
  • rough idle
  • stalling

fix 50

  • replace fuel pressure regulator

test shown enh 50

  • how to test fuel pressure
  • how to manually energize a fuel pump on a GM
  • how to determine if you have a fuel pressure bleed-down problem
  • how to determine the cause of the bleed-down problem
  • how to verify the the location of the leak that is causing the bleed down problem
  • how to replace just the fuel pressure regulator on the injection assembly
  • what to look for using an aftermarket part (you may break the housing!)

Tools used

  • fuel pressure gauge
  • jumper wire
  • needle nose vice grips
  • scan tool

end faq


(Chapters 14, 15,16) Fuel Delivery and Fuel Pressure Testing

Related videos:

How to identify a leaking fuel pressure regulator on a GM CPI system (part 1):

How to test an electric fuel pump (1997 4.3L Chevy Blazer CPI):

end faq