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

{accordionfaq faqid=accordion15 faqclass="dotluvfaq help2 aligncenter headerbackground headerborder contentbackground contentborder round7" active=item0}


(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 2):


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


end faq

{accordionfaq faqid=accordion3 faqclass="darkhivefaq defaulticon headerbackground headerborder contentbackground contentborder round5" active=item0}

For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available as an eBook or paper book.

Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium. There is a 14 day free trial.

On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!