Part 1

This vehicle came in with good spark and no injector pulse. In part 1 of this case study I discuss with my class what this particular computer system needs to provide injector pulse.

Engine Performance Diagnostics chapter 18

symptoms 50

  • intermittent no start with good spark and no injector pulse
  • hesitation
  • misfire

fix 50

  • replace shorted fuel injectors

test shown enh 50

  • how to test for a reference pulse
  • how to verify the ECM is receiving an RPM signal
  • how to speed up scan data parameters
  • how to test for injector pulse
  • how to enter a clear flood mode
  • injector voltage waveforms
  • injector current waveforms

Tools used

  • scan tool
  • lab scope
  • low amp probe
  • back-probing tools
  • test leads

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(Chapters 17, 18 and 19) Fuel Injector Testing

Related videos:

GM Bypass Ignition System Operation (part 1):


How to test for shorted fuel injectors (1987-1994 GM Cars):


No Start No injector pulse (shorted injector) part 1:


No Start No injector pulse (shorted injector) part 2:


Rough idle, false MAP codes intermittent no start (shorted injectors) GM :


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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!