In this video I will show you how to test for spark on a GM type two waste spark system. How to test for proper fuel injector control and how to test fuel pressure and the fuel pump electrical system.

Finally I will show you how to get trouble codes from an OBDI GM with no scan tool

Engine Performance Diagnostics chapter 15 page 6 chapter 16 pages 9-13 chapter 18 pages 9-17


  • no start
  • start/stall
  • poor performance when it would start
  • low power
  • ran better with the MAF sensor unplugged

fix 50

  • replace faulty fuel pump

test shown

  • how to test for spark
  • how to test for shorted injectors using a scope
  • how get trouble codes manually by jumping the data link connector (flash codes)
  • how to test the fuel pump electrical system from under the hood

Tools used

  • Picoscope
  • inductive low amp probe

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

Related videos:

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


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


How to test fuel pressure, injector pulse and spark with basic tools:


Fuel Pump Electrical Circuits Description and Operation:


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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!