This problem is specific to GM vehicles built from the late 80s through the early 90s. Here is a partial list of the cars that used this style fuel injector.

    • 5.0 and 5.7 in the Corvette and Camaro
    • 2.8, 3.1, 3300 (Chevy, Buick, Olds, Pontiac)
    • 1.9 (Saturn)
    • 4.9 (Cadillac)

The first time I ran into one of these, I mistakenly replaced the engine computer in an attempt to fix the no injector pulse condition. It is strange that one shorted fuel injector can cause all the other injectors to not fire, but this is exactly what can happen with a group fired system. “Group fire” means there is only one transistor in the computer that controls all of the injectors at the same time.


Engine Performance Diagnostics chapter 18 page 12-18

symptoms 50

  • intermittent misfire
  • no start
  • no injector pulse
  • rough idle
  • misfire
  • starts and stalls
  • failed emissions

fix 50

  • replace ALL fuel injectors

test shown enh 50

  • how to measure injector current from a common location
  • injector current ramp
  • injector pulse test with a noid light
  • how to verify injector power supply

Tools used

  • scan tool
  • lab scope
  • digital multimeter
  • injector noid light
  • test light

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(Chapters 17, 18 and 19) Fuel Injector Testing

Related videos:

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


GM 3300 Intermittent no start rough idle (shorted injectors):


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


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.

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