In this video I will be showing you how to use starter current to determine cylinder compression. First I will show you a known good pattern, then I will simulate a no compression problem in one cylinder by removing a spark plug. Finally, I will show you how to synchronize the starter current waveform with an ignition firing event in order to determine which cylinder in the firing order has the compression problem.

Engine Performance Diagnostics chapter 1 pages 17-23

symptoms 50

  • check engine light (code 26)
  • no driveability complaints

fix 50

  • replaced engine computer and all 6 fuel injectors

test shown enh 50

  • cranking compression test with a scope and high amp probe
  • how to synchronize a compression waveform to ID the no compression cylinder
  • how to perform a clear flood crank
  • how to use a single trigger setting on a scope
  • how to set a filter on a scope waveform

Tools used

  • Picoscope Automotive 4 Channel Scope

end faq

Playlist

(Chapter 1) Misfire ID, Compression Tests, Vacuum Leaks, Fuel Trim, Head Gasket, Restricted Exhaust, Low Power, DMM

Related videos:

How to perform a compression test with a scope (Verus-Vantage) :

How to check for a jumped timing chain or belt:

2002 Ford Escape 3.0 Misfire-wrong connector on 2 coils:

Relative Compression Test variables (3 cylinders with no compression):

Honda Civic 1.7 (start, run, stall case study):

end faq


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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