The Trainer #31: A Beginner's Guide On Using In-Cylinder Pressure Testing For Drivability Diagnosis

#engineperformance #incylindertesting #scope #pressuretransducer #picowp500

Have you ever stood peering into the engine compartment, scratching your head and wishing you could see inside the engine when faced with a drivability complaint? Wouldn't so many problems be easier to find if you could? Imagine being able to see exactly when the ignition event actually happened, or confirm that a valve that wasn't sealing as it should? How about verifying cam/crank synchronization without the need for a "known good" cam/crank sensor waveform or tearing the engine apart to access the physical timing marks?

You could do all this and more in minutes if you were using in-cylinder pressure testing as part of your diagnostic assault!

This test uses a pressure transducer and a digital storage oscilloscope (DSO) to monitor pressure changes in the cylinder while the engine is running. A transducer differs from a sensor in that the transducer is able to accurately measure the pressure while a sensor simply reacts to pressure change. The transducer converts the pressure measurements into a voltage signal that your scope can use to paint a picture of these changes on the scope's screen, bringing the idea of a traditional running compression test into the 21st century!

In the August 2013 edition of The Trainer, we'll show you how what accessories you'll need and how to set up a scope to perform this test. We'll also show you the basic elements of the in-cylinder running pressure waveform, and what they have to tell you. After viewing this video, we're sure you'll see how valuable a technique this is and how it can save you hours of time in the shop!

Bernie Thompson, if not the father of this technique is certainly one of the most well versed in its use, recently authored an excellent introduction to this testing method that was featured in our July 2013 issue. If you missed the print, you can always access the digital version at http://www.searchautoparts.com/motora...


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