Exhaust pulsation (ignition triggered) during cranking

The purpose of this test is to look at exhaust pulsations with the First Look sensor to assess engine condition whilst cranking.

How to perform the test

Connect the First Look Sensor to Channel A on the PicoScope using the 25 ft BNC to BNC cable as shown in Figure 1, then attach the sensor to the exhaust pipe as shown in Figure 2.

Now connect the Secondary Ignition pick-up Lead to Channel B of the scope and attach the clamp to the cylinder 1 plug lead. Once you have disabled the fuel system (may not be possible on a carburated engine), crank the engine until the display pattern stabilizes. You can adjust the timebase and voltage scales to achieve best signal display.

This test is useful when it is desirable to obtain cylinder specific data without the engine running. You will need to disable the fuel system to perform this test. This test allows us to look at the action of the valve train and cylinders, exhaust valve action per cylinder and problems with the head or head gaskets may be assesed.

Example waveform

Waveform notes

This waveform shows a consistent signal pattern on Channel A as triggered against Channel B on the same time line. Cursor lines are added to show trigger reference (sparkplug 1) and show the time between trigger events. We can use this information to determine the approximate cranking speed of this engine.

Waveform Library

Go to the drop-down menu bar at the lower left corner of the Waveform Library window and select, Exhaust / tailpipe pressure waveform.


This help topic is subject to changes without notification. The information within is carefully checked and considered to be correct. This information is an example of our investigations and findings and is not a definitive procedure. Pico Technology accepts no responsibility for inaccuracies. Each vehicle may be different and require unique test settings.

Suitable accessories

  • WPS500X Pressure Transducer


  • FirstLook Engine Diagnostic Sensor


  • Secondary ignition pickup (capacitive with BNC)


  • WPS500X Pressure Transducer Kit (with carry case)


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Guided test: Exhaust pulsation (ignition triggered) during cranking