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.

 

WARNING

Uninsulated HT pickups are designed to clip around double-insulated HT leads only – they are not designed for direct connection to a hazardous live voltage.

To prevent injury or death, when connecting or disconnecting an HT pickup:

  1. switch off the ignition
  2. clean the HT leads
  3. inspect them for damage
  4. clip the HT pickup over the desired undamaged HT lead
  5. ensure all test leads are kept clear of hot or rotating parts before starting the engine

 

How to perform the test

View connection guidance notes.

Note

You must disable the fuel system before carrying out this test.

  1. Insert the First Look Sensor into the vehicle exhaust tailpipe and connect to PicoScope channel A.
  2. With the ignition off, connect a secondary ignition pick up around the HT lead for cylinder number 1 and to PicoScope channel B. Ensure the secondary pick up has a good earth.
  3. Minimize the help page. You will see that PicoScope has displayed an example waveform and is preset to capture your waveform..
  4. Start the scope to see live data.
  5. Crank the engine until the waveform stabilises (3 to 5 seconds).
  6. With your live waveforms on screen stop the scope.
  7. Use the Waveform Buffer, Zoom and Measurements tools to examine your waveform.

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.

GT129-2

Disclaimer
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

  • FirstLook Engine Diagnostic Sensor

    £449.00

  • Secondary ignition pickup (capacitive with BNC)

    £58.00

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Guided test: Exhaust pulsation (ignition triggered) during cranking