The purpose of this test is to evaluate the correct operation of an inductive distributor pickup based on the output voltage and frequency during cranking and engine run conditions.
Connection for diagnostic work will vary dependent on application.
Technicians should whenever possible gain access to the test circuit without damage to seals and insulation. If this is not possible then make sure appropriate repairs are completed.
General connection advice
PicoScope offers a range of options within the test kits.
Dependent on difficulty of access, choose from:
Testing sensors and actuators (to include relevant circuit/connectors):
The connection will vary depending on the distributor set up. This may either have the amplifier mounted directly onto the body of the distributor or be remotely mounted in various locations.
If the engine is a non starter then select Go and crank the engine for around three seconds to capture your cranking waveform.
As the metal rotor spins, a magnetic field is altered which induces an AC voltage from the pick-up. The output voltage rises as the metal rotor approaches the winding, sharply dropping through 0 V as the two components are aligned and producing a voltage in the opposite phase as the rotor passes.
The voltage produced will rise from as low as 2 to 4 V when cranking to over 50 V at high engine speeds.
This particular type of pick-up generates its own signal and therefore does not require a voltage supply to power it. Recognisable by its two electrical connections, the pick-up is used as a signal to trigger the ignition amplifier.
The voltage produced by the pick-up will be determined by several factors, these being:
There are two types of permanent magnet pick-ups these are called Annular and Limb. The distinguishing factor between the two types is that the limb pickup has only one reluctor point where as the annular will have a reluctor point per cylinder.
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.
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October 21 2016
Good catch on the text, we’ve made that adjustment. Sadly we do not have the specific details of the vehicle used within this Guided Test.
March 28 2016
just a correction..the pickup is not “invariably mounted on the distributor shaft”..the spinning metal points are mounted there, called a reluctor.
The pickup is mounted stationary within the distributor.
Thank you for the voltage readings ; what pickup this is, would help the information..