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Fuel Pump Waveform Study
Posted to Technical Theory Forum on 5/21/2016 31 Replies

I recently scoped a fuel pump and noticed a couple of things about the waveform I was not sure about, so I am hoping to stimulate some thought and conversation here.

This fuel pump uses eight commutator segments, so every eight oscillations in the waveform should translate to one revolution of the armature. It is my understanding that, when viewing fuel pump waveforms at higher time scales and observing [an additional arch pattern for each revolution of the armature], this is an indication of worn armature shaft bushings, allowing the armature to wobble as it rotates.

Looking closer at this fuel pump waveform, I noticed one commutator segment consistently displayed [a unique blip in the pattern]. I am curios as to what might be the cause? What have you seen?

Also, again viewing the waveform over a longer time scale, I also noticed (what appeared to me to be) an interesting irregularity in each complete revolution of the armature. For the first half of the revolution, one can see each commutator segment using slightly more current than the last, which I assume is due to a decreasing gap brought on by the armature wobble. But then, for the second half of the revolution, the current suddenly drops for the next commutator segment, and then slowly rises again for three of the remaining four segments, similar to the original four, before dropping again for the final segment, [as highlighted here]. I am left pondering what is occurring to create this consistent pattern as well.

Please offer your thoughts on what may be contributing to these fuel pump patterns (maybe some of our illustrious iATN fuel pump guru's will chime in and offer their explanation as well).

Andy from Arizona

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