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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