Long ago I had a fading fuel pump in the '93 Suburban, starting on the home
leg of a road trip. Got home OK, but it was the dead of winter, too cold and
snowy to comfortably change it outside. Needing to go to the dealer for a
recall inspection anyway, I asked them to just change the pump based on its
symptoms.
A genius at the dealer promounced the pump perfect (pressure test), but tried
to sell me lots of other parts, even including the fan clutch (which over
120,000 miles later is just fine). Took the truck home and kept looking for
the problem, "knowing" it wasn't the pump.
I finally found someone who could do the diagnosis - he put his scope meter in
series with the power line to the pump motor, and had a perfect picture of the
condition of each segment of the commutator. The commutator was worn
completely through in several segments when I cut it apart for a post-mortem.
New pump and all was well.
Now, I might have another dying pump in the truck, but it's only seemed so
once and now it's fine. Before I just change it because it's got 130,000
miles on it, is there any simple way to accomplish this scope diagnosis
without owning an actual scope ? Maybe with a simple circuit and a laptop ??
Karl
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