fuel pump voltage

[Paul Raley]

I have been measuring the voltage in my fuel pump(an 86 300zx turbo) and
found a few odd things.  The first finding was the obvious, a swinging
DC voltage between 9-12 volts with occasional 14volt readings (can't
figure why though, doesn't moven between 12-14 volts).  Then I switched
to AC readings, I noticed 16volts at a frequency between 60-70khz.  The
AC reading would sometimes fluctuate, but the more gas the car was given
the lower the AC voltage and higher the DC voltage.
Does the ECU convert the DC to AC to drive the pump and then convert it
back finally into DC again?  And what is the deal with the frequency?
Sometimes it jumps around, but I could not see any correlation to
throttle position and frequency.

Paul R