Voltage controller?

[Clarence L.Snyder]

Use a voltage to grequency conversion, then have the frequency output
drive a 555 oneshot. By tuning both the frequency output and the pulse
width you pwm control the pump.
I'm no engineer either, but both circuits are bretty simple. Could
likely use 555 for both stages, or even run one as a monostable with the
MAP connected to the control terminal - would give you roughly 2:1 ratio
range?