[dcb]

I'm having an epiphany in slow motion here.

I don't know if that pump will squirt out the exact same amount of fuel with each stroke/revolution, not like a gerotor pump would, but it might be close enough.

But if a pump (any pump) can turn on and off by itself within a pressure range as needed, then perhaps it is simpler and also "close enough" to just keep track of how long the pump has actually run. I.e. an 12 volt analog clock in parallel with the pump for proof of concept. It wouldn't be terribly instantaneous, but would be good for a trip. I think I'll have to try that, maybe a vacuum guage can close the gap on the lack of instant mpg.

therefore we have: miles traveled/(total seconds pump was on ON * average gallons per second the pump moves when installed)

Just have to log the start time, and the start miles and see how close it is at the next fillup to figure out gallons per second the pump is moving.