Start-up Ecotality taps NASA technology for a system that can feed a vehicle's fuel cell on-demand. Images: Hydratus at work In a software-driven world, it's easy to forget about the nuts and bolts.

There could be a couple of things going on here. The first is that these engines were old-fashioned mechanical fuel-pump units, so they need to be primed. That involves getting all of the air out of ...