two pump styles are available, constant or intermittent run. A constant run type would be like the old mechanical injection where any un-used fuel is returned to the fuel cell. This is usually through a regulator with set pressure fuel going to injectors and rest returned so no spikes in pressure.
The on = off type pumps are more for street or carb systems and often have an internal regulator. If outlet pressure drops pumps turn on until set point is reached and then turn off again.
Watch for a high output pressure on a constant on type pump.