[Christ]

I wasn't talking about pump flow. You need a constant pressure, regardless of flow rates.

If you can't keep the correct voltage to the pump, you won't get the correct pressure, and you'll have less vaporization and your injectors will have to run longer to get the right amount of fuel into the engine.

To test this, Run your fuel pump at 6VDC, then 8VDC, then 10VDC, then 12VDC, then 14.4VDC, and record the pressure at the fuel rail for each voltage. As you increase voltage, rail pressure will increase as well.

The pump runs on variable timing, not variable electrical input. This means that it may click on and off 100 times a minute (on a non-return system) to supply the correct amount of fuel at the correct pressure. On a return system, it runs constantly at the specified voltage (100% duty cycle) and the regulator/return valve keeps the pressure and flow rates under control.

A simple mod when you're getting too much fuel is just to turn down the rail pressure. You normally do this by modding the pressure regulator, but on non-return vehicles, you hotwire the pump and control the voltage with an electrical circuit.