PWM fuel pump

[Dave Williams]

 All of the FI systems I've looked at so far use a fuel pressure
regulator referenced to manifold pressure.  The regulator normally
bypasses excess fuel back to the main tank or surge tank.

 Some newer cars use a resistor switched into the fuel pump power wire
to adjust fuel pressure for hot start.

 Some newer cars use deadhead or "returnless" fuel rails.


 On an add-on EFI conversion, running a fuel return line back to the
tank is a hassle, at least if you're paranoid like I am.  What problems
would be involved in controlling an in-tank pump by pulsewidth
modulation, to keep the fuel rail pressure constant and to not have to
run a return line?