hoursaway1@comcast.net wrote:
> Question about fuel pressure indications, at fast idle 2200 RPM, fuel
> pressure is 42 PSI on EM2, if I switch on the back-up pump with the
> primary pump the pressure drops to 35 PSI, can here both pumps running,
> if I switch off either pump pressure goes back to 42 PSI.  My system is
> 13B, stock red injectors all four, pressure regulator is stock Mazda on
> the end of fuel rail with vacume connection from dynamic chamber.
> Thanks,  David R. Cook  RV6A Rotary.
>

Is your pressure sensor in backwards?

(I kid!  I kid!)