600hplt1sm

I don't know if this is a common reaction to a racetronix install but my fuel pressure at idle used to range around 38-42 @ idle and now its up around 44-48. I currently have the stock regulator on the car. Is this a correct reaction or does it point to the old pump being bad

Injuneer

Is the vacuum line still connected to the fuel pressure regulator? Is the line cracked?

600hplt1sm

Yes all vaccumn lines are on. Ill have to check to see if the line is cracked, But I noticed today that the pressure increase is pretty much at idle. Once I put the car in gear and am driving it the pressure is normal but it still flucuiates. Im just wondering if my gauge is faulty. Im getting ready to do the fuel rails in parallel with the -an fittings and i will have a gauge on the regulator and maybe i can check it then. I though FP was supposed to be pretty steady. Maybe iM wrong

Injuneer

The vacuum referenced fuel pressure regulator controls the DIFFERENTIAL pressure between the fuel rails and the intake manifold. That is the driving force for the injectors... the delta pressure between the rails and the manifold. That is the pressure that determines the flow rate through the injectors, not just the rail pressure. So the rail pressue has to vary based on changes in the inake manifold pressure (or vacuum). If you lose vacuum at idle, your fuel pressure will rise proportionally,