should the FPR flow something when it has no boost or vacuum on it?



Loi



this is for an s4 TII by the way.

I think it should. I have never tested it though. I remember pulling the vac line off on an n/a one time. And if the fpr wasn't bleeding off fuel as it should, the car I would imagine would have either started to run dog rich or the injectors would have started leaking since fuel pressue would start to sky rocket.

i've got 2 stock FPR's and neither of them flow aything when no vac line is attached. just wondering if both are bad or what?



Loi

I've never heard of the stock fpr going out. Seems strange that you have 2 that do that. Maybe they are fuctioning correctly. Why are you testing them anyhow?

with no vacuum line attached they should still flow fuel.



no vac line == atmosperic pressure, so having no vacuum line connected is comparable to the condition your FPR experiences around WOT (it will still have around 1-2inHg due to the throttle plates and air filter etc though)



on my setup WOT is like 0 inHg to the MAP sensor.



the fpr is supposed to compensate for vacuum on the other side of the injectors (and boost on a t2), so when the fpr gets 0 vacuum, it is supposed to regulate the static fuel pressure.



when it gets N vacuum, it regulates static fuel pressure - N.... when it sees boost, it regulates static fuel pressure + N psi boost.... so yes, it definitely should flow fuel @ atmospheric.

i just checked mine, i cant blow thru it

probably can't blow hard enough.





the fpr will see atmo pressure for a short time when transitioning from vacuum to boost on a turbo car, it definitely has to flow fuel under this condition.

yeah i can only blow 1-2psi the fuel pump can do like 40!

what the hell are the chances that i would get 2 non-functioning fpr's!!!!



i really must have the worst luck ever!!!!



Loi



o, and i'm testing them cause my car won't start and i'm pretty sure its a fuel thing cuz it starts when i spray starting fluid into it.



yeah, and my car won't turn over when its on the ground but will when its on jackstands. thats a whole different problem though....damn project cars, damn them to hell!!!!!!





i didn't mean that....

Sure...

Mazda spec is 35psi at vacuum or under -"0"

At "0" it supposed to step up to 40psi.

If this is a turbo FPR, then it's a 1:1 ratio for boost versus pressure.

i.e. - at 10psi of boost, the fuel rail pressure should be 40psi + 10psi = 50psi.





-Ted