Fuel pressure regulator question....99 volvo v70xc

V70xc1999 · Post by **V70xc1999** » 13 Apr 2019, 14:26

Ok so I was hearing a hiss comming from around my fuel presure regulator....kinda tracked it down but could not pinpoint. So I replaced all gas lines conecting and around the FPR. Now with all lines I still heard the hiss and upon inspection the hiss is coming from the bottom of the plastic houseing that you mount the FPR to. (My car is running lean).....is this a breather vent or something or should this not be happening? My guess is no it shouldn't!!!! Thanks

Post by **abscate** » 13 Apr 2019, 14:50

Take a picture and put an arrow where the noise is coming from, 99 don’t regulate fuel pressure by vacuum so there are no FPR vacuum hoses to leak!

V70xc1999 · Post by **V70xc1999** » 13 Apr 2019, 19:42

There is one vacume hose comeing from it and 3 fuel lines.....its on top of fuel tank....iys leaking from where the FPR mounts with 2 bolts onto plastic piece that 2 of the fuel lines conect to.....how do I post a pic on here

V70xc1999 · Post by **V70xc1999** » 13 Apr 2019, 20:30

: Pic

pic

V70xc1999 · Post by **V70xc1999** » 13 Apr 2019, 20:31

pic

V70xc1999 · Post by **V70xc1999** » 13 Apr 2019, 20:33

Its not that vacume line thats leaking I have scence switched it.....it is cimming from plastic mounting bracket

V70xc1999 · Post by **V70xc1999** » 13 Apr 2019, 20:40

I was also told that this car didnt have idle control valve but isnt that what this is?

V70xc1999 · Post by **V70xc1999** » 13 Apr 2019, 21:06

pic of it out of car

Post by **jimmy57** » 13 Apr 2019, 23:08

The fuel pressure regulator has a diaphragm and on earlier models manifold vaccum(or pressure) was used to keep the pressure constant inlet to tip of injector. On the last ones to use FPR mounted in the junction in rear near tank the diaphragm is there but if it were to leak it needs to go somewhere other than under the car so the hose goes to tank. The diaphragm can't be sealed or it would not regulate properly. The FPR hisses as the pumped fuel builds pressure and pushes on the diaphragm and once the pressure gets to the target value as determined by the spring bearing on the "dry" side of diaphragm it pushes the diaphragm center metal seal disc off the relief port tube and the fuel hisses passing out to relief port.

V70xc1999 · Post by **V70xc1999** » 13 Apr 2019, 23:20

It should be leaking air out or sucking air in where if I put my finger over it....it will change the sound of air flow?....the regulator is makeing it's reg. Circulating noise....then there is a air leak that changes if I cover a cpl of different spots...also is that a idle air control in the back by the charcoal canister?