fuel pressure regulator?

Post by **confused_al** » 23 Oct 2011, 14:30

Well, that “thing” is NOT a FPR, rather the damper (Volvo calls “absorber”) is in fact the FPR for this setup (non-return fuel line). This setup is used for all P2 cars and they use the same “absorber” at fuel rail yet without that “thing”. Why?

Fuel pump for P2 cars has a built-in check valve preventing reverse flow therefore maintaining fuel pressure at fuel rail. Older generation pumps don’t have that built-in check valve, so what did they do? They added that “thing".

Thats why some sites just call the absorber the Fuel Pressure Regulator,
http://www.eeuroparts.com/Main/PartDeta ... id=1275658

waynej · Post by **waynej** » 23 Oct 2011, 15:19

Confused,
Please explain to us how the part you have pictured can possibly control fuel pressure. It has only one connection. It cannot be anything but a damper.

Maybe you can also explain how a check valve can control fuel pressure.

Post by **confused_al** » 23 Oct 2011, 16:29

Way,
Glad you ask that, with a return line the excessive pressure can be reduced by mechanically returning fuel back to the tank. This kind of mechanical regulator uses a diaphragm and spring combination within its housing with a vacuum source on the top side of the diaphragm to counteract the spring pressure when high demand dictates that higher fuel pressure is necessary.
Newer cars use more electronic approach, P2 cars, for instance have a electronic fuel pressure sensor attach to the fuel rail monitoring fuel pressure in a real time matter. ECU then controls the macro fuel supply pressure based upon that sensor and others’ inputs. However, some micro instantaneous pressure irregularities have to be curved and regulated, that is what this “absorber” is for.
BTW, that check valve is not for pressure regulating rather it is for flow regulating.

waynej · Post by **waynej** » 23 Oct 2011, 16:48

That all makes sense for the newer cars that have what you describe. My 96 850 has a real FPR by the fuel filter. Misha's first post on this thread showed a picture of a real FPR by the filter. Others have sent diagrams of FPR's by filters. Giving info on a newer model is confusing to Misha and others who may read it.
I am curious about the newer system. What year did Volvo start using it? It sounds like it has a fuel pressure sensor, is it on the rail. Does the ECU control pressure by modulating voltage to the pump or by pulsing the power to the pump and changing the duty cycle? It sounds like the newer system should give us longer pump life.

PS. The higher fuel pressure is not for higher demand. It is to keep a constant pressure differential between fuel in the injector and varying manifold vacuum. Demand is satisfied by the ECU sending a longer pulse width to the injectors.

Post by **misha** » 23 Oct 2011, 17:02

I'm really in the dead-end right now.

Some of you guys claims that the "thing" i have is fpr and some of you claims that it is not.

Confused_al claims that the "thing" i have is "cpl"(capillary pump loop).

Maybe all of you are right.

But,u.s versions of these cars are very different than european versions,or vice versa.I suppose that this fact is the MAJOR problem.

Later european models(last models) of 850's made in '97 are actually early versions of s,v70 for u.s market.I think that i got that confirmation from Lee,but i'm not sure.

This far i can tell this... IF the little "thing" i have near fuel filter is NOT fpr then i really DON'T have it at all.That can explain Confused_al's post that non-return fuel system have ONLY fpd/apsorber which is attached at fuel rail.

IF the fact that later european models of 850's are actually earlier u.s. models of s,v70 is true,then maybe i have fpr at the end of the steering rack like j'blackburns car have(he have s70 as i recall) and i need to check that as soon as i can.

If j'blackburn would like to post a picture of his fpr and it's location,that would clear this topic once for all times.

Thoughts?

waynej · Post by **waynej** » 23 Oct 2011, 17:27

Misha, Regardless of differences in years, models, countries, etc. you posted a picture of your FPR near the fuel filter. It was identical to the FPR in my 96 850. I think you also said you have an extra FPR. If it is a real FPR with 3 connections, hold it next to the thing by your filter, it should be the same.
I recently ordered a new FPR from eEuro parts. They show it fits 96-98 850 and S70 etc. part # 9146761. The part they sent was the correct one. It installs on rail on some, near filter on some and behind right side of steering rack on some.
Here's the link to eEuro page: http://www.eeuroparts.com/Main/PartDeta ... id=9146761

Again don't waste your time changing it till you make sure you have vacuum to the small nipple on the FPR.

Post by **confused_al** » 23 Oct 2011, 17:35

misha wrote:Confused_al claims that the "thing" i have is "cpl"(capillary pump loop).

I would like to point this out, Its NOT my claim, it is from VIDA/VIDAS (both called the same thing).

Post by **misha** » 23 Oct 2011, 17:40

waynej wrote:...I think you also said you have an extra FPR. If it is a real FPR with 3 connections, hold it next to the thing by your filter, it should be the same.

Yes,i have older style fuel rail with vacuum controlled fpr still attached to it.

I'll check the fitings as soon as i have time and i'll report back.

Post by **misha** » 23 Oct 2011, 17:46

confused_al wrote:I would point this out, Its NOT my claim, it is from VIDA/VIDAS (both called the same thing).

Ok,that's what i meant,but i didn't expressed myself corectly.

waynej · Post by **waynej** » 23 Oct 2011, 17:47

The FPR is in a closed loop with the pump and it's fine if Volvo calls this loop a "cpl". The term non-return is a misnomer, the single pipe system still has a loop, it's just a much shorter loop. Non of this makes the FPR not a FPR. Volvo does not use the "new math" and this is not rocket science.

fuel pressure regulator?

Re: fuel pressure regulator?