1997 850 NA manual transmission vibration at idle (also sorting out NA EVAP hose routing)

[abscate]

I don’t see the FPR vacuum going to the purge valve, actually I don’t see any FPR on the NA vacuum diagram

????

My measurements on my car (ME7) show the purge valve opens less than 10% of the time, I think fuel pressure regulation needs to be more like 100% enabled.

[v-janitor]

This diagram should get us on the same page in terms of what's connected to what.

As this depicts, the FPR vacuum line is serving double duty -- vacuum control *and* vapor to the evap canister.

In the Volvo vacuum diagram, the "FROM FUEL TANK" line is the line in question, and they don't depict the tee and connection to the vacuum control input of the FPR.

vacuum-lines-na-p80.jpg (67.22 KiB) Viewed 1087 times

Welcome to my confusion.

[abscate]

That diagram does not look right

I don’t have a pre 1999 car so I want those gurus to look at that diagram, I think it should look like this

I can say integrating the fuel pressure regulation into the purge circuit makes no sense operationally; fuel pressure regulation needs to be constant, while purge is low duty cycle

It’s either been incorrectly assembled or there are other accessories in play here

[v-janitor]

I agree with you that this is not how things should be, hence all my questioning, but this is how things are (and have been for the 23 years since I bought the vehicle). We're on the same "How can this be?" page.

Have a look at this post from tharde:

viewtopic.php?t=70284#p370028

... the key observation in which is:

"The fpr gets its vacuum from the purge valve line to the evap canister via a y-connector"

He's describing an S70, but the setup is the same as my '97 850.

There are exactly two lines that run from the tank to the engine bay -- fuel supply and this vapor/vacuum line. Even though this doesn't make sense (to me), I'm still pretty sure that I'm not imagining it.

[abscate]

I looked on my 1998 NA parts car sticker and sure enough, it also doesn’t give guidance on the FPR connection

Let’s wait for some help on this one from other stickers

[v-janitor]

Cool. FYI, my sticker is identical to the one posted by matthew1.

[abscate]

The Question of the thread:

Does anyone have a 1992-1998 NA vacuum hose sticker showing the Fuel Pressure regulator (FPR) or Pressure Regulator vacuum hose routing?

I know there are at least two types (FPR by tank, FPR by steering rack. FPR at rail?) but lets start with anyone of these right now

Here is what Im guessing is going on.

There have to be three fuel lines to your FPR - one feed from tank, one feed to fuel rail, and one return (the regulator part of FPR) to the tank.

There should be two vacuum (or non-fuel) lines - one from the manifold, and one to the snorkel (before the MAF so that is it metered).

On turbo cars the purge valve pulls vacuum from two places because a turbo can have intake manifold a vacuum or positive pressure.

I think someone got mixed up and set up the FPR the same way, on your NA car.

An NA purge valve is a simple puppy - it just needs intake manifold vacuum, and thats it.

And that is a guess.

[v-janitor]

Yes, there are 3 lines to my FPR, as expected and as described, and as depicted the the diagram I posted.

But my snorkel has exactly 4 openings: MAF, throttle body, PCV, and IAC, and my MAF is attached directly to the airbox -- no intermediary snorkel.

Here are some pictures showing all this.

Front view showing the connections to the throttle body and IAC:

Top view, showing the connections to the PCV, throttle body, and IAC:

Rear view, showing the connections to the MAF, the PCV (just to the left of the white vacuum line) and the throttle body:

Overall view, showing the connections to the throttle body, IAC, and MAF

Before someone else points this out - the snorkel is quite new (about a year old). It was replaced because the old one had developed a crack near the throttle body. But the important bit is that it was a direct like-for-like replacement, so even though it’s new, it’s identical to the original one.

[abscate]

If you look in Matt’s posting of the NA vacuum hoses

The purge valve has no Y connection, it goes straight to the fuel tank

It goes straight to the intake manifold tree.

[v-janitor]

Yes, I agree that Matt's sticker diagram is consistent with my car and (therefore) the diagram I drew of it — because the sticker diagram just says that the other end of the line goes to the fuel tank. Which it does. But while doing so it “tees off” to the vacuum input of the FPR under the rear passenger seat, near to, but physically in front of, the fuel filter.

The tee is located on said line, which starts at the fuel tank, “tees off” to the FPR physically just past the fuel filter, and then continues to the canister input. The canister output goes to the input of the purge valve, and the output of the purge valve goes to the nipple on the intake manifold.

I’ve seen some pics online of a tee near the purge valve. That’s not the case with my car.

I can take some pics if you’d like to see.