All,

If you're following along here: https://www.brickboard.com/AWD/volvo/1657010/S70/cel_codes_p0172_pending_p0301.html

Then this is where I'm currently at.

Got my new fuel pressure tester gauge today and here is what I have found, and I'm stumped.

So for starters I attached the gauge and primed the rail by turning the key on and off till all I could get to was 38 PSI.

I believe that this is NOT an accurate leak down test, but I left if sit for 10 minutes, and within that time it dropped to 30 PSIs.

After that, I started the car and the gauge read between 42 to 44 PSIs while idling.

I revved it a few times and it read between 43 to 44.

I then proceeded to remove the vacuum line to the FPR and expected to see my gauge jump up. However what I saw was that it stayed the same value. So what does that mean to me? I also noticed that I had a pulsation coming from the vacuum line and not a steady pull. I believe I measured that it was pulling about 2 to 2.5 inches of mercury when I checked. Does that sound about right?

I then reattached the vacuum line and shut the car off, and here are my leak down test results.

@ shutdown, 38 PSI,
@ 10 minutes in, 40 PSI,
@ 20 minutes in, 38 PSI,
@ 30 minutes in, 30 PSI,
@ 40 minutes in, 28 PSI,
@ 60 minutes in, 22 PSI,

So as you can see, in my opinion, the car loses pressure rather quickly, but why???

Also I attempted to pull a vacuum at the FPR and from what I can tell it did hold a vacuum. I was running out of day light and my son needed the car, so I didn't spend much time with it, so I may have missed something there.

So in conclusion, removing the vacuum line from the FPR has no effect on the fuel pressure at the rail, there is a pulsation on the FPR vacuum line instead of a steady suck, but I don't know if this is normal or not, and finally the fuel pressure at the rail appears to bleed off rather quickly in my opinion, but I don't know what the spec is, and all I have to compare it to from a white block perspective is my 07 XC70, which holds much stronger and much longer.

Again as usual, any and all help on solving this lagging issue is greatly appreciated.

Matt
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1989 - 245, 1990 - 245, 1991 - 245, and 1993 - 245