'98 S70 GLT 2.4L VVT - Low fuel psi @ rail

[1998 s70]

Ok so A little history,

While waiting for a new (2nd warrantied) radiator to arrive I was driving about a month and a half ago and it just died in traffic. Had to tow it home and just stored it until I could get the radiator in (since I was fearful that it was a blown Head gasket)

So last week I finally got the radiator in (took my time and did it right) then got it diagnosed since it would only crank over and start but couldn't hold an idle. Mechanic checked the cyl. psi and the fuel psi @ the rail.

Cylinders were good @ 125-130 psi (No head gasket issue)
35 psi @ the @ the fuel rail Not good need 50-60 psi
So he thought it should either be the pump or the relay. He didn't have one to switch out so I searched the forum and found the jumper technique (paperclip from terminal 15-87) which allowed it to start more consistently, and finally idle at around 500RPM. Ran it for 30 -40 min. or so while I bled the radiator and replaced the water with coolant. Whew no leaks. Stoked!!!

Anyway so after about the first 15-20 min. shortly after the fan kicked on, the idle came up to about 750 which is good yet it was definitely running rough. So it starts much better now but still running rough. tried to take the jumper/paperclip out of the relay and put the relay back in and start it, yet with no success. I then put the jumper back in and she started right away and idles @ 750 no prob. yet still runs rough. Too rough to even drive. Ok so I know I need a new relay (RIGHT!!!)

Well I'm not 100% convinced so I am continuing to diagnose because I just don't know if that relay will restore the psi back to full when I receive it in the mail. I don't know if I should fully expect it to fix the issue. Is she running rough because the relay isn't installed, which should fully send the proper amount of electricity to the pump. Oh and BTW the pump is running and I can hear it whirr (continually I might add) while I am in the car with the door closed.

I read as much as I can find and found the fuel pressure regulator location as well as the rail has a pressure regulator also but not sure about the fuel line check valve (yet I've rule that out since it starts just fine now). I should get a fuel pressure gauge tester soon if not today.

If the relay doesn't fix it I am assuming the FPR is bad but I don't kow how to isolate that and diagnose it for my car. Your help is greatly appreciated in advance.

Thanks in advance, for reading my long post.

[jblackburn]

On a 98 turbo, 38-40 psi is normal fuel pressure for idle speeds. A bit beyond that at higher engine loads.

50-60 is for a return less fuel line system on the non-turbo 98 and later models.

Check valve is working fine if the car starts without hesitation on the first crank.

Fuel pressure regulator is behind the right front tire, near the steering rack.

[1998 s70]

jblackburn:
Thank you I had no idea the pressure should be so low.

Car starts fine on the first crank when jumpered without the relay but then doesn't start at all with the relay so I am assuming the relay is still the expected problem?

Yes I found the FPR but not sure if this is the issue, neither do I know how to diagnose an FPR. Any ideas what my issue seems to be othe than the relay?

[1998 s70]

Update: I installed a new fuel pump relay and it works better than the old one... however... it stills runs super rough just like it did when it was jumpered.

I know it for sure needs a new pcv system since now when running it is smoking like crazy out ta the dipstick, but could that be the problem? I'm doubting that is my total problem.

One thing's really got me thinking is that when I replaced the hose coming from the idle air control valve to the intake manifold, the new hose inlet size was between a half and two-thirds smaller than the older one. I'm concerned this is something I should check to fix since it is so much smaller.

I'm stumped other than it could be the fpr. It's not the pump, relay, nor the spark, and from what jblackburn is saying the fuel pressure is good, neither have I found any stray vacuum lines, IDK. Help is greatly appreciated because my second job depends on it. Thanks

[1998 s70]

Sorry but could use a bump. Really need some help.

[jblackburn]

Sorry I haven't replied.

The fuel pressure regulator is behind the front passenger wheel, near the steering rack on the frame of the car. Locate it and disconnect the vacuum line going to the regulator, and smell it for fuel/see if it's wet. This can cause the car to run rich.

Aside from that, double-check your air hoses to/from the turbo for any air leaks whatsoever. This sounds more like an air metering problem than a fuel delivery problem to me.

[1998 s70]

Yeah I did see another post on that fpr check somewhere and I need to do that. I dabbled last week with the vacuum hose but couldn't get any leverage to get it off to check but I need to get back under there and get it off to smell it. Any ideas on the IAC valve exit into the intake, and the pcv concern. I agree that it really feels like an air problem and I've checked the vacuum lines and turbo lines multiple times.

[jblackburn]

Any ideas on the IAC valve exit into the intake?

What kind of hose did you replace it with?

Have you reset the computer via a battery disconnect once changing the hose? It should be able to adjust the idle to it, but that hose would not make the car run bad at anything over idle.

As for the PCV, run with the dipstick slightly askew for now. Change the PCV system out as soon as you can. The small vacuum hose is probably broken somewhere along the routing from the turbo hose to the other side of the intake manifold.

[echase76]

I second the air metering issue. Check for vacuum leaks and check your MAF. If you unplug the MAF then start the car how does it run? You can clean your MAF, but if it really bad it has to be replaced

[cn90]

Post a few photos of your current setup to see if we can spot the problems for you.