Anyone have the fuel pressure leak down specs for a '99 S70 non-turbo B5254S ? TIA

Bill in Yardley, PA

 

From 850 NA Manual; yours should be similar if not the same:

6) Turn ignition off. Remove jumper wire between fuel pump
relay terminals No. 1 and 3. Reinstall fuel pump relay. Check fuel
system residual pressure. Pressure should not fall below 20 psi (200
kPa) in less than 20 minutes. If fuel pressure falls faster, check
injectors, pressure regulator, and fuel pump.

 

Thanks very much for getting back to me. My '99 S70 makes 40 PSIG "key on" and 42 PSIG running at idle. During the leak down test, it took 50 minutes to drop from 40 to 20PSIG. 3 hrs, 10.5 PSIG. Overnight, 0 PSIG. Normal?

Also I'm a little wary of assuming that specs for the 850 (FI system?) and the S70 (Motronic system w/ no return line or regulator on the rail) have the same spec.

In any event, the symptoms remain the same, occasional no start on (initial) cranking after sitting for a day or three. When it does start, it does so begrudgingly with much pedal pumping and running on <5cyl. Once started all is well. I'm starting to suspect an intermittent relay.

Thoughts?

TIA,
Bill in Yardley, PA

 

First your fuel pressure and drop rate seems normal to me.

Ah yes, good old (newer actually) returnless fuel injection systems...

FYI: here's a good article on the difference between these and older (like my cars) fuel injection systems (which have return lines):

http://www.aa1car.com/library/returnless_efi.htm

So have you done stage0 yet? New fuel filter could just fix it.

Beyond that, will take some troubleshooting; remember seeing another poster who found the fuel pressure sensor in the rail to be flaky, causing similar issues.

Have you got a scanner? If so, you should be able to monitor your fuel pressure in real time (or at least what the sensor is telling the PCM..). Comparing that to what a real (mechanical) fuel pressure gauge tells you could help identify a bad fuel pressure sensor...

 

hi gdog, I'd want to check my fuel pressure very soon too, where do you connect the fuel pressure gauge? also I noticed my generic scanner doesn't return the fuel pressure, do i need a volvo unit?

 

OK f88, I just looked through all 24 of your posts and (unless i missed it) could not find where you told us what MY your car is... know it's a S70 NA but not the year..

The '98 MY S70 was a dressed up 850; same mechanicals essentially. Which meant, well read my 2nd post in this thread:

================================================== ======
FYI: here's a good article on the difference between these and older (like my cars) fuel injection systems (which have return lines):

http://www.aa1car.com/library/returnless_efi.htm
================================================== =======

The '98 S70 NA has a mechanical pressure regulator in the fuel rail and a fuel return line going back to the tank.

In '99 they (apparently; I don't own one..) went to the returnless system described in the article; those systems will have an electronic fuel pressure sensor in the fuel rail and hence you should be able to read it via your scanner. So i will take a total WAG and say you have a '98 S70?

You should have a shrader valve on the driver's side (in USA) of the fuel rail. That's where you can hook up your fuel pressure gauge.

 

gdog,

The only "scanner" I have is an OBD II, which doesn't have much utility beyond reading key/on engine/off error codes. What type (and brand?) of scanner does what you're refering to (above)?

BTW, I repeated the leak down test (on a cold engine this time) and got different results the second time:

0 min 41 PSIG
10 min 40.5 PSIG
20 min 40 PSIG
30 min 40 PSIG
40 min 39 PSIG
50 min 37 PSIG
60 min 35.5 PSIG
80 min missed reading (Doh!)
100 min 28 PSIG
120 min 27 PSIG
180 min 23 PSIG

TIA,
Bill in Yardley, PA

 

The scanners I am talking about plug into your OBD II connector. Here's a pretty good link about scanners:
http://www.youfixcars.com/auto-scanner-reviews.html

From your numbers I don't see an issue with fuel pressure leak down. This indicates your injectors, fuel pump ck valve and regulator are holding pressure once they're under pressure, but that doesn't necessarily mean they are not intermittently leaking during pressure build-up (i.e. initial pump up as in starting the engine after 3 days of sitting). Obviously this is pure speculation; again fuel pressure gauge attached when the issue happens will give the most clues as to what's happening.

And you can't rule out an electrical issue too. But i do agree; your symptoms so far indicate a lean condition on cold start. Am assuming it runs perfect once warmed up?

 

Good point. When key is initally turned on after overnight sitting, pressure rises to ~20 PSIG at the rail. Cycle key on/off/on, pressure rises further. Not sure why the pressure wouldn't rise all the way to full pressure spec on first key-on? Does this indicate a problem, or normal?

Knowing how something is supposed to work certainly DOES make fixing it easier... I guess that's the only thing I'm missing (the "supposed to") :/

 

Interesting indeed... Again i don't have one of these newer vehicles with this non-return line system, but certainly doesn't seem normal to me.

What would be telling to me is, when you first keyed on, the gauge stopped at 20 psi, did you actually crank the engine and try to start it? Or did you cycle the ignition one or more times to get the pressure up to normal (over 40 psi) w/o ever cranking the engine?

If you can repeat this (pressure build-up stops at 20 psi) and it stays this low, even during cranking, then you definitely have an issue. And it will a bit more difficult to diagnose than the older return-line systems (since the return line is effectively in the tank..).

 

thanks gdog, mine's a 1997 NA with the blue nipple at the end of the fuel rail, so most likely the same setup as the 850 and a mechanical pressure regulator, so what kind of meter can I connect it to? Is it a generic kind of tool that I can purchase from ebay? thanks...

 

So I ran a flow rate test with my pressure gauge setup and came up with 74mL/30sec which is ~2.3 gal/hr or 8.9 L/hr. Seemed v. low, so I changed the fuel filter. Retest gave 4.2 gal/hr or 16 L/hr. Still quite low as compared to the only spec I could find, which was for a replacement fuel pump flowing 95L/hr! If that is correct, my flow rate is at 17% of specification.

I think a fuel pump replacement may be in order... thoughts, rebuttals or refutes? Specs from Volvo NA available from anyone? As always, TIA.

Bill in Yardley, PA

 

Sorry but i couldn't find any fuel flow specs. Wondering, if you're testing this at the schrader on the rail, then maybe it's being throttled by the internal pressure regulator? I.e. to really test the flow rate, would need to do it upstream of the regulator..

In any case, sounds like it improved dramatically with new fuel filter; as I suggested in post #4 of this thread, a stage0 may just fix it; have you done that recently?

Now as you suspect, it may be a tired fuel pump too. How many miles on the clock? These things tend to die right around 150K mls or so.

 

I plead ignorant what is a "stage 0"?

To answer your 2nd question, the car has 115k miles on the clock.

I think I may retry the flow rate at the pressure release schrader near the fuel filter.

I'm also wondering if the flow rate should be done by jumpinng the relay w/ the engine off, as opposed to doing the test w/ engine on? I've seen videos of this test being done both ways, so I'm a bit confounded.

As always, TIA...

Bill in Yardley, PA

 

• Stage0 is common terminology on many auto sites for full tune-up (plugs, filters, wires, etc. basically everything that wears out that has to do with the engine running well..)
• Yikes?!! Doing a fuel flow test at all scares the heck out of me; doing it with the engine running really scares me!! Fuel vapors are extremely dangerous; area must be very well ventilated.

F88: No offense but you should start your own thread about scanners if you're interested... or do a search; seen lots of threads about them here..

 

gdog: i'm sorry wasn't trying to hijack the thread just thought what i was asking was exactly similar to the thread so I'd thought I'll ask it here.. and i wasn't asking about OBDII scanners, i meant to ask what fuel pressure gauge I need, to do this fuel pressure leak down test... cheers