A "thought" is all I have for you. I had similar symptoms on a car years ago .... stalling, less power as the gas level in the tank dropped. Over time the problem worsened ... but it seemed to get a period of refreshment with each fill-up. I finally came up with the following theory and acted upon it.

It can be understood that as the tank level drops, there is less "head" to force fuel into the tank mounted tank. Therefore the pump would have less output pressure as the tank fluid level drops. What else? What if there is some loose contamination of some sort swirling around in the tank ... that gathers on the pump inlet screen ... being washed away with each flood of gasoline when the tank is filled ... to be deposited back on the inlet screen as time passes and the level drops. ??

In my case, a new pump inlet screen and a tank cleaning solved all.

 

Sounds like a loose connection on the pickup tube, sucks air. I have even seen it on transmissions.

Good thing it has an easy workaround, just keep it above that level. Kinda a pain to fix though.

A bad pump that couldn't pump when the tank was a little low would cause other low fuel pressure issues so I doubt that is the problem.

 

Not from Volvo experience

But from many years with BOSCH parts experience, I think there is a fuel sender or some sort of in-tank pump and I think yours is dying. I would check there first (not a DIY at least for me).

 

Thanks for the tips! I'll start looking them down.

There's more to add to this, After the stall. It started up just fine (no power loss) and ran for another 10-20 miles till we got gas. Also a CEL came on, haven't had a chance to pull the code yet but I'd bet it's another emissions issue.

If it were a bad sender or junk in the filter wouldn't the symptoms persist? I may try checking the code to see what it is, if it's another emissions issue would a stuck valve in the emissions system cause this? It seems that it happens only at lower tank volumes which would mean increased vapor and emissions to manage no?

 

Now that you have the code available, you need to start with that.

 

Reminds me of my buddy when his ex put sand in his jeeps gas tank. Always died at 1/4 tank. There's a screen that keeps debris from getting out of the gas tank. But as the tank emptied it sucked harder and pulled the sand towards the screen and also created a little mound that blocked the fuel.


Sent from the seat of my pants

 

TheCastro, that is much like what I was trying to describe in my posting. .....And as gasoline is added to the tank, the blockage will be washed away temporarily by the flowing fresh gasoline.

 

Had to remove the gas tank to fix it though.


Sent from the seat of my pants

 

I was lucky to have a floor access hole to the tank and pump. But I've had to drop several fuel tanks in the past on other units.

BTW, I have removed from gas tanks some strange things. Once some plastic screens like those that are in the nozzles of plastic emergency fuel "cans" ... and once, some small plastic bags, much like candy wrappers, swimming around in the fuel.

 

Sounds like one of the fuel level sensor floats is hanging up, giving you a false reading, & you're running out of fuel.

 

All good ideas, only problem is that you probably have to drop the tank to see. Dirt in the tank would probably show up in the fuel filter also.

The theory of the stuck float would be easy to check:
- watch the gauge, does it go down and then stop at 1/4 and hold there?
- if it runs out, do you have to add a complete tank capacity to fill it? If it was actually at 1/4 tank you would add less then the tank capacity.

 

http://www.snopes.com/autos/grace/sugar.asp

 

Alright More Info

Sorry I've been out of contact recently, busy week. So more info today when we pulled the codes:

Two weeks ago when we pulled the CEL codes they were related to gross evaporative emissions leaks so we pinpointed the gas cap as the likely culprit. We replaced the gas cap and things went well till the stall last week, but that was the only stall!

Interestingly, after the stall it started up again and ran fine, once we put more gas in it never hesitated or did anything else that would make you think anything was wrong. The CEL even went away. Well I let it go back to 1/4 tank to see what it'd do and again it threw a code but no stalling, no hesitation etc.

I pulled the codes and this time they're not emissions but rather with the fuel pressure (P0089 and P0193). Looking these up it appears that our culprit might be the fuel filter.

This would make sense as if clogged it would cause higher pressure on the tank side of things when on low tank (more air space) and probably led to the cap blowing out and the evap leak recording. With the new cap on the leak isn't there so the sensor is throwing a fit and probably causing the engine to stall out.

What do you all think? I'm going to go pick up a fuel filter tomorrow and install to see if that alleviates the issues. If not then next will be the sensor. Hopefully the pump didn't get any damage from the added stress.

 

Does your model also have an in-line (out-of-tank) fuel filter?

 

When was the last time the filter was changed?

 

From what I've read I have an inline (out of tank) filter. It's an '05 V8. As for when it was last changed, I have no clue. Bought it 3 months ago w/ 74k miles on it. My guess is they never changed it.

After clearing the code today it came back again tonight when driving. I'll go check tomorrow to see if it's the same (p0089 or p0193) or if it's the emissions leak coming back.

Hopefully I'll get to the root of this, it's not effecting the driving from anything I can tell. Still accelerates fine and I don't feel any loss in power. But the CEL sure is annoying to look at!

 

Did some more looking and it seems the S60's had a recall in '04 over the Fuel Rail Sensor that is throwing the code. Replacing seems to help them, though most people report stuttering etc. in conjunction with this. Looks like if I replace the sensor and the fuel filter (for good measure, doesn't hurt) I could kick this.

I'll report back when I replace the sensor and let y'all know what comes of it.

 

I've never seen a faulty fuel pressure sensor on a V8 (not to say it isn't possible). You'll need to remove the intake manifold, as it's buried under it. I really think you're dealing with a fuel level sensor issue, or a pump issue.

 

If it were a fuel level sensor or pump then why would it still show accurate levels in the tank (it goes below 1/4) and only stalls during high heat stop/go traffic (which is when I guess these units tend to fail). To me, if it were a fuel level sensor or a pump wouldn't there be more hesitation on acceleration, rough idles etc. rather than evap emissions and fuel rail pressure codes and only 2 stalls during stop/go traffic after an hour of 70mph driving (hot engine).

From what I understand the fuel level sensor and pump are more difficult to get to, I can get the sensor at napa for $80 and replace in probably 20 min. so why not try that first since that's what threw the error? I'm not shooting down your suggestion that it could be that, just trying to step through this as logically (and with the least cost of time/money) possible.

 

If it were the pressure sensor, you would have issues whether the tank is full, empty, or anywhere in between. My suspicion about the level sensor was based on you stating that you have issues at 1/4 tank, but I don't think you had mentioned that the gauge will drop further - in that case you can probably rule out the level sensor.

The evap codes are completely unrelated to your stalling problems.

 

So the CEL is back, tank is above half, checked again and it's a p0193 making me think it's still the sensor. The only thing is I'm not experiencing any of the normal signs to either part failing, no stuttering no power loss. Only stall happens when it's under 1/4 of a tank and in stop/go traffic after running for 1 hr. on the freeway (same congestion point ironically).

I'm swapping out the fuel filter tomorrow and putting in a tank of fuel injector cleaner. The sensor is 7-10 days out so it'll be 2 weeks before I can get that in.

Wouldn't a fuel pump cause power loss and stuttering in addition to the stall? The only time we've had any engine issues was the stalls, otherwise things are operating as normal.

Definitely a strange one indeed. Thanks for your help in thinking through it, let me know if anything else comes up I should look at. I'll keep y'all updated on how the filter/cleaner works.

 

Well thebracko you may be right here. I swapped out the fuel filter and put in a full tank of premium gas and some engine cleaner. Ran through the whole tank w/o any issues (even below the 1/4 full mark). After a few weeks the CEL randomly came back on. So I went and pulled the code again and it's a Pressure Regulator, fuel rail sensor, and evap emissions all tripped.

The guy said it's most likely the fuel pressure regulator that's letting it run too rich which is tripping the sensor and also the evap sensor. What do you guys think about this? Looking at the regulator it looks like it's in the pump assembly and probably going to have to drop the tank and replace. I have a feeling this is going to be PITA!

 

I'm looking all over and can't find where the pressure regulator is. I've read conflicting things that it's in the pump assembly but also that the pressure sensor is the regulator as well. Where is the pressure regulator located? If it's the sensor then swapping that out should clear 2/3 of my codes and hopefully cause the 3rd to clear on it's own.

Anyone have a VADIS printout of the fuel line? Thanks!

 

It doesn't have a traditional pressure regulator. This is an "on-demand" type of fuelling system. There is only a fuel feed line running from the pump to the fuel rail. The pressure sensor is what reads pressure, & the ECM tells the PEM (Pump Electronic Module) to adjust fuel pump duty cycle based on that signal, & other inputs. If you had VIDA, you would be able to read what the fuel pump duty cycle is - normal is 35% +/- 5%, and anything over 40% would LIKELY be telling you that the pump is working too hard to keep up with demand. You would be getting a specific pressure code, but I haven't a clue what those generic P codes correlate to with Volvo's codes.

 

Have you replaced the fuel filter? It's a 10 minute job on our cars. The filter is located right under the body right in front of the passenger side rear wheel. It has two quick release clamps on it. Squeeze it and have a drainage tank ready to catch the pressurized fuel, then a socket wrench to undo the bracket. Remove the old filter, then install the new one on the feed line, tilt the filter towards the waste jug and cycle the key a few times to prime the filter. Then bolt it all back up and hook the lines up. Cycle the keys a few times, and it might take a few tries to get the engine started the first time. Good luck.

 

Yeah I did that already (posted about it a couple posts back). I swapped out the fuel filter and ran a fuel additive/cleaner though just to blast anything that may be left by. I didn't prime the filter though (didn't know that was necessary) but it ran through a full tank w/o the CEL coming back on so I'm guessing that wasn't a must in my case.

After doing the filter I'm left at either the pump (large project) or the sensor (small project) that could be the options, at least from what I can tell. I may be missing something.