XC90 V8 Intermittent fuel pressure cutout (kinked fuel pump line) Topic is solved

Post by **SHOCKWAVE** » 03 Jan 2018, 15:37

Hi,

New to Volvo cars (2007 XC90 V8 Sport, 151k mi)! Already need some help...

BACKGROUND: FUEL PUMP/ LEVEL SENDER replaced 6 months ago by previous owner.
ISSUE: Fuel pressure intermittently drops leading to a non-responsive throttle or engine stall. Only happens after 20+ minutes of driving. It has happened at idle, slow speed, and freeway speeds. I have been able to plug in a WI-FI OBD reader when this is occurring and the fuel pressure is dropping from 480kpa/500kpa to 200/300 kpa. It bumps back up every 5 seconds or so, but it wouldn't go up from 200/300 kpa when I had it towed. When running "normally" the car drives "heavy" like there isn't as much power as there should be. But this car is new to me...
RESOLUTION WHILE ON THE ROAD: Toggle the throttle to get a response back or turn it off and restart it. Also, filling up with gas seems to help. 1 time I had to get it towed. 1 time I was close to home and limped home. The other 3 times, I was able to limp to a gas station.
FREQUENCY: Has occurred 5 times over 800 miles.
SUSPECTED CAUSES: I initially suspected an incorrect fuel gauge calibration, but it has occurred with 1/4 tank of gas, 3/8 tank, and 7/8 tank.
CURRENT RESOLUTION: Keep throttle low 1.5k to 2k rpms to avoid heavy loads on the engine/system.
ATTEMPTED FIXES/DIAGNOSIS(Issue Not Resolved): Replaced FUEL FILTER, AIR FILTER, SPARK PLUGS, FUEL PRESSURE SENSOR (FPS). Noticed a 3.2 engine PN for the old FPS, not sure if that had any ill effects. I tested with carb cleaner and only found a leak at the TB gasket. That will be replaced when it arrives in the mail. Also, I'm not sure if the engine should sound like this or not (possible vacuum leak)

OTHER CAUSES?: PEM/FCU? I'm not sure what else to look at...I'd rather avoid the stealership. I have VIDA/DICE on the way, so maybe that will help some. Also, I am planning on other PM such as MAF cleaning. The TB and Plenum looked fairly dirty and could use a clean, but I'd like to know what is causing the fuel pressure to drop in half intermittently. Any ideas/recommendations? Here is some live data at idle:

Thanks for any advice!
//EDIT-CHANGED IMAGES TO ONE FILE AND REMOVED ANALOG PIC//

Post by **cuhfs** » 04 Jan 2018, 18:06

Any updates?

Post by **SHOCKWAVE** » 05 Jan 2018, 12:33

@cuhfs- Thanks for the view/inquiry.

I received my DICE unit yesterday and I'll try to get it running this weekend. TB Gasket comes on Monday. I will pull the back seat and inspect the PEM this weekend for corrosion (SoCal car, so doubtful). I'm driving very slow (<2k rpm) until this gets figured out to try to avoid the issue.

This thread seems to have members with similar symptoms: viewtopic.php?f=10&t=72213&hilit=clogged&start=10

and somewhat similar here (my issue is more intermittent than this one): https://volvoforums.com/forum/volvo-xc9 ... 511/page2/

and here: https://volvoforums.com/forum/volvo-xc9 ... sue-89252/

so...

I'm thinking of these possibilities:
1) Vacuum leak- TB Gasket + maybe something else
2) Dirty Tank- clogging fuel pump screen on greater acceleration https://volvoforums.com/forum/volvo-xc9 ... 534/page2/ see post #32 -#34
3) Kinked fuel line (maybe when the fuel pump was replaced)
4) PEM/FCU issue
Possible but not likely:
5) Dirty intake paths (throttle body, plenums)
6) Dirty MAF
7) ECM on the fritz... no other symptoms so very unlikely

Planned fixes this weekend/Monday:
a) Throttle body gasket
b) Clean throttle body and accessible parts of plenum
c) Clean MAF (CRC MAF Cleaner)
d) Re-check for vacuum leaks
e) Inspect PEM (I don't have the fuel pump tool, so I can't get in there yet to check while I have it accessible)
f) Magnet on the bottom of fuel tank

I am confused by the fact that it runs fine and then out of nowhere (it seems), fuel pressure gets cut in approximately half. That can be at partial throttle or sitting at a stop light. It also returns briefly to normal if I shut the car off and turn it back on. Filling up with fuel seems to help when this situation occurs. I've been driving it since the last occurrence (12/30/17) with light throttle and it hasn't happened again.

I'll update as I go... Any input is always appreciated... Please comment on the sound in the video if you have a V8 if that sound is normal when revving... I had a BMW 540i V8 that had breathing problems and I had to replace all the upper gaskets. Maybe this one needs it...

Post by **cuhfs** » 05 Jan 2018, 13:53

If you are speaking about the creak/squeak sound no that does not sound normal - but does not sound serious either. Sounds like something needs a shot of WD40. I do have a 06 XC90 V8.

Post by **SHOCKWAVE** » 06 Jan 2018, 19:27

The sound is actually not a squeak, but the plenum filling with air. It sounds like blowing over the top of a bottle but much “deeper”. Only happens when the throttle is opened quickly and the sound dissipates immediately. That has me suspecting the plenum gaskets. I shot carb cleaner everywhere I could, but didn’t get any change in rpm other than TB gasket. Parts came in today so I’ll replace the TB gasket and see if there are any noticeable differences. Not sure if I can get VIDA running anytime soon as I don’t have a machine with the proper specs. Illl update as the saga continues... advice and input always appreciated!

Post by **Roger_850T** » 07 Jan 2018, 09:20

I heard your video - I'm still trying to decide if I'm concerned by it, but I don't think it's the cause of your issue. I'll have to listen to mine and see if I hear the same sound.

You indicate that the "FUEL PUMP/ LEVEL SENDER replaced 6 months ago by previous owner" - is this the in-tank level sensor that drives the gas gauge?

Your trouble code "P0089 Fuel Pressure Regulator Performance" is one I've been getting, too, although I haven't had the drivability issues you have. I've been learning that the fuel pressure sensor can be problematic. I have a new sensor, but haven't put it in yet.

The ECU modulates the speed of the fuel pump with a Pulse Width Modulation (PWM) signal. It sets this code when the value indicated by the fuel pressure sensor does not match what the ECU calculates it should be (within a range). If the code is set, it falls back on the calculated value to run the engine.

VIDA indicates the possible sources are:
- Air in the fuel lines
- Blocked fuel lines
- Damaged fuel pressure sensor
- Damaged fuel pump
- Damaged fuel pump control module

with fault symptoms:
- Malfunction Indicator Light (MIL) lit
- Poor performance
- Engine stops

I don't have any of the other threads about the fuel pressure sensor handy - hopefully you can find them. It's found across a number of different vehicles, not just the V8 XC90. It would be worthwhile to look into.

If you decide to replace it, you will also need the two gaskets for the intake manifold parts - you have to disassemble the manifold to reach the sensor. (That's why mine's not done yet - had to place a second order for the gasket...)

If you want to get more sophisticated in your troubleshooting, you can dig into where the problem really is: Is it that the fuel pump is providing the right pressure and the pressure sensor is wrong, or is the pump not providing the right pressure, and the sensor is accurately reporting the fuel pressure?

Do you know why the prior owner had the fuel pump replaced? Was it chasing down this same problem?

I hope this helps!

Roger

Post by **SHOCKWAVE** » 08 Jan 2018, 11:36

@Roger- Thanks for the info.

ANSWERS-
-FUEL PUMP/ LEVEL SENDER- Yes, this is the in tank sender
-Prior owner (PO)- See attachment. The pump/sender unit was replaced in March by an outside shop which subsequently failed again...then replaced by Volvo.
-FPS replaced by me so the issue is most likely a vac leak, something in the lines, or debris in the tank from what I can tell.

NOTES ON COMMENTS:
Thanks for the info on the control logic. If I understand, the FPS is only used to detect an issue with supply and not as an input parameter to control/modify supply. That means the ECU is lowering the pump output (e.g.- forces it to run lean due to too much air from a vac leak) or something is intermittently restricting the flow. Bumping the throttle and/or turning off/restarting is the emergency techniques I've used to get me home (and/or topping with fuel).

FPS- I did replace that without removing the plenum (http://forums.swedespeed.com/showthread ... Code-P0089, see Post #19). You have to set the position of the FPS and blindly put the screw in. You just cup your fingers around the plenum. Just takes patience. Using a sharpie or white out to mark the position of the FPS to it's mount point before removing may help. I checked the PN of the existing one and it was for a 3.2 engine. (NEW-IS: 0261230110 (V8), EXISTING-WAS: 0261230238 (3.2).) I contacted Bosch and they wouldn't comment on the differences between the two PN's so I don't know if that was an issue.

REPAIR: This weekend:
1) Went to install a new TB gasket and discovered that I had only hand tightened the nuts/screws on the TB when I replaced the FPS = vacuum leak at TB. I'm not sure if a vac leak would cause the engine to freak out enough to cut fuel pressure in half under load...intermittently... maybe.
2) Put a 65 lb pull magnet on each of the fuel tank straps. Possibly to keep debris away from the pump if present.
3) I'll have to stop babying it to see if the fixes are working. I can probably only test on weekends, because I don't want to get stranded on my commute. Eventually, I think I'll have to inspect the tank and/or lines so I can find the root cause of this issue.

Post by **Roger_850T** » 08 Jan 2018, 13:47

I think that it does use the fuel pressure sensor for closed loop control of the fuel pressure, but when it detects a significant discrepancy, it falls back to open loop control and disregards the pressure sensor. I think my problem is the pressure sensor, so mine still runs pretty well open loop, while yours has an actual fuel delivery issue, which is why yours stalls and runs poorly. This could be confirmed by connecting an external fuel pressure sensor (connect to Schrader valve on fuel rail).

The question then is why is it failing to deliver fuel.

Do you have VIDA/DiCE? Or just the Bluetooth-to-phone version? The ECM will actually take a snapshot of all the other values at the time the trouble code is set, which can be seen with VIDA/DiCE.

It's possible that there is something in your tank that is blocking the fuel suction. Or maybe a slug of water in there. That will just sit on the bottom of the tank and float around and get sucked in occasionally. Although that wouldn't cause the pressure to fall; it would just be water instead of fuel that goes through the system.

Assuming that the pump was replaced with a good pump...

...and assuming that the ECU is sending a good signal to the pump controller... The next thing to suspect would be the pump controller. Or the wiring. I'd probably look at that before looking for kinks in the fuel line. A kink would be unlikely to be intermittent.

I'm trying to think about how to test the pump controller. (Short of driving around with an oscilloscope on it...) You could probably at least inspect and see if anything looks awry, corroded, or otherwise obviously an issue. I'll see if I can find any better description of what that signal should look like. (I know it's PWM, but I suspect that might be PWM from the ECU to the controller, not the controller output.) When possible, I'd much rather measure and find the problem first!

Roger

Post by **SHOCKWAVE** » 12 Jan 2018, 14:31

-I've driven 150 miles without the issue arising, but I've been staying under 2k rpm.
-I have the bluetooth OBD which I used previously to get some info. Typically pressure fluctuation trying to stay at about half of normal (200kpa versus 480kpa) when the issue occurs.
-I will try to get VIDA installed/running. Hopefully I can get it going this weekend. The electrical disk was included so I'll see if I can get some info from that as well.
-Rented a pressure test kit, so I can try to get some information from the test ports (fuel rail and fuel filter ports)
-I'll update when I have more information. Unfortunately for testing, I think I have to push the system harder to get (+3k rpm/extended drive time 20mins). Fortunately, if I don't push the system (<2k) it seems to run "ok". At least it doesn't cut/throttle fuel supply.

@Roger_850T- Did you replace your FPS? It's pretty straightforward by just moving the TB aside.

Post by **mrbrian200** » 12 Jan 2018, 17:12

The fuel pump has been changed unnecessarily (probably both times) without anyone, including the second time at the dealer, keying into the problem being elsewhere. It's the PEM (most likely) or the wiring. The PEM is not on the CAN network. The control signal from the ECU->PEM is a one way communication. If the PEM, fuel pump, or the wiring to either has a problem, the ECU has no way of knowing and will only spit out anecdotal DTCs, such as low or no fuel pressure.

The PEM regulates the fuel pressure as variable. Around 60psi during start/crank and hard throttle. Low to mid 40s at warm idle in park. If it stops responding to the control signal from the ECU (mine did this) it'll sit around 43-45psi (~300kpa) at idle, lower while driving.