My "08 CayenneS has 135K. I was on an extended trip towing my 19' Airstream from So Cal to Iowa. On the second day started to notice the gas smell outside and even while driving.... when I got cell service, I found the probable cause being the fuel filter.... I ordered a new fuel filter and 2 rubber seals and had delivered to my destination in Iowa.

Sure enough, the fuel filter was bad. It had developed a crack on the plastic dome of the filter and was leaking gas. Replaced and all is good until 2 weeks later.... I went from Iowa thru the Badlands, Custer Memorial at Little Bighorn, Mount Rushmore, a week at Yellowstone and 2 days at Grand Teton.... I filled with gas in Jackson, WY and proceeded the journey to Provo, UT...

Well somewhere just short of Heber, UT the Cayenne started losing power, I thought transmission problems, but it then come back with power and I managed to nurse it into Heber. My Durametric yielded P2632, Fuel Pump B Control Circuit/Open and one for High pressure fuel fluctuation and one more for fuel pump B ...(there are 2 more codes for MAF P1083 & P1094)

Now, I thought it's probably fuel pump related, however, when I pull fuses 13 & 14 the engine starts on either one..... Filled the tank in Heber, drove to Provo (no problems) topped off the tank and started the journey to St George, UT .... around 1/2 tank started to loose power intermittently again. Stopped and added 5gal (carried for generator) and we drove into Cedar City and fueled, now being sure to refuel just before 1/2 tank. Tried to stretch the distance a little and at 1/2 tank started loosing power again, add 5gal and continued.

So the dilemma is what is starving the fuel at 1/2 tank? One test I want to perform is when this happens, pull fuses 13 & 14 to see if there is any affect.
Any Ideas?

Also: I didn't see any change in fuel mileage

 

Funny, (but not really funny), I was towing a camper last week and had the same issue. I'm betting your problem gets worse and turns into feeling like it's running out of gas. Try this... if you start to lose power, go to full throttle (or close to it), does it pull strong and smooth?

I'm replacing both fuel pumps and fuel filter this week (parts arrive wednesday) to resolve. Mine started out as mild power loss and over several hundred miles turned into full on bucking, acting like it's out of gas.

 

No, the engine just shuts down, no throttle response, then suddenly comes back on. It's being starved of gas, my best guess.

 

One of your fuel pumps is failing. It's the one that pumps fuel over the center tunnel into the other side of the tank so the other pump can deliver it to the engine. I would bet if you keep the tank above 1/2 full you never experience the issue. Should be info on this site about how to test that and which one to replace as I've not had to do that myself yet.

If it happens over half full, it's the other primary pump or the HPFP used with the DFI motor.

 

I had the similar issue but mine was acting up below 3/4 tank while climbing high mountain passes. Yes, I've tried pulling fuel pump fuses one at a time but it made no difference, so HPFP was most likely the issue. I replaced all 3 fuel pumps and the problem went away when I did the same mountain passes again.

replace your HPFP, it's what's most likely causing it. If your in tank fuel pumps are original, replace those as well as a preventative maintenance.

 

Makes no sense that the issue is the HPFP, especially since this only happens at the 1/2 tank.

 

You already stated you had some codes related to high pressure fuel thing in the first post. Don't remember the exact algorithm that it uses when to run both fuel pumps but when you have a weak HPFP and when it's being supplied by one pump issues may pop up, especially in hot weather at high altitudes.

If pulling 13 / 14 makes no difference when this happens then that's where I would look.
Just checked the HPFP price on a V8 and just wow. Might be worth it to have a reputable shop to check the fuel pressures with the proper tools before shelling out 1K+ on a HPFP.
If you still have the original in tank fuel pumps you should probably replace them first, as a preventative maintenance and also to rule them out.

 

If the code reappeared, I might look at the HPFP, however the problem happened 2-3 times after reset code and it never returned. If FP doesn't deliver enough fuel to HPFP, then I would expect a pressure fluctuation and set a code. The HPFP runs on one FP almost all the time. AFAIK, only 2 pumps at startup.

I hope its not the HP.

 

Hey Glen, interesting timing on your post. Last week I drove to my in-laws in St. George and just south of Provo the same thing happened to me. 1/2 tank, car cut out and sputtered. I was close to an off-ramp so I took it and started to panic a little bit. I was close to a fuel station so I pulled in and filled it up. No CEL, which I thought was strange. I remembered reading about fuel pumps so I looked up the issue and then pulled fuse 14 under the hood. Car started and ran fine so I decided to chance it for the next 200 miles down to St. George. Car worked like a champ. I was able to hook up a basic reader the next morning and no codes. Car would start and rev just fine with fuse 14 back in and 13 then pulled. In short, I called and talked with my mechanic as well as a dealer in Vegas. Both confirmed that the right/passenger fuel pump is going out. Nobody had time to fix it as we were heading to Lake Tahoe 2 days later and after getting reassurance from 2 mechanics and other internet folks who had been in my same position, I decided to keep fuse 14 pulled and drove to Tahoe and then back to Boise with zero issues. I need to order both fuel pumps under the rear seats as the car now has 99k (I have an 09 CTTS).

You don't have an HPFP issue. I had one of those in my last Cayenne and even on a full tank, the car won't really rev over 3500 rpm. That's how you know it's a HPFP issue. Your symptoms are exactly like mine and it's one of the fuel pumps. I dove deep into this issue to find out why pulling a fuse would fix an issue and apparently because the Cayenne's have 2 tank pumps, they work together to balance things out (lift pump). Once one is going bad, if you pull the fuse, the computer reads that there is only one pump and then acts like a standard pump in any other vehicle.

Not sure this made much sense and it's too late to re-read for clarity, but order both fuel pumps and you'll be all good.

Cheers!

 

"going out" that is the key .... I read one post where they stated it's not if the pumps fail, it's when they fail.... Good to hear you were able to continue.
I haven't had a chance to try driving with fuse 14 pulled, however I have new fuel pumps ordered. With 135K miles, it just seems like replacing the pumps is preventative maintenance and reducing the chance of getting stranded with my Airstream in the middle of nowhere!

 

At 135K miles and no pump change, consider that a long, well-lived life for the pump. The fuel pumps do fail, similar to the drive shaft bearing. They can last longer by keeping your tank full. They are cooled by the fuel and if you're running tanks low, they can't keep themselves submerged and cool. Best of luck to you on the change. I'm going to tackle that soon myself.

Cheers!

 

Exactly, the driveshaft bearing went at 108500 and I fixed it with the pieces of rubber hose method and is working fine. New water pump, thermostat and epoxy coolant pipes at 108k.

 

Since you've an 09 CTTS, can you note any issues that you may encounter during the RR? My CTTS is @105k and I don't see any record of them ever being changed.

TIA

 

@TRINITONY I haven't done the R&R yet but I watched it being done on my prior GTS. It doesn't look too difficult, that's why I'm going to tackle it myself. I've got the parts list and will be ordering this week. I stupidly filled the tank the other day so it will take me a week or two before it goes down low enough to go after it. There is no difference between any 957 Cayenne models in terms of R&R-ing the in-tank pumps. It's just some time and attention but there is nothing on the CTTS that will cause a problem or interference more than a base model. Now taking off the intake manifold is another issue altogether! I'll report back once I've done it but it will be a couple weeks.

Cheers!

 

Same thing has just started when at 1/3rd to 1/2 a tank. HPFP came with the donor motor at 73k miles. I knew the fuel pumps would be a 'service soon' item and plan on starting with the right side, then the left. I will google it, but as I think outloud I sure hope the fuel filter isn't a pain. :-)