Need help diagnosing high pressure fuel pump issues

Hello, I'm Danny.

I've attached a picture below with the fuel pressure specification. You should verify this first. Does your Foxwell have the same capabilities as the PIWIS tester? Let us know and we'll go from there. I've attached the specification below. Hope this helps and thanks for using 2CarPros.

I just went through every menu, no fuel pressure reading on pids... grrr

I did find fuel rail psi on my torque app. At cold start it was low, then 350psi at idle, average 550 PSI at 50 MPH, downshifts brought 800 PSI.

Tiny bit confusing though, when you go to graphing it adds a zero, so watching the graph for 40 minutes, it went from 5,500 to 8,000 on downshift, 3,500 at idle.

I don't know what to think, when it coughed, i saw no drop.

Hello,

Your vehicle has 2 fuel systems, a pre-supply system from 2 in tank fuel pumps which will supply a low pressure of around 5-5.5 bar. These are the values my colleague gave earlier.
The high pressure part of the fuel system is regulated by the high pressure fuel pump mounted at the right rear of the cylinder head. For the DFI system the fuel pressure ranges from around 40 bar at idle to around 120 bar under full load.

I would suggest to start by checking the actual supply pressure from the in tank fuel pumps. Connect a manual fuel gauge to the supply line and start the engine. Check that the pressure is at around 5-5.5 bar or 50-55 PSI. Please see attached picture below for the supply line location.

How to check the supply pressure, the below You-Tube is for a VW Tuareg V8. This also applies to your vehicle,

https://youtu.be/ZVBaH2jsPg4

Also see our instruction.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Looking at the values you provided the scan tool seems to give live data values for the high pressure side, using the rail pressure sensor. The readings are possibly on the low side as 3,500 PSI at idle is on the lower side. The fuel pressure increases when there is more load on the engine but 8,000 PSI seems too low, we should see more than 100-120 PSI. This could be caused by either the pre-supply side being low or the mechanical high pressure pump being faulty.

Please let us know how you get along.

Cheers, Boris

I started watching the misfire counters and cylinder 6 is all over the place. When i did the PCV, the coil in cylinder 6 was practically fused in there with some sorta pink powder (i'm guessing dried coolant) I dug it out, blasted it out with air, and changed the plug, after removing all the... whatever it was. I then reassembled the coil and it ran fine since.

Now i have the random misfires on 6.

I'm thinking i have 2 separate issues. I have ordered new coils, a new hpfp and new seal kits for the lower 3 injectors that have to be removed when the manifold comes off. I have read that once disturbed they have a chance to leak.

I don't want to do this again.

Hi,

It has been a few days since we heard from you. Have you been able to make any progress? We're interested in knowing if the problem has been resolved.

Let me know.

Take care,

Joe

I will be doing all the work this weekend, had to wait for parts and tools.

Hi,

Thanks for the update. Let us know if there is anything we can do to help.

Take care,

Joe

Did the coils today at lunch. #6 fell apart. Registering 0 misfires now. I will see what happens under load on my way home.

Hi,

I suspect you found the problem. Let me know if it runs properly after the drive home.

Take care,

Joe

Well, it's running perfectly, but I still have a random raw fuel smell. Before the coils it was at every stop sign, traffic light and i couldn't park and idle.

Now, with it running better, it's super random. Started it last night, no smells whole ride home. Same with sitting in my driveway, last night and this morning, nothing. Got to work, there it was. Out to lunch, nothing. Got home, no smell. Now i'm out on the town and it happened once out of the multiple stops. I'm sitting here stopped in a parking lot, idling, no smell.

Turned it off, sat for 2 minutes, restarted engine, there's the smell, but it leaves in less than a minute.

Still no MIL, no misfires, just a random smell.

If it's running well, I question if there is a small evap leak. Did you check the charcoal canister, purge valve, and hoses?

Joe

That's where i'm going next. I did replace a line recently that comes from the tank, to the intake manifold and the vacuum pump (3way nylon hoses with a check valve).

It kind of makes sense as well. I only smell it when it's hot (tank pressure), and it comes in the vents, not from under the seats.

You may want to consider having the EVAP system smoke tested. Basically, smoke is injected into the system at very low pressure. If there is a leak, it usually can be seen. It's a thought.

Let me know if you find it. I'm interested in knowing.

Take care,

Joe

It's a tool i need in my arsenals, i keep putting it off, and paying to have it done. I know they are expensive but i have seen some diy made ones.

Hi,

They can be expensive. I agree. On the other hand, as you mentioned, I have heard of people making things that worked as well. I'm not sure how it would be done, but they seem to work.

Let me know if I can help in any way.

Joe

Well, there is a whole 2 lines from the tank, the feed and the evap line.

I think when the windshield was replaced, they disturbed the evap line. I separated it, cleaned it and reseated it until it clicked.

No more smells. I guess it's time to return the tools and parts.

Hi,

Was there evidence of them damaging the evap lines?

Regardless, if the problem is now fixed, that's great news. Please feel free to come back anytime in the future if you have questions. You're always welcome here.

Joe

Not damaged, but looks like unhooked and not completely seated back together. They were popped out of the clips on the firewall.

That will do it. I'm glad you noticed it.

Take care of yourself and please feel free to come back anytime in the future. You're always welcome here.

Take care,

Joe

And the smell is back, got to smoke the system. What the heck?

Hi,

Sorry to hear that. I read back through everything. Are you certain there isn't an injector leaking? Have you tried a leak-down test on the fuel system?

Let me know.

Joe

Is that possible on a high-pressure fuel system? I have no access to any of the injectors without removing the intake manifold.

And wouldn't that happen each and every time, a leaking injector wouldn't stop on its own i would imagine.

Hi,

It's possible. You don't have to remove the injectors to check if there is a leak somewhere in the system. You will need to perform a fuel pressure drop-off test. First, start the engine and allow pressure to build. Then, see how quickly it drops when the key is turned off.

Here is what the manufacturer indicates:

2.1. Same tool setup and connection as for measuring the fuel delivery pressure (see above).
2.2. Allow engine to run for a few minutes. Switch off engine. Check the pressure drop. Drop in fuel pressure after "ignition is switched off" must not exceed 1 bar after 1 hour. Make sure that the tool setup itself does not have any leaks (even the slightest leak). The fuel retaining pressure will decrease extremely rapidly and falsify the measured result with even the tiniest leak.

This will at least identify if there is a leak.

Let me know what I can do to help.

Joe

Well, today i took everything back apart. I found a damaged O-ring on injector 4. Plus, a telltale of dried fuel below it. Replaced all three O-rings, lubed liberally, and reassembled. I also put in a new HPFP at the same time, just cause i don't want to do this again.

Success, no more smell.

Excellent!!! I'm glad to hear you found the problem. Isn't it funny how the smallest part can cause the biggest problem? LOL

Regardless, give yourself a good pat on the back from me for a job well done. Also, please feel free to come back anytime in the future if you have questions or need help with something. You're always welcome here.

Take care of yourself,

Joe

Here is a link to the Porsche forum I'm in and the thread i made with instructions:

https://rennlist.com/forums/cayenne-955-957-2003-2010/1272350-2nd-time-removing-the-intake-on-my-3-6-vr6-957-heres-what-i-learned-sorry-no-pics.html

Nicely done. That was a lot to do. Again, feel free to come back anytime in the future.

Take care,

Joe