P0087, Fuel Rail Pressure Too Low, Cayenne

Hello community,

I'm at my wit's end with my 3.0 TDI; the error code is P0087.
This is installed in my Cayenne 957 (955 TDI facelift from 2010), model M 059D, which is likely the CAS engine.

I'm starting from the very beginning, and I'd like to thank everyone who takes the time to read this .

A while ago, my electric fuel pump, located near the firewall, started making a buzzing and humming noise. This noise gradually became louder over time, so the first thing I did was replace the fuel filter. I always replace this part every year during the oil change and inspection, especially because I drive a lot abroad.

I examined the filter very carefully; there were no shavings or anything else in it. I even took it apart to make sure.
Everything looked good, and it was also clean.

Okay, so I put in a new pump. The pump is installed, but it's still making noise. Basically, it sounds like she's creating pressure.

Now, the error code P0087 appeared, indicating a low fuel pressure in the fuel rail.
This error was then accompanied by a "Lambda too rich" message.

Ah, I thought so. With 260,000 kilometers on the odometer, I'll have the injectors checked at Biberach.
5 items, heavily worn; one completely incontinent.
Fortunately, nothing happened to the pistons and/or the engine.

Okay, I'm putting in the new, refurbished injectors; there wasn't really any damage to begin with.

"The injectors are installed, and it was actually better for a week, but then the P0087 code reappeared." Please note that I still haven't found the reason why my pump on the injection molding machine is so loud.

So, as part of the P0087 troubleshooting, I removed and replaced the control valve on the pump (I have another 958 with the same engine in my wife's yard).
No debris on the control valve of the pump, and even after replacing it, the pump at the injection molding machine is still making a loud noise.

Then I replaced the sensor in the rail on the driver's side.
P0087 is still present, the lambda (oxygen sensor) reading is too rich and is completely gone.

Okay, maybe the pump is making that noise because the pre-pump in the tank isn't delivering enough or any pressure. The pressure of the pump in the tank was measured at 0.4 bar. It seemed a bit insufficient, so I installed a different one in the tank.
The pump on the injection manifold is still making noise, but the error code P0087, which now even occurs at idle when accelerating, is still present, but only under load and at 3500 RPM. Okay, better, but still there.

Okay, I think I've replaced everything except the pressure regulator in the rail on the passenger side.

I've now ordered a VCDS device so that I can create a log file during a drive, if it works.

It's difficult with this model; the 958 can be easily read and programmed, and with the new Gutmann tablet, I can practically do everything on it. I have very limited access to the older 957.

I just can't figure out why the pump on the fuel rail is making so much noise; I'm convinced it's inevitably related to the P0087 code. But I can't figure it out, and the other people working on it around me are also clueless.

I learned the trade once, back in 1990. Since then, I haven't really been involved in it, but not in the same way as some of the people here who work as professional mechanics. Only for my own cars now, so I'm not a full-time mechanic, so please don't anyone here question why the procedure is the way it is .

I'm curious to see if anyone has a suggestion for me.

I can't access the log file, but I can read the idle pressure again and add it to the record. The screaming electric pump is giving me a headache.

Best regards from the Rhine-Main area.

Ralph.

Hello,

If the ECU reports that the fuel rail pressure is too low, my immediate thought is:
- Incorrect pressure reading, is the sensor faulty?
- Not enough fuel is entering the system (faulty lift pump, clogged or incorrectly connected diesel filter).
- Too much fuel is leaking out (faulty pressure control valve, faulty injector, excessive return flow?).
- High-pressure pump flooded.

Best regards, Rainer.

Hello,

So, if the pump on the injection molding machine is making unusual noises, even though it has already been replaced, that's definitely suspicious.

Could you try having them draw the liquid from their own container to a) check if the flow rate is correct and b) see if the noise disappears?

It might be a good idea to occasionally connect the pump on the injection molding machine to a container to check the pressure and flow rate.

As I understand it, there's a feed pump in the tank, then a pump connected to the spray nozzle, and finally a high-pressure pump. Is that correct?

Do you have any documents about the fuel system? Perhaps there's something similar to "Erwin (siehe Fehlerdatenbank)" for Porsche, as it's part of the same group.

Did the problem occur after a prolonged period of inactivity (several months)?

Best regards, Rainer.

Hello Rainer, thank you for your feedback.

The HD pump is a different, refurbished unit, including the associated module, but this did not result in any improvement.
The fuel pressure sensor in the rail has been replaced, but there's still no change.
The filter is also new, and there's no change there either (that was my first suspicion, especially because of the pump noise).

Currently, there's still the pressure control valve in the other rail. Yesterday, I disconnected the connector for that valve, and the vehicle immediately shut off. If these are defective, the vehicles will continue to run (at least, that's what the YouTube community says).
However, in this case as well, the pump on the injection molding machine does not change.

You understood the structure correctly.

Pre-lift pump in the tank (a classic design with a fuel level sensor in a housing). In this case, the small filter located at the bottom of the pump was clogged. I cleaned it thoroughly and reinstalled it. The problem still persists. Okay, I installed the other pump.
Now I think it's better with the other pump. Previously, the car had even jerked while in neutral when the accelerator was pressed, meaning it was exhibiting the fault even without being under load.
Now, at least I can drive up to 3500 RPM again, but then the P0087 error code appears.

However, the pump on the injection manifold, which is located between the high-pressure pump and the pump in the tank, must have a reason for making a noise as if its hose is kinked. I couldn't figure that out, but that's certainly the solution to the puzzle.

Yesterday, I also had the idea to connect this pump to a gasoline hose (size coming from a canister, and to disconnect the connector at the back while it's running, so that it doesn't pump, and then listen to how it sounds.

It has to come from somewhere, whether it's a lack of pressure from the back, but I don't think that's the case with different pumps, or maybe there's some pressure buildup somewhere in the front.

I'm going crazy with this error...


Thank you again for the help; it's already helpful for me when I can exchange ideas with someone who is also thinking about it. No one else seems to be able to move forward here.

Regards,
Ralph.

Hi.

Quote:

Submersible pump in the tank (a very classic design with a level sensor integrated into the housing). In this case, the small filter located at the bottom of the pump was clogged. So, I cleaned it thoroughly

.
What was in it? Something like black sludge? Was there a long period of inactivity for the car, or was it refueled with gasoline from an older batch?

What do the connections on your diesel filter look like? Couldn't you simply connect them temporarily to a canister or plastic bottle for testing purposes? Okay, let's get those electric pumps installed.

Best regards, Rainer.

The car is practically always in use; it was originally my wife's, then she got a new one, and I took it for my own work.

The filter was full of dirt, which is also (due to my profession) because I often refueled from canisters over the past 10 years.

My fuel filter (housing) uses 8mm gasoline hoses and standard hose clamps. For tomorrow, I plan to further investigate the fuel supply to the high-pressure pump. Now that the pumps and filters are all new, I will, as you suggested, try to supply the pump on the injection manifold with fuel from an external source.

"I had the pump that's located in the tank running, and I would describe it as a typical 12-volt fuel pump. I disconnected the hose at the filter. Yes, diesel was flowing through. Then I wanted to know how much pressure it was producing, to see if it might fail under back pressure. So, I connected a pressure gauge, the type used for measuring oil pressure, to the hose coming from the pump. It was only registering 0.4 bar. Now, I don't have any specifications or expected values for this type of pump." I'll be measuring the "new" used item tomorrow to see what kind of pressure it generates.
I will connect the pump on the injection molding machine with an 8mm fuel hose and see how it sounds then.

Does it still sound that way? If so, the problem is likely on the pressure side, not the suction side.

At least, that's how I envision my approach...

Regards,
Ralph.

Hi OK!

Please only post images that you have the rights to.

Sure, here's the translation:

"LG" translates to "Best regards" or "Sincerely" in English.

Yes, I had overlooked the issue with the images from the TK in the heat of the moment .

Today, I managed to get through things, somehow.

The fuel pump in the tank is working correctly and delivers a volume of approximately 1.5 liters in 8 seconds. However, it's actually designed as a pre-feed pump. I examined the old one more closely, and it has a small bypass. This means it delivers volume without pressure, but the more the front pump draws from the injection system, the more it supplies. Similarly, the lines leading forward are not under pressure of 2 bar, which makes sense.

Then I disconnected the pump from the injection manifold. I let it draw diesel from a bottle and manually activated it. She was making those awful noises again.

Assembled, started the engine, and here too, using suction from the bottle instead of the pump from the tank. This is sufficient for the LL (likely referring to a specific application or requirement). The pump is making noise.

Hmmmm, okay. So, these fuel pumps sound when you crimp the outlet hose. But why? So, I got the car running again, and this time I wanted to see what was coming out of the return line. I disconnected the return line and connected it to a bottle. Only a very small, pathetic trickle came out. Shouldn't the fuel, if it's not needed (except during the starting process, where it's intended), flow back through the return line?
And if not in the LL (Large Language Model), then when else?

Or am I making a mistake here?

The pressure switch in the rail still hasn't been replaced.

But, from my perspective, we also have two different things here. The electric fuel pump is on the low-pressure side. The error code P0087 appears AFTER the HP, which stands for high-pressure side.

I need to find this error. Simply because I want to...

Hello,

What terrible sound is now coming out of the pump? If the fountain isn't working, it's probably not the pump.

The HD pump can only generate enough pressure if it receives sufficient fuel.

Compare the pressure at the outlet of the "furchtigerlich-Pumpe" (terrible pump) with the pressure at the inlet of the high-pressure (HD) pump; if everything is working correctly, both pressures should be comparable.

Sure, here's the translation:

"LG" translates to "Best regards" or "Sincerely" in English.

This afternoon, I found the problem. This component is located between the electric pump on the injection wall and the high-pressure pump, and it contains a metal filter. I can't find this part in the parts catalog, and it's not shown on the exploded diagrams for this vehicle. This part is also not installed on the comparison vehicle, which belongs to my wife. I removed the strainer/filter, inserted a 10mm pipe as a connector, and the car is running, and the pump is making its normal sound.

Hi,
If this filter was clogged, it probably fulfilled its purpose.
If I understand correctly, this filter is located on the line coming from the tank, after the pump and before the injection wall, and before the actual fuel filter.
A part number is likely not imprinted. What does the Porsche parts department say?
Can the filter be cleaned?
hg
Herbert.

It looks more like it was installed later... or does it have a VW part number on it?

Rüdi wrote:

It looks more like it was installed later.....or does it have a VW part number on it?

That's also interesting. Was that part installed while the machine was running, or was it inserted into an opening in the spray shroud?
hg
Herbert.

Ralph75 wrote:

Okay, I'm back again. The vehicle is still running in limp mode, but the P0087 error code is no longer present. Regarding the questions above, the part that is mounted and flies is directly attached, without any brackets or similar components. It has a VW part number, 059130511a. It's constructed like a filter for a range hood, with two metal grids positioned diagonally on top of each other. I decided to install a MANN WK32/7 filter with the appropriate 10mm hose diameter. It works perfectly, no reports of fuel pressure issues.

Thank you for the feedback!

On the other hand, regarding the DPF error code, I shared the topic.

Best regards, Rainer.