2.0 TDI CR CBBB engine: Fuel pressure below specification (up to 440 bar)

Hello everyone,

"I've been experiencing power loss issues with my Volkswagen Passat Variant 2.0 TDI CR CBBB 170HP, manufactured in 2009, with approximately 295,000 km on the odometer, including a "defeat device" software update."

Recently, I purchased KDataScope so that I could properly display the values.
You can find the recording in the attachment.

I immediately noticed a very large discrepancy between the target and actual values for fuel pressure.

Symptoms I can describe include a lack of power, especially noticeable with a cold engine, and a very strained throttle response and power delivery.
There is nothing related to this issue in the error memory.

Could the high-pressure pump perhaps need to be replaced given this mileage?

Hello,

Quote:

Ist die Hochdruckpumpe bei dieser Laufleistung vielleicht reif gewechselt zu werden?

Possible candidates include the pressure regulating valve and, more generally, the fuel supply system.

If the high-pressure pump is worn, the difference between the target pressure and the actual pressure should be lower at high speeds than at low speeds.
The same applies to a pressure regulating valve that does not seal properly.

With insufficient fuel supply (due to a clogged filter or leaky hoses), the car would experience progressively decreasing performance as the engine speed and load increased.

Have you checked the fuel return at the injectors (individually) and compared them to see if they are all working correctly?

Best regards, Rainer.

I don't have it (yet).
I'll try to put something together tomorrow using four PET bottles and a hose, and then I'll let you know how it turns out.
Thank you for your assessment.

Okay, I was finally able to check the return flow volume of the injectors (at idle), and in my opinion, everything looks good here.

I also removed and inspected the pressure regulating valve on the high-pressure pump to see if there were any metal shavings present, but I didn't find any.

I would now also like to check the return flow rate under load, as shown in the following video: https://www.facebook.com/autohausguempelein/videos/1510271845815425/

Hello,

Quote:

Bei ungenügender Kraftstoffzufuhr (verstopfter Filter, undichte Schläuche) würde das Auto mitsteigender Drehzahl und steigender Last leistungsmässig immer mehr abbauen.

Checked already? The diesel filter would be my first suspect.

Regarding the high-pressure pump, there seems to be at least a market for it; a search for "CBBB fuel injection pump" immediately yielded results for spare parts. Perhaps other forum users have experience with this issue?

Best regards, Rainer.

Good evening.

When I look at the KDataScope graph, it appears that the fuel pressure drops during acceleration. Afterwards, it stabilizes again within the normal range.

Why isn't an error message logged in the control unit when the sensor measures insufficient pressure?


Have you been experiencing these problems for a while? Does this describe the period since it has become noticeably colder?

What does the fuel temperature sensor say? Does it provide realistic values?


Then there were two issues regarding fuel with the Passat 3C.
"I cannot determine if your vehicle is affected based on the missing VIN."

You might be able to find the corresponding stickers either in the trunk compartment or in the service booklet.

Action 92B6 Fuel cooler bracket.
(Loose connection / Fuel leak)

Action 20R6 Diesel filter.
(Manufacturing defect / leaky)


The other potential sources of error are already listed above.





Michael.

I suspect no error entry is being made because the values are still within a tolerance range. However, I don't know what those tolerances are. At least, there is no stored error related to fuel pressure or something similar.

"For a longer period of time" means since the beginning of last year. However, initially, the problem was a faulty pressure sensor on the turbocharger, which caused the engine to go into limp mode at a certain RPM.
After that, I always felt like the car wasn't performing as it should. Since I've been driving this car since approximately 28,000 kilometers, I have a good sense of what the expected performance should be.
There is a correlation with temperature only in relation to the engine not being warmed up. When the engine is still cold, it runs even worse.

Regarding the promotions, I will look into it and get back to you. Thank you.

Tomorrow I will change the fuel filter and then the search continues.

Quote:

Morgen werde ich den Kraftstofffilter wechseln und dann geht die Suche weiter.

Possibly, you could cut open the filter and check for metal shavings... I certainly hope not, but it makes sense given the mileage.

Best regards, Rainer.

After removing and examining the fuel filter more closely, I found exactly five thin, elongated aluminum shavings. Therefore, I suspect that I have been affected by the flawed high-pressure pump design from Bosch?

If the chips were caught in that location, is it sufficient to just replace the high-pressure pump (HD), or does a full procedure need to be performed (including flushing)? Since no chips were found below the control valve on the HD (i.e., towards the engine), what's the best course of action?

Hi,

Given the mileage and the fact that the diesel filter has been replaced several times before, it's likely that these are actually metal particles that accumulated during normal operation.

Perhaps you have already checked the values of the idle speed control system to see if they are unusual (background: possibly due to debris clogging the nozzle openings).

If the low-pressure fuel rail (LLR) appears normal, flushing the system and replacing the high-pressure pump might be a worthwhile approach. However, there's no guarantee; we can only speak of probabilities. If the LLR is functioning correctly, it's likely that the injectors are still in good condition.

If the nozzles/injectors (and possibly other components like the pressure control valve or the fuel rail) also need to be replaced, the vehicle can quickly reach a point where it's no longer economically viable to repair, considering the mileage.

Best regards, Rainer.

Hi there,
Do we have any comparison images of debris from a faulty high-pressure pump? While the observations point towards a high-pressure pump or fuel metering valve, the shape of the debris shown reminds me more of chips produced during thread cutting or drilling (perhaps from opening the filter?).
hg
Herbert.

When I was replacing the fuel filter the other day, one of the screws actually broke off, and I had to drill out the remaining piece.
So, it's possible that something might have fallen into the funnel (which I forgot to mention earlier).
I will review the LLR and report back.

Sure, go ahead...





I think Herbert's assumption is very good and likely.


From my experience, the shavings also look different...

It's like starting all over again.

The variations in quantities are within the normal range.

Hi there,
The volume deviations of the LLR are almost negligible, provided that measurements were taken at idle and as close to operating temperature as possible. The return flow volumes also appear uniform, although the total volume is missing for idle conditions and at 2000-2500 rpm (specifically, 50 ml or 250 ml for the CJCD).
Under load, the rail pressure is regulated via a valve for fuel metering in the high-pressure pump. However, before you start troubleshooting the high-pressure pump, there are still some things you can check.
- check the fuel system low pressure.
or
- Check the flow rates of the pre-pump and the auxiliary fuel pump. The RLF (Reparatur- und Wartungsanleitung - Repair and Maintenance Manual) for your engine will tell you whether you have both pumps or only one, and how to check them precisely.
If the high-pressure pump doesn't deliver enough pressure, the valve won't be able to function properly either.
You can also check the fuel pressure regulator valve.
The details depend on your engine. I only have documentation for the CJCD from 2014. However, the structure should be similar.
There's also a filter screen in front of the high-pressure pump. Perhaps we can check it for shavings as well.
hg
Herbert.