Intermittent Power Loss: Fuel Pressure Issues in 2.0 TDI?

Good day.

Okay, I'm stuck right now... My Octavia RS TDI occasionally has no power and doesn't accelerate properly, but there are no error codes stored in the diagnostic system! However, what I noticed from the live data is that all the target and actual values are correct except for the target value for fuel pressure.

Under full load at approximately 3000 RPM, the target pressure is around 2000 bar, but the actual pressure is only 1700 to 1800 bar. According to Volkswagen's self-diagnostic program, the CR engine should also have a pressure of 1800 bar. I can't understand how this significant discrepancy arises!

The vehicle has approximately 80,000 km on the odometer and received a new fuel filter from an original equipment manufacturer about 5,000 km ago. It has also only ever been fueled with gasoline, and it does not have any aftermarket tuning chips. Additionally, it has undergone the VW software update (related to the emissions scandal).

Regarding my actual question, how does this happen? Is the actual pressure reading normal even if it deviates significantly from the target pressure? Or is it actually the cause of the problem? If it's not normal, I suspect the control valve on the pump, because the valve on the rail only seems to work harder during startup and when regulating temperature, but less so afterward.

Has anyone had any experience with that before?

Vehicle data:
Skoda Octavia RS Estate.
2.0 CR TDI
MKB:CEGA
Year of manufacture: 2011.

Sure, here's the translation:

"I will send you an excerpt from the 'Autoscan' report."

Hello,

"Please run a full system scan. I find it hard to believe there would be an error entry related to a difference in rail pressure, but you never know..."
A low rail pressure can be caused by a worn high-pressure pump, a faulty fuel pressure control valve, or leaks in the fuel system.
Leaks are more likely to be ones where air is being sucked in instead of fuel; otherwise, your car would probably have already caught fire.
A faulty fuel filter or a malfunctioning vent in the gas cap can also be contributing factors.

Best regards, Rainer.

At this mileage, the pump shouldn't be worn out yet; as mentioned before, it has two control valves! I can also imagine that after reprogramming, the pressure might have been limited to 1800 bar in order to reduce nitrogen oxides in the exhaust? Therefore, this would be normal. What I'm interested in is how this deviation occurs??? Unfortunately, I don't have a second CR-TDI to compare it to . Maybe someone else does?

I think I'll check if the control valves are being activated when the regulating valve goes to 100% actuation. If that happens, it shouldn't be able to generate any more pressure, which would then indicate leaks, wear, or air in the system...

Best regards,
Christian.


Here's the car scan:
Sunday, June 25, 2017, 17:59:18:05381
VCDS – A VAG/VAS emulator based on Windows, running on Windows 10 x64.
VCDS version: RKS 17.1.3.0
Data as of: 20170505 DS267.9
http://shop.dieselschrauber.de


Vehicle Identification Number (VIN): TMBUH61Z4B2087953 License plate: HEI-XX 000
Mileage: 80640 km Repair order:



"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein perfekter Tag für einen Spaziergang."
"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein perfekter Tag für einen Spaziergang."


Vehicle type: 1Z (7N0)
Scan: 01 03 08 09 10 15 16 17 19 25 2E 42 44 46 52 55 56 62 72

Vehicle Identification Number (VIN): TMBUH61Z4B2087953. Mileage: 80,640 km.

01-Motor electronics -- Status: OK 0000
03-Brake electronics -- Status: OK 0000
04-Steering angle sensor -- Status: OK 0000
08-Climate control/heating unit - Status: OK 0000
09-Central Electrical System -- Status: Error 0010.
Parking Assist System 2 -- Status: OK 0000
15-Airbag -- Status: OK 0000
16-Wheel steering electronics -- Status: OK 0000
17-Terminal block insert -- Status: OK 0000
19-Diagnosis interface -- Status: OK 0000.
Immobilizer system -- Status: OK 0000
2E-Media Player 3 -- Status: OK 0000
42-Door Electric Driver -- Status: Error 0010.
Steering assist - Status: OK 0000.
46-Comfort System -- Status: OK 0000
52-door electric passenger door - Status: OK 0000.
55-Beam adjustment. -- Status: OK 0000.
56-Radio -- Status: OK 0000
62- Door, electric, left and right -- Status: OK 0000
72-Door, electric, high, right side -- Status: OK 0000.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 01: Engine Control Module (ECM)
Label file: DRV\03L-906-022-CBA.clb
Part number SW: 03L 906 022 RD, HW: 03L 906 022 GA.
Part: R4 2.0L TDI G000SG 9977
Revision: 13H14--- Serial number:
Encoding: 0000072
Operating number: WSC 52740 002 1048576
VCID: 78F86B630BC64E81D1-802C

No error codes found.
Readiness: 0 0 0 0 0

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 03: Brake Electronics (J104)
Label file: DRV\1K0-907-379-60EC1F.clb
Part number SW: 1K0 907 379 BE, HW: 1K0 907 379 BE.
Component: ESP MK60EC1 H31 0108
Revision: 00H31001
Encoding: 143B601C092A0001281406E9901C0042350800
Operating number: WSC 73430 790 00066
VCID: 76E4655BC1D238F1C3-8022

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 08: Climate Control/Heating Unit (J255)
Label file: DRV\5K0-907-044.clb
Part number SW: 3T0 907 044 BE, HW: 3T0 907 044 BE.
Component: Climatronic H16 0402
Revision: 00005001
Encoding: 0000000002
Operating number: WSC 73430 790 00066
ASAM Dataset: EV_Climatronic A01010
ROD: EV_ClimaAutoBasis_SK35.rod
VCID: 76E4655BC9D238F1C3-8022

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 09: Central Electronics (J519)
Label file: DRV\1K0-937-08x-09.clb
Part number SW: 1K0 937 087 J, Hardware number: 1K0 937 087 J.
Part number: BCM PQ35 H 103 0615.
Revision: 00103 AD
Encoding: 40000AB8C00308C040080080510091E4437000AE737D8560808540040040
Operating number: WSC 73430 790 00066
VCID: 3878AB638B468E8111-806C

Subsystem 1 - Part number: 1Z1 955 119 D
Label file: DRV\1KX-955-119.CLB
Part number: Wiper blade 09121 26 0601.
Encoding: 00DF97

Subsystem 2 - Part number: 1K0 955 559 AH
Label file: DRV\1K0-955-559-AG.CLB
Component: RLS 091210 05 54 0403
Encoding: 0730ED

"One error found:"
00061 - Footwell lights.
010 - Short circuit after positive terminal.
Environmental conditions:
Error status: 01101010
Error priority: 5.
Error frequency: 81
Lost Count: 152
Mileage: 78775 km
Time: 0.
Date: 2011.11.03
Time: 21:50:40

Environmental conditions:
Class 15, entry.
Voltage: 13.95 V
one
one
Size: 50, SOLD OUT.
text
from
text
from


"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 10: Parking Assist 2 (J446) Label file: DRV\5J0-919-475.clb
Part number SW: 5J0 919 475 A, Hardware part number: 5J0 919 475 A.
Component: PARK ASSIST 4K H11 0005
Revision: --H11--- Serial Number: 32991034423633
Encoding: 10000F
Operating number: WSC 13765 790 00066
ASAM Dataset: EV_EPHVA14SKxxx0000 001001
ROD: EV_EPHVA14SKxxx0000.rod
VCID: 33629C4F9A206DD924-8066

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 15: Airbag
Label file: DRV\1K0-909-605.lbl
Part number SW: 1K0 909 605 T HW: 1K0 909 605 T
Part number: Q6 AIRBAG VW8, 020 2300.
Revision: 05020000 Serial number: 0038PC225L2.
Encoding: 0020790
Operating number: WSC 73430 790 00066
VCID: 3D76BA776464ABA9C2-8068

Subsystem 1 - Serial number: 6332MSME5962135EG

Subsystem 2 - Serial number: 6342MSME59644A70H.

Subsystem 3 - Serial number: 6351HSME250A196FF.

Subsystem 4 - Serial number: 6361HSME25050D3EA.

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 16: Steering wheel electronics (J527)
Label file: DRV\5K0-953-569.clb
Part number SW: 5K0 953 521 BL, HW: 5K0 953 569 C.
Component: STEERING MODULE 009 0136
Revision: FF010039 Serial Number: 20101214100169
Encoding: 5080140000
Operating number: WSC 73430 790 00066
ASAM Dataset: EV_SMLSNGVOLWS A01004
FILE: EV_SMLSNGVOLWSXS.rod
VCID: 77FA685FCED841F9D8-8022

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 17: Control panel module (J285)
Label file: DRV\5K0-920-xxx-17.clb
Part number SW: 1Z0 920 843 N, HW: 1Z0 920 843 N.
Component: COMBINATION H20 0420
Serial number: 00000000000000
Encoding: 110F01
Operating number: WSC 73430 031 00066
ASAM Dataset: EV_Kombi_UDS_VDD_RM09 A04089
ROD: EV_Kombi_UDS_VDD_RM09_004_VW25.rod
VCID: 4382CC8FCA80DD59B4-8016

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 19: Diagnostic interface (J533)
Label file: DRV\7N0-907-530-V2.clb
Part number SW: 7N0 907 530 C, HW: 1K0 907 951.
Component: J533 Gateway H37 0614.
Revision: H37 Serial Number: 081210F2002484
Encoding: 352302
Operating number: WSC 73430 790 00066
VCID: 30689343633656C159-8064

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 25: Immobilizer (J334)
Label file: DRV\5K0-920-xxx-25.clb
Part number SW: 5K0 953 234, HW: 5K0 953 234.
Component: IMMO H20 0420
Serial number: 00000000000000
Encoding: 000000
Operating Number: WSC 00000 000 00000
ASAM Dataset: EV_Immo_UDS_VDD_RM09 A03008
ROD: EV_Immo_UDS_VDD_RM09_VW21.rod
VCID: 6ADC412B8D6AEC1157-803E

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 2E: Media Player 3 (J650)
Label file: DRV\5N0-035-342.lbl
Part number SW: 5N0 035 342 D, Hardware part number: 5N0 035 342 D.
Component: SG EXT.PLAYER H13 0150
Revision: A1001003 Serial Number: 7668987487
Encoding: 010000
Operating Number: WSC 00000 000 00000
VCID: 28587B235BE61E0181-807C

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 42: Door electric driver
Label file: DRV\1K0-959-701-MIN3.clb
Part number SW: 1T0 959 701 T HW: 1T0 959 701 T
Component: Door seal 009 2119
Encoding: 0000244
Operating number: WSC 73430 790 00066
VCID: 4898DBA33BA6FE0161-801C

"One error found:"
00932 - Power window motor, driver's side (V147)
005 - No or incorrect initial setup/adjustment.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 44: Steering Assist
Label file: DRV\1K0-909-14x-GEN3.clb
Part number: 1K0 909 144 J
Component: EPS_ZFLS, Size 74 3001
Revision: 00H17000
Operating number: WSC 73430 790 00066
VCID: 316E9647A83C5FC956-8064

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 52: Door electronics, passenger side.
Label file: DRV\1K0-959-702-MIN3.clb
Part number SW: 1T0 959 702 R. Hardware: 1T0 959 702 R.
Component: Door seal 009 2119
Coding: 0002292
Operating number: WSC 73430 790 00066
VCID: 479AD89F36B8F17968-8012

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 55: Headlight range control. Label file: DRV\5M0-907-357-V2.lbl
Part number SW: 5M0 907 357 C. Hardware: 5M0 907 357 C.
Component: AFS Control Unit 0148
Revision: 00H04000 Serial Number:
Encoding: 1507354
Operating number: WSC 73430 790 00066
VCID: 34609F53572E6AE13D-8060

Subsystem 1 - Part number: 7L6 941 329 B
Label file: 3D0-941-329.CLB
Component: AFS-List Module l 0004
Encoding: 00000023

Subsystem 2 - Part number: 7L6 941 329 B
Label file: 3D0-941-329.CLB
Component: AFS-List Module r 0004
Encoding: 00000023

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 56: Radio (J503) Label file: DRV\5M0-035-1xx-56.clb
Part number SW: 1Z0 035 161 G, HW: 1Z0 035 161 G.
Component: Radio-SWING 011 0034
Revision: -----15S Serial number: SKZ4Z2K1421958
Encoding: 0D0004000001
Operating number: WSC 73430 790 00066
VCID: 326C994B6D3A64D12F-8066

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 62: Door electrics, left and right. Label file: DRV\1K0-959-703-GEN3.clb
Part number SW: 5K0 959 703 A, Part number HW: 5K0 959 703 A.
Component: Door Seal 007 2101
Encoding: 0000144
Operating number: WSC 73430 790 1012546
VCID: 326C994BAD3A64D12F-8066

No error codes found.

"Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein wunderschöner Tag."

"The sun is shining brightly and warmly. The birds are chirping happily in the trees. A gentle breeze is blowing through the grass. It's a beautiful day."
Address 72: Door electric strike, right side.
Label file: DRV\1K0-959-704-GEN3.clb
Part number SW: 5K0 959 704 A, HW: 5K0 959 704 A.
Component: Door Seal 007 2101
Encoding: 0000144
Operating number: WSC 73430 790 1012546
VCID: 33629C4F52206DD924-8066

No error codes found.

End----------------------------(Duration: 02:14)-----------------------------

Even after the update, the actual value should reach the target value. The essence of a software change is to adjust the target values.

Measure the pressure of the pre-pump and check if it's actually running.

Good evening , I would need to measure the pressure of the pre-lift pump at the company, or can it be displayed in VCDS, or is it monitored?

Since the actual pressure is always 200 to 300 bar below the target values and reacts slowly, I removed the mass airflow sensor (MAF) and drove in limp mode. Ironically, it has more power, and the fuel pressure also builds up much faster. However, interestingly, it only reaches a maximum target pressure of 1800 bar under full load instead of over 2000 bar! The question is now, can the mass airflow sensor overestimate or underestimate in a range that the engine control unit doesn't recognize as an error? I'm starting to feel like I'm going crazy . The question is, should it even run at 2000 bar, since according to official VW documentation, the injection pressure is limited to a maximum of 1800 bar? So far, I'm ruling out a defect in the high-pressure pump, because it builds up the pressure much faster in limp mode than with the MAF sensor connected.

Does anyone know what the maximum pressure is that a CEGA motor should operate at in high-pressure mode? Is it 1800 or 2000 bar?

Best regards,
Christian.

The mass airflow sensor (MAF) readings seem slightly off, but I would still consider them to be within the acceptable tolerance range (less than a 30 mg/h deviation). However, it reacts sluggishly to changes, with a delay of approximately 1-2 seconds.

Hi,

Please fix your "Shift" key; it's currently acting like a random number generator and needs to be reset every time.

Quote:

Does anyone know what the maximum pressure is that a CEGA motor should run at in high-pressure operation? 1800 or 2000 bar?

Learn what a feedback loop is and how it works. A naive question: the setpoint is the value that the motor should run at (the name already suggests it).

If the engine runs worse with the mass airflow sensor (MAF) (target rail pressure is higher) than without the MAF (resulting in a limp mode, possibly with a reduced target rail pressure), then the MAF is not causing the problem, but rather the deviation between the target and actual rail pressure!

Could it be that you have a poorly executed tuning modification in the engine control unit?

Best regards, Rainer.

Thank you for the response . No, this vehicle has not been tuned, neither through a chip nor with a tuning box.