2010 Audi Q7 3.0 TDI - P0087

   #1  

jmjq7tdi

Verified VCDS User
Verified
Joined
Sep 15, 2015
Messages
39
Reaction score
22
Location
Lidingö, Sweden
VCDS Serial number
C?ID=205446
Hello all,
I'm hoping you can help me avoid an expensive trip to the repair shop. Huge thanks in advance. Beginning yesterday, the flashing glow-plug light started coming on and putting the Q7 in limp mode. It did this for the first three consecutive trips yesterday morning. It ran fine otherwise during those trips, even though it was in limp mode, limiting me to about 80km/hr. The next three trips later that day, it ran normally, no glow plug light came on at all. One of those trips was to the auto parts store, because I knew that three of the glow plugs were already throwing error codes regularly and I had the same issue with my previous Q7. Then, last night (before I had a chance to install the glow plugs), my wife took it out, and both the check engine and the flashing glow plug light came on, so she returned home and took a different vehicle.

Today, before even scanning for codes, I took it for a long drive to warm it up, but never drove too fast. The flashing glow plug light eventually came on again, but no check engine light. It ran remarkably smooth and well. I took it home, replaced all six glow plugs, and also, since I was working on it anyway I also replaced the fuel filter.

The old fuel filter looked very good, the fuel inside the fuel filter canister was remarkably clean, and there was no grime or deposits in the bottom of the canister.

I ran VCDS to collect a new log and to clear the codes. I didn't pay much attention to the codes that were coming up because the first three codes were all old glow plug codes and I thought this work would clear them. I cleared all the codes, and proceeded to take it out for the verification test drive. Within one block, the flashing glow plug light came back on again (but no check engine light). I ran the codes again, checked with the previous codes before clearing it, and saw that a low fuel pressure failure P0087 appeared in both the before and after. But at least the glow plug errors are gone.

I've been doing a lot of research, and it seems that there are many possible culprits. Worst case scenario would be the HPFP, but as clean as the fuel filter canister was (I rechecked the filter and don't see any specs of metal at all), it didn't seem as if the HPFP was self-destructing or anything. I removed the pressure control valve from the top of the HPFP because I saw several pictures that showed metal underneath it when an HPFP fails, but it was perfectly clean inside, and surprisingly this valve already has the strainer mounted on it, so another good sign that the HPFP is probably not eating itself as I've seen in so many of the pictures online - but I understand that doesn't mean I can rule it out.

Other possible culprits would seem to be the high pressure sensor or the fuel pump(s) in the tank. Maybe the fuel pump pressure control valve mounted on the HPFP? I don't know, but I haven't found any other examples of that being the problem.

How should I approach this diagnostic - without a mechanical fuel pressure gauge?

Here's the latest scan. Thanks in advance for your help!

Code:
Thursday,09,April,2020,17:30:33:49964
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 19.6.2.2 (x64)
Data version: 20200210 DS308.0
www.Ross-Tech.com


VIN: WAUZZZ4L3AD0#####   License Plate: 
Mileage: 158560km-98524mi   Repair Order: 



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Chassis Type: 4L (4F0)
Scan: 01 02 03 05 08 09 13 15 16 17 18 19 20 28 34 36 3C 42 46 47
          4F 52 55 56 5F 62 69 6C 6D 6F 72 76

VIN: WAUZZZ4L3AD0#####   Mileage: 158560km-98524miles

01-Engine -- Status: Malfunction 0010
02-Auto Trans -- Status: OK 0000
03-ABS Brakes -- Status: OK 0000
04-Steering Angle -- Status: OK 0000
05-Acc/Start Auth. -- Status: OK 0000
08-Auto HVAC -- Status: OK 0000
09-Cent. Elect. -- Status: OK 0000
13-Auto Dist. Reg -- Status: OK 0000
15-Airbags -- Status: OK 0000
16-Steering wheel -- Status: OK 0000
17-Instruments -- Status: OK 0000
18-Aux. Heat -- Status: OK 0000
19-CAN Gateway -- Status: Malfunction 0010
20-High Beam Assist. -- Status: OK 0000
28-HVAC, Rear -- Status: OK 0000
34-Level Control -- Status: OK 0000
36-Seat Mem. Drvr -- Status: OK 0000
3C-Lane Change -- Status: OK 0000
42-Door Elect, Driver -- Status: OK 0000
46-Central Conv. -- Status: OK 0000
47-Sound System -- Status: OK 0000
4F-Centr. Electr. II -- Status: OK 0000
52-Door Elect, Pass. -- Status: Malfunction 0010
55-Headlight Range -- Status: OK 0000
56-Radio -- Status: OK 0000
5F-Information Electr. -- Status: OK 0000
62-Door, Rear Left -- Status: OK 0000
69-Trailer -- Status: OK 0000
6C-Back-up Cam. -- Status: OK 0000
6D-Trunk Elect. -- Status: OK 0000
6F-Centr. Conv. II -- Status: OK 0000
72-Door, Rear Right -- Status: Malfunction 0010
76-Park Assist -- Status: OK 0000
 
-------------------------------------------------------------------------------
Address 01: Engine (CAS)       Labels:. 059-907-401-CAT1.clb
   Part No SW: 4L1 910 401 D    HW: 4L0 907 401 A
   Component: 3.0TDI EDC17A104AG  0080  
   Revision: --H02---    Serial number:               
   Coding: 0121002C191F0A68
   Shop #: WSC 40970 222 94360
   VCID: 2447ED83E718D36FE1-8070

1 Fault Found:
000135 - Fuel Rail/System Pressure 
               P0087 - 003 - Too Low
             Freeze Frame:
                    Fault Status: 01100011
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 158567 km
                    Time Indication: 0
                    Date: 2020.04.09
                    Time: 17:21:32

             Freeze Frame:
                    RPM: 1575 /min
                    Speed: 3.4 km/h
                    Mass Air / Rev.: 36.0 mg/str
                    Temperature: 48.6°C
                    Pressure: 795.2 bar
                    (no units): 5.0
                    Bin. Bits: 00110100

Readiness: 0 0 0 0 0 

-------------------------------------------------------------------------------
Address 02: Auto Trans        Labels: 09D-927-750.clb
   Part No SW: 09D 927 750 KC    HW: 09D 927 750 KC
   Component: AL 750 6A           1470  
   Revision: 00H78000    Serial number:               
   Coding: 0000504
   Shop #: WSC 31414 790 00001
   VCID: 79F9ECF7301A7E87E2-802C

No fault code found.

-------------------------------------------------------------------------------
Address 03: ABS Brakes        Labels:. 4L0-910-517-V2.clb
   Part No SW: 4L0 910 517 K    HW: 4L0 614 517 K
   Component: ESP ALLRAD MK25E1   0020  
   Revision: 00H30001    
   Coding: 0627841
   Shop #: WSC 31414 790 00001
   VCID: 326B1BDBADEC4DDF63-8066

No fault code found.

-------------------------------------------------------------------------------
Address 05: Acc/Start Auth.        Labels:. 4F0-910-852.clb
   Part No SW: 4F0 910 852 B    HW: 4F0 905 852 D
   Component: FBSAUDIC6 ELV   H05 0100  
   Revision: 00H05000    Serial number: 10602601405096
   Coding: 0000135
   Shop #: WSC 31414 790 00001
   VCID: 2541F087EC222A67F6-8070

   Subsystem 1 - Part No: 4F0 910 132 G
   Component: FBSAUDIC6 EZS   H03 0020

   Subsystem 2 - Part No: 4F0 910 335 B
   Component: FBSAUDIC6 KSG   H03 0020

   Subsystem 3 - Part No: 4F0 910 220 K
   Component: FBSAUDIC6 IDG   H01 0040

No fault code found.

-------------------------------------------------------------------------------
Address 08: Auto HVAC (J255)       Labels: None
   Part No SW: 4L0 910 043 C    HW: 4L0 820 043 AB
   Component: KLIMA 4 ZONEN H12 0030  
   Revision: 00---017    Serial number: 00000000212367
   Coding: 040816
   Shop #: WSC 31414 790 00001
   VCID: 2447ED832718D36FE1-8070

No fault code found.

-------------------------------------------------------------------------------
Address 09: Cent. Elect.        Labels: 4F0-910-279.lbl
   Part No SW: 4F0 910 279 R    HW: 4F0 907 279 
   Component: ILM Fahrer      H25 0330  
   Revision: 00000000    Serial number: 4F0907279     
   Coding: 0033221
   Shop #: WSC 31414 790 00001
   VCID: 387F29F34B90A78F5D-806C

   Subsystem 1 - Part No: 4L1 910 113   Labels: 1KX-955-119.CLB
   Component: Wischer AU716   H17 0100  
   Coding: 00064792
   Shop #: WSC 31414  

   Subsystem 2 - Part No: 8K0 910 557   Labels: 8K0-955-559.CLB
   Component: REGENLICHTSENSORH04 0003  
   Coding: 00150059
   Shop #: WSC 31414  

No fault code found.

-------------------------------------------------------------------------------
Address 13: Auto Dist. Reg        Labels: None
   Part No SW: 4L0 910 561 A    HW: 4L0 907 561 
   Component: ABSTANDSREGELUNGH06 0160  
   Revision: --------    Serial number: 00000000000000
   Coding: 0031161
   Shop #: WSC 31414 790 00001
   VCID: 275DFA8F962E3877C4-8072

No fault code found.

-------------------------------------------------------------------------------
Address 15: Airbags        Labels: 4L0-910-655.lbl
   Part No SW: 4L0 910 655 D    HW: 4L0 959 655 C
   Component: 70 AIRBAG AUDI8RH43 0230  
   Revision: 04H43000    Serial number: 00399D065B3G  
   Coding: 0014128
   Shop #: WSC 31414 790 00001
   VCID: 2E530FABB9D4693F07-807A

   Subsystem 1 - Serial number: 6332QSME623A191AH

   Subsystem 2 - Serial number: 6342QSME703A32067

   Subsystem 3 - Serial number: 6352QSME4338322CE

   Subsystem 4 - Serial number: 6362QSME623A143AH

   Subsystem 5 - Serial number: 63734SME3136050EX

   Subsystem 6 - Serial number: 63834SME2F364400-

No fault code found.

-------------------------------------------------------------------------------
Address 16: Steering wheel        Labels: 4F0-910-549.lbl
   Part No SW: 4F0 910 549 A    HW: 4F0 953 549 D
   Component: J0527               0530  
   Revision: 00H05000    Serial number: 90026092380094
   Coding: 0002052
   Shop #: WSC 31414 790 00001
   VCID: 275DFA8F962E3877C4-8072

   Subsystem 1 - Part No: XXXXXXXXXXX 
   Component: E0221           H02 0030

No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments (J285)       Labels:. 4L0-920-xxx-17.clb
   Part No SW: 4L0 920 931 J    HW: 4L0 920 931 J
   Component: KOMBIINSTR.   H08 0144  
   Revision: 00000000    Serial number: CNN432799     
   Coding: 0F5E63040C010008000000
   Shop #: WSC 31414 790 00001
   VCID: 326B1BDB6DEC4DDF63-8066

No fault code found.

-------------------------------------------------------------------------------
Address 18: Aux. Heat        Labels: 4L0-910-105.lbl
   Part No SW: 4L0 910 105     HW: 4L0 265 105 M
   Component: Heizgeraet      H08 0120  
   Revision: 0000000E    Serial number: 00000009014264
   Coding: 0000101
   Shop #: WSC 31414 790 00001
   VCID: 60CFA193B3808F4FC5-8034

No fault code found.

-------------------------------------------------------------------------------
Address 19: CAN Gateway (J533)       Labels:. 4F0-907-468.clb
   Part No SW: 4F0 907 468 N    HW: 4F0 907 468 G
   Component: GW-BEM 5CAN-M H06 0035  
   Revision: MB200030    Serial number: 3000M098308025
   Coding: 000303
   Shop #: WSC 31414 790 00001
   VCID: 3A7B33FBB59CB59FAB-806E

   Subsystem 1 - Part No SW: 8K0 915 181 D    HW: 8K0 915 181 D
   Component: J367-BDM  H07 0107 
   Serial number: 00000000004140159397

1 Fault Found:
00470 - Company Comfort Databus in Single Wire 
            011 - Open Circuit
             Freeze Frame:
                    Fault Status: 01101011
                    Fault Priority: 3
                    Fault Frequency: 2
                    Reset counter: 110
                    Mileage: 158567 km
                    Time Indication: 0
                    Date: 2020.04.09
                    Time: 17:03:54

             Freeze Frame:
                    Bin. Bits:    11111
                    Voltage: 14.60 V
                    Count: 7
                    Bin. Bits:    10011


-------------------------------------------------------------------------------
Address 20: High Beam Assist. (J844)       Labels:. 8K0-857-511.clb
   Part No SW: 4F0 857 511 J    HW: 4F0 857 511 G
   Component: FLA           H04 0004  
   Revision: AA001002    
   Coding: 02019064747464545425363E
   Shop #: WSC 31414 790 00001
   VCID: 2F6D12AF7EDE60370C-807A

No fault code found.

-------------------------------------------------------------------------------
Address 28: HVAC, Rear        Labels: None
   Part No SW: 4L0 910 158     HW: 4L0 919 158 AB
   Component: KLIMABETAETIGUNGH06 0060  
   Revision: 00---010    Serial number: 00000000352325
   Coding: 0000006
   Shop #: WSC 31414 790 00001
   VCID: 68DFB9B35BB0F70F0D-803C

No fault code found.

-------------------------------------------------------------------------------
Address 34: Level Control        Labels: 4L0-910-553.lbl
   Part No SW: 4L0 910 553 H    HW: 4L0 907 553 
   Component: LUFTFDR.-CDC    H03 7870  
   Revision: --H03001    Serial number: 15.1528-0123.2
   Coding: 0015520
   Shop #: WSC 31414 790 00001
   VCID: 2F6D12AFBEDE60370C-807A

No fault code found.

-------------------------------------------------------------------------------
Address 36: Seat Mem. Drvr (J136)       Labels: None
   Part No SW: 4F0 959 760 C    HW: 4F0 959 760 C
   Component: MEM-FS        H08 0062  
   Revision: AA000000    Serial number: 00001001346979
   Coding: 00581B00000011110000
   Shop #: WSC 31414 790 00001
   VCID: 316914D768EA76C71A-8064

No fault code found.

-------------------------------------------------------------------------------
Address 3C: Lane Change        Labels: None
   Part No SW: 4L0 910 566 C    HW: 4L0 907 566 B
   Component: J0769_SWA_MasterH01 0040  
   Revision: 00H01000    Serial number: 6PZ 009 014-10
   Coding: 0010101
   Shop #: WSC 31414 790 00001
   VCID: 2E530FABB9D4693F07-807A

   Subsystem 1 - Part No: 4L0 910 568 C
   Component: J0770_SWA_Slave_H01 0040

   Subsystem 2 - Serial number: 6PZ 009 014-30

   Subsystem 3 - Serial number: 5F21.07.0900H010003C910745ÿ

   Subsystem 4 - Serial number: 910745ÿ

No fault code found.

-------------------------------------------------------------------------------
Address 42: Door Elect, Driver (J386)       Labels:. 4F0-959-793.clb
   Part No SW: 4F0 959 793 R    HW: 8K0 959 793 D
   Component: TSG FA        H11 0250  
   Revision:             Serial number: 0000101820752 
   Coding: 011F52205E40440004
   Shop #: WSC 31414 790 00001
   VCID: 4683570BF164C17FDF-8012

No fault code found.

-------------------------------------------------------------------------------
Address 46: Central Conv.        Labels:. 4L0-910-289.lbl
   Part No SW: 4L0 910 289 H    HW: 4L0 907 289 H
   Component: Komfortgeraet   H09 0100  
   Revision: 0100 ---    Serial number: 01219373360000
   Coding: 3549361
   Shop #: WSC 31414 790 00001
   VCID: 356120C75C825AE746-8060

   Subsystem 1 - Part No: 1K0 951 605 C
   Component: LIN BACKUP HORN H03 1301

No fault code found.

-------------------------------------------------------------------------------
Address 47: Sound System (J525)       Labels: Redir Fail!
   Part No SW: 4L0 035 223 E    HW: 4L0 035 223 E
   Component: BOSE G3 AU716 H01 0100  
   Revision: AH001500    Serial number: 00000000008395
   Coding: 0D000000
   Shop #: WSC 31414 790 00001
   VCID: 2447ED832718D36FE1-8070

No fault code found.

-------------------------------------------------------------------------------
Address 4F: Centr. Electr. II        Labels: 4F0-910-280.lbl
   Part No SW: 4F0 910 280     HW: 4F0 907 280 E
   Component: ILM Beifahrer   H13 0100  
   Revision:             Serial number: 00000000139275
   Coding: 0011101
   Shop #: WSC 31414 790 00001
   VCID: 5EB39F6B89F4B9BFF7-800A

No fault code found.

-------------------------------------------------------------------------------
Address 52: Door Elect, Pass. (J387)       Labels:. 4F0-959-792.clb
   Part No SW: 4F0 959 792 R    HW: 8K0 959 792 D
   Component: TSG BF        H11 0250  
   Revision:             Serial number: 0000101847220 
   Coding: 011F52205E40440004
   Shop #: WSC 31414 790 00001
   VCID: 45815007CC62CA67D6-8010

1 Fault Found:
02126 - Central Locking Button; Exterior Door Handle 
            008 - Implausible Signal
             Freeze Frame:
                    Fault Status: 01101000
                    Fault Priority: 3
                    Fault Frequency: 1
                    Reset counter: 110
                    Mileage: 158567 km
                    Time Indication: 0
                    Date: 2020.04.09
                    Time: 17:05:00


-------------------------------------------------------------------------------
Address 55: Headlight Range        Labels: 4F0-910-357.lbl
   Part No SW: 4L0 910 357 A    HW: 4L0 907 357 A
   Component: AFS 1           H01 0030  
   Revision: 00000001    Serial number:               
   Coding: 0000032
   Shop #: WSC 31414 790 00001
   VCID: 2A5B03BB853C051FDB-807E

   Subsystem 1 - Part No: 7L6 941 329 A
   Component: AFS-Modul links H07 0004

   Subsystem 2 - Part No: 7L6 941 329 A
   Component: AFS-Modul rechtsH07 0004

No fault code found.

-------------------------------------------------------------------------------
Address 56: Radio (R)       Labels: Redir Fail!
   Part No SW: 4F0 035 053 K    HW: 4F0 035 053 
   Component: Radio U Basic H45 0074  
   Revision: AB001007    Serial number: 341IZ097634851
   Coding: 010003010000000000
   Shop #: WSC 31414 790 00001
   VCID: 2541F0872C222A67F6-8070

No fault code found.

-------------------------------------------------------------------------------
Address 5F: Information Electr. (J794)       Labels:. 4E0-035-6xx-5F.clb
   Part No SW: 4L0 035 670 H    HW: 4L0 035 670 
   Component: H-BNT-EU      H41 0187  
   Revision: --------    Serial number: 474I6097515869
   Coding: 010100060004DBEF71000715EF6300030000
   Shop #: WSC 31414 790 00001
   VCID: 2D5108A774D212273E-8078

   Subsystem 1 - Part No: 8R0 060 884 ED
   Component: EUR 2017  2402 

   Subsystem 2 - Part No SW: 4F0 919 604     HW: 4F0 919 604 
   Component: DU7 High  H43 0306 
   Serial number: 9356IZ091064728     

   Subsystem 3 - Part No SW: 4L0 910 609     HW: 4L0 919 611 C
   Component: E0380 Bedient  H05 0060 
   Serial number: 00000001400099      

   Subsystem 4 - Part No: 8R0 906 961 A
   Component: CD-Database  1293 

No fault code found.

-------------------------------------------------------------------------------
Address 62: Door, Rear Left (J388)       Labels:. 4F0-959-795.clb
   Part No SW: 4F0 959 795 M    HW: 8K0 959 795 B
   Component: TSG HL        H10 0251  
   Revision:             Serial number: 0000101862201 
   Coding: 010E50204040230004
   Shop #: WSC 31414 790 00001
   VCID: 43854E1FC256F457F8-8016

No fault code found.

-------------------------------------------------------------------------------
Address 69: Trailer (J345)       Labels:. 4E0-907-383.clb
   Part No SW: 4E0 907 383 J    HW: 4E0 907 383 J
   Component: Anhaenger     H09 0100  
   Revision: 2A001001    Serial number: 00008200327685
   Coding: 0100000000000000
   Shop #: WSC 80093 222 69422
   VCID: 316914D768EA76C71A-8064

No fault code found.

-------------------------------------------------------------------------------
Address 6C: Back-up Cam.        Labels: 4L0-910-441.clb
   Part No SW: 4L0 910 441 B    HW: 4L0 907 441 B
   Component: J772__Rearview      0030  
   Revision: --H03---    Serial number: 525PA8-J9940CA
   Coding: 1021001
   Shop #: WSC 31414 790 00001
   VCID: 2541F087EC222A67F6-8070

No fault code found.

-------------------------------------------------------------------------------
Address 6D: Trunk Elect.        Labels: None
   Part No SW: 4L0 910 945     HW: 4L0 827 851 D
   Component: ValeoHeckdeckel H29 0410  
   Revision: --H29001    Serial number: 8K9827852  B  
   Shop #: WSC 98765 666 38354
   VCID: 6CD7C5A34F48DB2F69-8038

   Subsystem 1 - Part No: 4L0 910 946 
   Component: ValeoHeckdeckel H29 0410

   Subsystem 2 - Serial number: E5030100B     

   Subsystem 3 - Serial number: RD16.09.09--H29001001A0322ÿ

   Subsystem 4 - Serial number: 1A0322ÿ

No fault code found.

-------------------------------------------------------------------------------
Address 6F: Centr. Conv. II        Labels:. 4L0-910-290.lbl
   Part No SW: 4L0 910 290 A    HW: 4L0 907 290 A
   Component: ILM HINTEN 2    H05 0060  
   Revision: AAH05061    Serial number: 003881240-----
   Coding: 0003587
   Shop #: WSC 31414 790 00001
   VCID: 2643F78B9124217FFF-8072

   Subsystem 1 - Part No: 4L0 910 591 
   Component: J_245_EE16_SKB09H10 0200

   Subsystem 2 - Part No: 4L0 910 591 
   Component: J_394_EE16_SKB09H10 0200

   Subsystem 3 - Part No: 4L0 910 591 
   Component: J_392_EE16_SKB09H10 0200

No fault code found.

-------------------------------------------------------------------------------
Address 72: Door, Rear Right (J389)       Labels:. 4F0-959-795.clb
   Part No SW: 4F0 959 795 M    HW: 8K0 959 795 B
   Component: TSG HR        H10 0251  
   Revision:             Serial number: 0000101862200 
   Coding: 010E50204040230004
   Shop #: WSC 31414 790 00001
   VCID: 43854E1FC256F457F8-8016

1 Fault Found:
02126 - Central Locking Button; Exterior Door Handle 
            008 - Implausible Signal
             Freeze Frame:
                    Fault Status: 01101000
                    Fault Priority: 3
                    Fault Frequency: 1
                    Reset counter: 110
                    Mileage: 158567 km
                    Time Indication: 0
                    Date: 2020.04.09
                    Time: 17:06:36


-------------------------------------------------------------------------------
Address 76: Park Assist        Labels: 4Fx-910-283.lbl
   Part No SW: 4L0 910 283 E    HW: 4L0 919 283 E
   Component: Parkhilfe 8-Kan H02 0100  
   Revision: 00H02000    Serial number: 85130925303084
   Coding: 0231166
   Shop #: WSC 31414 790 00001
   VCID: 2C5705A38FC81B2F29-8078

No fault code found.

End-------------------------(Elapsed Time: 03:50)--------------------------
 
   #2  

Uwe

Benevolent Dictator
Staff member
Joined
Jan 29, 2014
Messages
31,185
Reaction score
22,214
Location
USA
VCDS Serial number
HC100001
I guess I would try to see what's going on in MVB Group 020, where you should find:
Engine Speed
Specified Pressure
Actual Pressure
Pressure Control Valve duty cycle

MVBs 018, 019, and 021 all have pressure-related info as well.

There are also some tips here:
http://wiki.ross-tech.com/wiki/index.php/16471/P0087/000135

-Uwe-
 
   #3  

jmjq7tdi

Verified VCDS User
Verified
Joined
Sep 15, 2015
Messages
39
Reaction score
22
Location
Lidingö, Sweden
VCDS Serial number
C?ID=205446
I've taken a brief look at the pressures in those MVB's, but not while driving around, just idling and revving the engine. In those cases, the specified pressure and actual pressure were always in sync. How should I go about getting useful information from these? I saw another post about low fuel pressure where he did some type of logging in VCDS, but I haven't tried that yet. Do I need to start logging and drive around?
 
   #4  

Jack@European_Parts

NostraJackAss
Joined
Jan 29, 2014
Messages
21,229
Reaction score
8,981
Location
Montgomery, NY, USA
VCDS Serial number
C?ID=57337
How should I approach this diagnostic - without a mechanical fuel pressure gauge?

Did you know you should not attempt such an approach with exception of rail isolation caps & while logging with VCDS to manage injector zones for comparison of actual PSI reported or a fuel filter changed?

RTFB should be observed for safe testing procedures fuel system and mechanicals cross referenced to log data.
 
   #5  

jmjq7tdi

Verified VCDS User
Verified
Joined
Sep 15, 2015
Messages
39
Reaction score
22
Location
Lidingö, Sweden
VCDS Serial number
C?ID=205446
That's what I'm concerned about - not being able to do much without any mechanical testing tools. I saw another post of yours where you posted a pic of these isolation caps. I don't even have a mechanical gauge for these kinds of pressures, so if it gets to a point where the diagnostics require that, I'm going to have to take it in to a shop. I'm hoping we can collect enough clues to narrow down the culprit.
 
   #6  

Jack@European_Parts

NostraJackAss
Joined
Jan 29, 2014
Messages
21,229
Reaction score
8,981
Location
Montgomery, NY, USA
VCDS Serial number
C?ID=57337
Did you know caps can be installed and PSI compared in logs of rail and if DTC goes away for PSI after cleared and PSI jumps up, than you know that's the respective problem injector like leaking down now don't you?
 
   #7  

Uwe

Benevolent Dictator
Staff member
Joined
Jan 29, 2014
Messages
31,185
Reaction score
22,214
Location
USA
VCDS Serial number
HC100001
I've taken a brief look at the pressures in those MVB's, but not while driving around, just idling and revving the engine. In those cases, the specified pressure and actual pressure were always in sync. How should I go about getting useful information from these? I saw another post about low fuel pressure where he did some type of logging in VCDS, but I haven't tried that yet. Do I need to start logging and drive around?
I suspect so. No-load conditions simply don't use much fuel.

-Uwe-
 
   #8  

jmjq7tdi

Verified VCDS User
Verified
Joined
Sep 15, 2015
Messages
39
Reaction score
22
Location
Lidingö, Sweden
VCDS Serial number
C?ID=205446
Did you know caps can be installed and PSI compared in logs of rail and if DTC goes away for PSI after cleared and PSI jumps up, than you know that's the respective problem injector like leaking down now don't you?
Okay, I hear you. We need to add the possibility of a leaky injector to the list of potential problems. Short of capping-off the supply lines for injectors, is there another way to determine if 'any' of the injectors are leaking? Since it's CR, if just one is leaking, the entire system should depressurize, right? I saw a diagnostic test where you monitor fuel pressure in VCDS after engine cutoff, and due to heat soak, it should theoretically rise a little bit. Would that same type of test apply to the 3.0 TDI?

Also, if I had an injector that was leaking that badly, i.e. exhibiting low fuel pressure by 2k RPM's, wouldn't I see smoke out of one side from the extra fuel? At least a little bit?

If 'any' of the injectors are leaking, is there any value in determining exactly which one, i.e. is it okay to only replace a single injector in a car with 98k miles and leave the rest alone, or should they all be removed and sent off?

About to head out now to start logging fuel pressures.
 
   #9  

jmjq7tdi

Verified VCDS User
Verified
Joined
Sep 15, 2015
Messages
39
Reaction score
22
Location
Lidingö, Sweden
VCDS Serial number
C?ID=205446
When starting it this morning for the first time, it seemed to have to crank over longer than unusual, maybe 5-6 seconds instead of the normal ~2 seconds of cranking before start. Every start after that, it starts right up. There was a slight hint of smoke from the right side exhaust of the car, but it was very, very light, probably just morning condensation burning off. It really didn't seem to be excess fuel.

So, I drove around for a while and logged 018, 019 and 020. Here's the logging info for MVB 020 at the specific point of failure. Not too surprising. When RPM's start to rise above 2000, fuel pressure can't keep up. At over 2500, the computer catches it and puts it in limp mode.

https://www.dropbox.com/s/tu2w632um9j4yqv/FocusedData.jpg?dl=0

Here's the graph for the entire drive. It seems that the fuel pressure generally keeps up with all demands except when RPM's go above 2000, or fuel pressure above 1250 bar.
https://www.dropbox.com/s/16j83maqcpefu95/EntireDrive.jpg?dl=0
 
Last edited:
   #10  

Dana

Administrator
Staff member
Ross-Tech Employee
Joined
Jan 29, 2014
Messages
4,343
Reaction score
6,369
Location
Western PA, USA
Using the gas Fuel Rail Pressure Test testing/logging method can be applied to a TDI however the failed part would need to be bad enough that you saw a complete leakdown under key on, engine off conditions. Since yours runs and just can't keep up under high RPM I'm not sure it will reveal problems. If this was a no-start or constant long-crank on startup that would be easier to spot.
 
  • Like
Reactions: Uwe
   #11  

jmjq7tdi

Verified VCDS User
Verified
Joined
Sep 15, 2015
Messages
39
Reaction score
22
Location
Lidingö, Sweden
VCDS Serial number
C?ID=205446
Thanks. I told my wife something similar this morning - 'it's failing, but it hasn't failed badly enough to be able to figure out where the problem is'.

But it has me wondering which parts would fail with this type of failure mode? It seems much more like a problem in the tank - either the pump, or a clogged screen. I have the time to remove and inspect them, so I think that's the next step. Is anyone aware of a procedure for that? I've seen a video of someone replacing the fuel pump on the driver's side tank on a gasoline Q7, but didn't see any type of screen or pickup, only a few hoses connected to the pump. Not much else out there, so I guess this doesn't fail often, and Audi was covering a bunch of these under a recall anyway.
 
   #12  

Dana

Administrator
Staff member
Ross-Tech Employee
Joined
Jan 29, 2014
Messages
4,343
Reaction score
6,369
Location
Western PA, USA
Exactly, the problem may need to get worse before the cause is entirely obvious.

In my experience Low-side (in-tank and in-line to the engine) TDI issues aren't extremely common and when they happen it is often due to metal/debris that have circulated through the system and back into the tank and electric pumps. You already inspected for metal and replaced the fuel filter so there shouldn't be metal/debris in the system. Please don't let that discourage you from checking the low-side because it wouldn't be unheard of for an issue at 158,560km/98,524miles and you don't need highly specialized tools.

Do check your repair manual to see if a volume specification is listed for the electric pump(s). I believe the pressure is roughly 5 bar based on memory. You should be able to use VCDS to activate the pump(s) using this procedure (which you likely used when replacing the filter).
 
   #13  

jmjq7tdi

Verified VCDS User
Verified
Joined
Sep 15, 2015
Messages
39
Reaction score
22
Location
Lidingö, Sweden
VCDS Serial number
C?ID=205446
Okay, now I see that the Q7 TDI has the following:
1) two in-tank fuel pumps
2) a fuel pump in the engine compartment before the filter: https://www.ecstuning.com/b-genuine-volkswagen-audi-parts/fuel-pump/1k0906089c/

So far, a failure of one of these seems to make the most sense. It seems that we would see these symptoms if any one of those is having a problem, i.e., enough fuel for low loads, but not higher loads.

Do you know if I can run all three of these independently via VCDS to do a flow/volume-based diagnostic?
 
   #14  

Dana

Administrator
Staff member
Ross-Tech Employee
Joined
Jan 29, 2014
Messages
4,343
Reaction score
6,369
Location
Western PA, USA
No, you will be limited to the single Basic Settings - 04 > Group to "035" operation with VCDS. If you want to run them independently I would firstly check the wiring diagram and then jump power and ground directly .. but make sure not to starve the under-hood pump for fuel if the ones back in the tank aren't running. I'm pretty sure that's why there aren't individual pump test provisions in the EDC.
 
   #15  

jmjq7tdi

Verified VCDS User
Verified
Joined
Sep 15, 2015
Messages
39
Reaction score
22
Location
Lidingö, Sweden
VCDS Serial number
C?ID=205446
   #16  

Dana

Administrator
Staff member
Ross-Tech Employee
Joined
Jan 29, 2014
Messages
4,343
Reaction score
6,369
Location
Western PA, USA
Either one should be fine as long as you only intend on using it for low-side testing.

You likely know this but fuel pumps shouldn't be dead headed for any extended time, and you don't want to crank or start a CR-TDI without fuel, so make sure the fittings you connect are T'd into the low side lines since I doubt you'll have an actual service port that any of those car specific fittings are going to connect to. Hopefully you can fit the one that looks like a universal T into a flexible hose that already exists on the vehicle.
 
   #17  

jmjq7tdi

Verified VCDS User
Verified
Joined
Sep 15, 2015
Messages
39
Reaction score
22
Location
Lidingö, Sweden
VCDS Serial number
C?ID=205446
Thank you, I will use the T-adaptor to keep fuel flowing through the system.

Just to consider all the possibilities, I saw that there is also a pressure relief valve on the back of one of the fuel rails. Ever hear of this failing in this way, i.e. not holding more than a certain pressure (1250 in my case)?
 
   #18  

jmjq7tdi

Verified VCDS User
Verified
Joined
Sep 15, 2015
Messages
39
Reaction score
22
Location
Lidingö, Sweden
VCDS Serial number
C?ID=205446
I don't have my fuel pressure testing tool yet, but I have been reading about the 3.0 TDI fueling system used in VW/Audi and have a very simple test in mind that wouldn't require a fuel gauge, and would like to know what you guys think. Would this tell me anything conclusive, and do you see any dangers with the steps I've proposed?

Theory: The secondary in-tank fuel pump has failed or is very weak.

Rationale: The car runs perfectly fine (manages high pressure in the rail quite well) until it reaches an RPM level requiring more fuel flow and pressure. The Audi Q7 has two lift (in-tank) fuel pumps, and both run continuously. If one of them is bad, then alternately disconnecting each pump should isolate the one that has the problem.

Of course, there are several other possible reasons that the fuel system can't generate enough pressure, but none that seem as simple and easy to test as this theory.

Test 1: Determine if the secondary pump flows any fuel at all
Step 1 - Disconnect the wiring connector (or is there a dedicated relay?) from the primary in-tank fuel pump
Step 2 - Disconnect the wiring connector from the in-line fuel pump in the engine compartment.
Now, only the secondary in-tank fuel pump is connected to power.
Step 2 - Remove the fuel line from the input side of the fuel pump in the engine compartment and route a temporary connection to a gas can.
Step 3 - Turn on the key. Activate VCDS to run the fuel pumps. If I don't see any fuel, bingo, I've found a problem with the secondary fuel pump (either the pump itself, a relay, wiring, etc.), and I need to test power to pump (and possibly work my way back). If I do get fuel, then measure the volume of fuel that was pumped and repeat this test with only the primary fuel pump connected and compare the volumes (I assume that both fuel pumps have the same specs for flow rate - if that is wrong, please let me know).
Step 4 - Put everything back together and use VCDS to prime the fuel system.

If the secondary fuel pump is only partially failing/weakening, this test might not be very conclusive. But I think it's worth a shot. Do you see any potential problems?
 
Last edited:
   #19  

jmjq7tdi

Verified VCDS User
Verified
Joined
Sep 15, 2015
Messages
39
Reaction score
22
Location
Lidingö, Sweden
VCDS Serial number
C?ID=205446
I found some interesting info from SSP 351 (which is for the Toureg/Phaeton 3.0 TDI):

When the ignition is switched on and the engine speed exceeds 40 rpm, the two electric fuel pumps are initialised
by the diesel direct injection system control unit J248 via the fuel pump relay J17, and build up pilot pressure.
As soon as the engine is running, both pumps continuously pump fuel into the fuel supply system.
The right-hand chamber's suction jet pump pumps the fuel into the pre-delivery tank for the fuel system
pressurisation pump G6, and the left-hand chamber's suction jet pump pumps fuel into the pre-delivery tank for the
fuel pump G23. Both suction jet pumps are driven by the electric fuel pumps.

Effects in the event of failure
In the event of pump failure, a lack of fuel may lead to deviations in fuel pressure in the high-pressure accumulator
(rail) in combination with a fault memory entry. The engine's output is reduced.

------------------------------------------------------------------------------------------
The good thing is that the 'Effects...' description matches exactly what's happening to me, so it seems that I'm on the right track.

I finally broke down and bought an hour of ERWIN so I could get correct documentation for my car, so hopefully I can figure out the best way to electrically isolate and test the pumps without trying to run the vehicle at all. Apparently starving the HPFP is extremely bad.
 
Last edited:
   #20  

jmjq7tdi

Verified VCDS User
Verified
Joined
Sep 15, 2015
Messages
39
Reaction score
22
Location
Lidingö, Sweden
VCDS Serial number
C?ID=205446
I gathered all the material I could find in Erwin that seemed to be applicable. One thing I could not find is a specific diagnosis checklist of all the test procedures for code P0087. Is there supposed to be such a thing in Erwin, or is this only available through Audi's maintenance computers?

In the absence of this checklist, I'm following my initial theories, so I've run the test "Checking fuel system pressurisation pump -G6-/fuel pump -G23-, vehicles with 3.0 ltr. (V6) or 4.2 ltr. (V8) engine up to 05.2010". The result was very surprising, but inconclusive.

I don't have VAG tool 1348 to independently power the rear pumps, but I thought I should be able to use VCDS to duplicate it. When running the pump using group 035, VCDS powers both rear pumps (G6 and G23) AND supplementary front fuel pump V393. I wasn't sure how this would affect the test since the VAG tool says it only powers the rear pumps, so I ran it both ways - with V393 connected and running, and with the wiring at V393 disconnected so that only both rear pumps were running. The fuel cap was off as prescribed. The engine (and all pumps) were cold, so if the problem is only affecting the car when the pumps warm up, this test wouldn't confirm that. According to the procedure, I should get a minimum of 550 cubic centimeters (mL) after 15 seconds of pumping. We used the on/off button in VCDS to limit the pump run time to 15 seconds in each test. I got exactly 1100 ml in both tests, whether V393 was connected or not. This seems to eliminate the possibility of clogged strainers in the tank (which is not surprising given how clean the fuel filter was) and a failure of either of the tank pumps.

Any comments on this test?

Since I don't have a checklist, my next guess is to run the diagnostic test for the fuel pressure regulator valve, N276, mounted to the back of the fuel rail. In some applications such as US trucks, this component has as high a rate of failure as anything else for my symptoms (it's not particularly high, but it is one of the more common culprits). I really, really hope that's the problem, because if it's not, then we're looking at the likelihood of an HPFP failure, or a failure of the flow metering valve on the pump (which doesn't have its own diagnostic procedure).
 
Top