'14 Golf 2.0L TDI CJA Crank No Starty

Got my ass handed to me Friday afternoon by this TDI. Towed in, crank no start. Intermittently, it huffs and puffs like it wants to start. A couple times, it started briefly before dying despite throttle input. 90% of the time, it's just a good ol' no starter.

I've added the VCDS code scan, but here are the highlights:

Address 01: Engine (CJA) Labels: 03L-906-022-CBE.clb
Part No SW: 03L 997 030 D HW: 03L 907 309 AA
Component: R4 2.0l TDI G000SG 9983
Revision: 12H16--- Serial number:
Coding: 0050072
Shop #: WSC 09060 003 1048576
VCID: 2F2E00CEBEB1EEF766-807A
VINID: 9E69DE74745A1959C000000310D6C350B3

2 Faults Found:
011174 - NOx Emissions Exceeded
P2BA6 - 000 - SCR Catalyst Malfunction - MIL ON
Freeze Frame:
Fault Status: 11100000
Fault Priority: 2
Fault Frequency: 1
Reset counter: 255
Mileage: 180749 km
Time Indication: 0
Date: 2016.10.28
Time: 22:23:18

Freeze Frame:
RPM: 0 /min
Speed: 0.0 km/h
Load: 0.0 %
Pressure: 955.9 mbar
Temperature: 24.3°C
Mass Air / Rev.: 1100.0 mg/str
Temperature: 40.5°C

006744 - NOx Catalyst
P1A58 - 000 - Regeneration Required
Freeze Frame:
Fault Status: 01100000
Fault Priority: 6
Fault Frequency: 4
Reset counter: 255
Mileage: 180749 km
Time Indication: 0
Date: 2016.10.28
Time: 22:23:18

Freeze Frame:
RPM: 0 /min
Speed: 0.0 km/h
Load: 0.0 %
Pressure: 955.9 mbar
Temperature: 24.3°C
Mass Air / Rev.: 1100.0 mg/str
Temperature: 40.5°C

Readiness: 1 1 0 1 1

I'm told that the SCR codes are old news and have been ignored for awhile. :lol: Anyway, since I've seen high pressure fuel pump failures on these previously, my first check was rail pressure. It was disappointingly good:



Rail pressure may be a bit erratic, but it's there. 207 RPM cranking speed isn't spectacular, I know, but the battery was dead when I got to it.

I move on to possible mechanical/breathing issues. I take a cam crank waveform with a current probe on the #1 injector:





This appears good compared to the (only) known good I could dig up:

diag.net/msg/m1qyflnr89ke721kzzflmoqgoo



Swing and a miss. SCR codes stored - Maybe it's got a massive exhaust restriction? So I pull the upstream NOX sensor. No improvement.

Thinking maybe there's an intake restriction, I watch the boost and MAF sensors during a crank:



A slight vacuum on the boost sensor, and some activity on the MAF. It's trying, I guess? I don't normally watch these PIDs on diesels during a crank. :silly:

Desperate, I pull the intake tubing off. Still no improvement. But I do notice what seems like an excessive amount of diesel fumes coming OUT of the intake during cranking. :huh:

What am I missing? As usual, any thoughts, ideas or WAGs are welcome!

If throttle body won t open for any reason is not possible to start engine?!

derekoliveira wrote:

If throttle body won t open for any reason is not possible to start engine?!

You mean the J338 Throttle Valve Control Module?



I suppose so? :huh: Usually that throttle valve defaults to 100% open until EGR flow is commanded... I'll have a look at the indicated scan tool position on Monday.

Forgot to mention in the opening post that I did take a fuel sample and found clean diesel.

Updating this one with what I found today. It appears we're dealing with an intake restriction? More on that in a moment.

The gentleman and scholar known as Juergen suggested using a piezo sensor on the injector rail to confirm that the injectors are actually opening. Solid idea. I combined that with a relative compression just because. Putting the sensor on the rail itself didn't get me much. :huh: But putting it on the individual injector lines produced some really nice waveforms!

Relative compression in green, #1 injector current in red, piezo sensor on the #1 line in blue:



Same for the #4 line:



The #2 and #3 look similar. I was pleasantly surprised at the amount of detail that can be seen in the injector operation with the injector current and the piezo sensor:



Cool waveforms aside, this was ultimately a dead end. :silly: Rail pressure is there, injectors are opening.

Taking derekoliveira's suggestion, I did check the G338 Throttle Body Control Module. During Output Control and Basic Settings, the throttle does open and close as designed. Still a good suggestion.

What else are we missing? Another technician suggested pulling the boost hose off at the throttle body, just for giggles. I explained why I didn't suspect an intake restriction (the boost sensor during a crank), but what do we have to lose? It starts. :lol:

So where is the intake restriction? It might have something to do with this:



That compressor wheel is locked solid. I also found this in one of the boost hoses:



Oh no. Bad news bears for this one. So did my earlier cranking test with the boost sensor PID miss the problem? Maybe. The difference between engine off (13.86 PSI) and cranking (13.69 PSI) was marginal, and thus I didn't worry about it. Maybe there should be no difference during cranking?

Anyway, I'll update this one if we end up fixing it.

Thank you for the update Tyler!

This is an excellent example for showing the value of following a "game play", your persistence payed off.

The turbine wheel looks like it came off the shaft at some point and then got stuck because of a binding bearing??

There are these shiny marks on the blades.... apparently all in the same spot on each blade where they were scrubbing against a foreign oject/the housing.

Anyhow, this MUST have caused really heavy noise on its way out I'd believe.:blink:


p.s.

I see you using that Autel scope solo much