VWT6 CXEB NON START After rebuild (2017)

[cottya]

I am currently experiencing a non start issue on my CXEB engine.

It blew one of the turbos in February, I pulled the engine and stripped it completely. I had the turbo re built and had the cylinders relined at the same time. With the re build I replaced all the necessary seals/gaskets lapped in the valves etc.
It's now all back together, but won't fire up. It is really close but doesn't seem to catch and run.
There are no fault codes!

What I have done so far:
Quadruple checked the timing and and the crank timing ring.( yep I took the engine back out just to be sure when it would t fire up). Used VCDS to have a look at some of the measuring values but I am not very good with it so stabbing in the dark really.
Any direction or guidance would be really appreciated.

 

[Blasam]

Have you used the search function on here mate? I can’t help myself but I do vaguely remember reading various threads of CXEBs not starting after being stripped. They seem to point the direct of fuel pressure. Sorry I can’t help more

 

[cottya]

Thanks. I have searched but need my hand holding when it comes to vcds.

I have fuel pressure readings just don't know what's good or bad.

 

[n10n]

Check out the below post for @mmi instructions of basic parameters to log with VCDS for non-start issues - follow them and remember to tick ’Group UDS requests by 7’ before starting logging. Then post the log here.

On a same thread couple of posts down there’s also some analysis and examples of how the values look like.

Won’t start. No fault codes

Quote from WSM. (Download above) Lock high-pressurepump hub with diesel injection pumplock‐ ing pin- T10492- . Todo this,insert lockingpin intofork -2-on hub and into hole -1- behind it in bracket for ancillaries. – Pull out locking pin, and slightly loosen nut for high-pressure pulley. Before...

www.t6forum.com

 

[cottya]

I've got that screen shot but the vcds I have won't let me group the uds requests annoyingly.
Think its time to upgrade

 

[n10n]

I've got that screen shot but the vcds I have won't let me group the uds requests annoyingly.
Think its time to upgrade

Well, the option just makes VCDS to log samples faster, during cranking things change quickly so a high sample rate would be good to see things better. The log is still useful even without the setting, just not as accurate.

 

[cottya]

Got you. Thanks. I'll see if I can get a log then post it up

 

[cottya]

Here's a log of the previously suggested values to check.

 

[n10n]

Here's a log of the previously suggested values to check.

Looks all good in the log - as you say it's really close to starting, and seems to burn some fuel as rpm goes above cranking speed and air mass starts to increase. Fuel pressure looks ok as well.

Maybe there's just air in the fuel system still? There has been cases where it has taken really lot of cranking to get the injectors to do their thing after being taken out. Some people have been even driving around with engine running on one or two cylinders and then eventually all cylinders have fired up.

 

[cottya]

Thanks for the reply i have cranked it a fair bit think it was that. Infact it killed my old starter motor.
I measured the pre injection on 1 2 and 3
But only got figures for 2 and 3
1 measured 0
I'm not sure if that's normal because there isn't a pre injection 4 so perhaps doesnt relate to each injector

 

[n10n]

I'm not sure if that's normal because there isn't a pre injection 4 so perhaps doesnt relate to each injector

That's normal. There's multiple small injections on each combustion and the numbers refer to these phases. Not all of pre/post injections are even used in T6 but will still be visible in the ECU software and VCDS.

 

[cottya]

I'll slave the battery from another vehicle tomorrow and give it another good cranking session

 

[DXX]

Crack the seal on the injector pipes and bleed conventionally while cranking.
Diesel engines may have become slightly more complex but the basic principles and solutions remain the same.

 

[cottya]

I would love to do that but they are located under the charge air cooler

 

[Dellmassive]

@mmi have you looked over the logs?

Any additional input?

....

TBF it's normally mechanical timing that seems to be the cause with these things, ie timing belt change then timing is ever so slightly out, or even 180deg out.

Any chance you can get pics of the timing marks?

And maybe post a link to a video clip of it cranking and start attempting?

You will need a battery maintainer and maybe a second battery connected for any extended cranking.

Be careful not to run too long or you will cook the starter.


On vcds have we got the in cylinder compression figures to compare to a known good?

 

[DXX]

I would love to do that but they are located under the charge air cooler

Then IMO it needs to come off and be bled properly.
Another problem I’ve seen multiple times after re-build is people putting grease on the injectors to hold the seals in place. When torqued down the grease creates a hydraulic lock and the injector clamp seems to be tight.
When the engine is cranked the grease is blown out and there is now insufficient pressure / temperature for compression ignition.

 

[cottya]

@mmi have you looked over the logs?

Any additional input?

....

TBF it's normally mechanical timing that seems to be the cause with these things, ie timing belt change then timing is ever so slightly out, or even 180deg out.

Any chance you can get pics of the timing marks?

And maybe post a link to a video clip of it cranking and start attempting?

You will need a battery maintainer and maybe a second battery connected for any extended cranking.

Be careful not to run too long or you will cook the starter.


On vcds have we got the in cylinder compression figures to compare to a known good?

Thank you for sharing your thoughts. I agree with all of it. I am 100% confident the mechanical timing is correct.

I'll try and get the figures for compression. Although the bores have been relined back to original spec and brand new piston rings as part of the rebuild.

 

[cottya]

Then IMO it needs to come off and be bled properly.
Another problem I’ve seen multiple times after re-build is people putting grease on the injectors to hold the seals in place. When torqued down the grease creates a hydraulic lock and the injector clamp seems to be tight.
When the engine is cranked the grease is blown out and there is now insufficient pressure / temperature for compression ignition.

The bleeding might be my next course of action.
l rebuilt the engine so know it's not the grease issue.
New seals fitted then replaced back with the correct cylinder

 

[Dellmassive]

what happens when you try to "starter fluid" (easy start)? - will it fire?

down the airbox intake behind the air filter.

just to see if its fuel related or not?

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If it fires up with easy start then you could assume timing & compression was ok and you are looking at a fuel supply problem,?

going on the principle of Fuel+Air+Compression = power(Ignition)

so if the timing was out you will loose compression as the valves will be out of sync and it wont fire.


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https://amzn.to/3Uh8Quy

 

[cottya]

Yeah it runs with spray.

Well chuffs away for a few seconds then stops