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Discussion Starter #1
Morning all,

As some of you are aware, I've recently changed the fuel pump timing belt. The van now starts up, albeit after a fair bit of cranking. It sounds OK once it starts, and will happily idle up to temp, but it's pretty fumey and if you try to drive it a pile of smoke billows out the back. So, I registered my copy of VCDS-Lite to do some timing checks...

Trouble is, when I put the ECU into basic mode (to run TDI Timing), the engine instantly cuts out. I read another forum where the theory was that putting the ECU into basic mode stops it from compensating for bad timing, so if it is far out the engine won't be able to run. Seems to make sense?

So, questions!

1. Is there an easy way I can tell whether it's retarded or advanced, so at least I know which way to turn the thing to get it to a point where the engine will run with the ECU in basic mode! Are there any clues in the VCDS measuring blocks?

2. I keep getting an intermittent coolant temperature sensor fault (open / short to +). The dash indicator is right, and Measuring block #7 looks right (87.3 at temp). Measuring blocks 1 and 2 read about 19 degrees though!! :) Could this be causing my troubles? I believe I'd just need to change the green one that sends temp data to the ECU?

Any thoughts very gratefully received!! T:
 

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Follow this guide http://www.vwt4forum.co.uk/showthread.php?t=250147 and look at measured block 4.

1 Engine speed
2 Commencement of injection (requested)
3 Commencement of injection (actual)
4 Commencement of injection valve duty cycle

The ECU can only advance the injection timing, so if the engine stalls when you go in to basic mode, that would suggest to me that the timing is too retarded.

With the engine running normally (ie not in basic mode), compare the values you see in columns 2 and 3 and hopefully this will tell you for definite. With a well timed engine, these numbers should be very close. But as your timing is so far out, there should be a discrepancy between the two.
 

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Discussion Starter #4
Hi there, thanks again for your reply.

I've taken a screen grab of measuring block 04 with the engine up to temp:

https://www.flickr.com/photos/ioboy/14012166637/

Hopefully that will work! :)

The second column is solid as you would expect, but the third column is jumping all over the place between ~1.1 and ~3. When I captured it it was at 1.3.

Something else I read said that if the duty cycle was above 10% it was retarded. Would you concur?

This weekend is the weekend it gets sorted! Definitely! ;)
 

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Woah, duty cycle of 90%
Afaik the duty cycle is just an indication of how much work the ECU is doing to try to correct the timing. To be honest I'm not happy with that explanation as when I set mine up the duty cycle started around 60. After I got the timing near bang on the duty cycle was... around 60! So maybe someone else can give a better explanation.
 

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The duty cycle is the amount the ECU is having to advance the timing to try and get the requested/actual values to match. It doesn't go from 0-100% though weirdly. If I rememeber correctly, it goes from 14.7-90 something.

So in your case ioboy, the ECU has pretty much maxed out what it can ask the fuel pump to do, but its still not enough to get the timing it wants. ECU is requesting 2°BTDC and achieving 1.3°BTDC, so your timing is retarded.
 

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Discussion Starter #7
Evening all. Thanks for those explanations. Getting clearer I think!

Based on your advice I advanced the timing and eventually got to a stage where the VCDS Basic settings section would run. Using some other thread info I used a combination of box #2 in group 0, and the TDI timing graph to get the figure as close to 55 as possible. And it's pretty bang on now! T: Though I didn't know which engine to select as AJT is not on the list on VCDS lite. It drives prettty good now!

The duty cycle is still up around 70% though, on Measuring block 4 final box. Does that sound OK?

Cheers all for this advice. Awesome team! A:
 

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Discussion Starter #9
Hi Zmok, no sorry I'm checking duty cycle using Measuring block 04... Sorry for the confusion!
 

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OK. Lol

If its at 55 in basic settings with a hot engine then it is perfect.

Regardless of the duty.
 
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