VW Golf4 BCB not start

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VW Golf4 BCB not start

Postby victor2k » Sat Nov 26, 2016 6:40 pm

Hello,
I have a 2002 VW Golf4 /BCB petrol engine type/WVWZZZ1JZ2W680799 and I can't start the engine.
The engine compression is abnormal high:14,17,17,17 bar (measured with Pico and regular compressmeter).
The cylinder pressure waveform is abnormal at exhaust opening/closing valve(point 1 is ok ,point 2 is too early(aprox20*)),also the pressure in cylinder through exhaust phase is abnormal high(wear of exhaust cam lobe?).
I can't aprox the moment of intake valve opening in my capture,maybe someone can help me.
In diagnose I have only missing comunication faults(the battery isn't very good) .ABS or Airbag will not block the start of engine(I think).
Also I can't find a good reference for CAM /CRANK sync for BCB engine so any help is wellcome.
Thank you.
Attachments
161126_CompressionTest_001.pddata
(109.46 KiB) Downloaded 24 times
Volkswagen_Golf_2002_Petrol_20161126-0001.psdata
(11.13 MiB) Downloaded 35 times
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Re: VW Golf4 BCB not start

Postby PicoKev » Sat Nov 26, 2016 10:53 pm

Hi Victor,

I cannot open your files at the moment but According to my data the the 16V 1598cc BCB engine should have a compression pressure of 14 - 21 Bar (Minimum 7 Bar) and a maximum cylinder pressure differential of <3 Bar so your compression's do not seem to be excessive for that engine.

I presume you have fuel and spark?

This looks like the rear cam is driven by the main belt and then a link belt drives the front cam.

Fairly easy timing check, Zero mark on crank pulley aligned and pin in each cam sprocket if you in any way suspect a valve timing issue.

Kev.
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Re: VW Golf4 BCB not start

Postby serfer66 » Sun Nov 27, 2016 11:08 am

Clogged exhaust system? Remove the lambda probe upstream of the catalyst and try to start the engine
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Re: VW Golf4 BCB not start

Postby antreas26 » Sun Nov 27, 2016 10:51 pm

From the 2nd psdata i see a lot of backpressure 865 mb tha is 12,5 psi.That is a lot of pressure victor2k.I agree with serfer66 about taking out the upstream and trying to start if you have fuel and spark.
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Re: VW Golf4 BCB not start

Postby Steve Smith » Mon Nov 28, 2016 7:46 am

Hello and thank you for the posts and files.

Looking at the psdata file we have a number of issues, most certainly excessive exhaust back pressure on the cylinder under test.

I can also see advanced exhaust valve timing and possibly an advanced intake event too.

WPS VALVE TIMING-EXHAUST RESTRICTION.jpg
Valve timing error


Would it be possible to look at other cylinders with the WPS?

If similar waveforms are repeated across all cylinders then camshaft timing has to be suspect

If this waveform is specific to one cylinder only then perhaps camshaft to valve relationshiop has to be suspect

To reveal the intake event during cranking, restrict the air intake to create a vacuum that will help reveal the intake event. Note: Peak compression will be lower as a result.

I hope this helps, take care......Steve
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Re: VW Golf4 BCB not start

Postby victor2k » Mon Nov 28, 2016 10:23 am

Hello,
The catalyst was blocked.Removing the first lambda sensor the engine start
Here is the new capture with the engine starting.
How work enhanced capture on 16 bits?The hardware is capable to work on 16 bits or is a software improvement of signal(like a signal conditioning) ? :?
Thank you
Attachments
Volkswagen_Golf_2002_Petrol_20161129-0001.psdata
(24.57 MiB) Downloaded 11 times
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Re: VW Golf4 BCB not start

Postby Steve Smith » Tue Nov 29, 2016 11:03 am

Hello Victor, thank you for the feedback and great news.

I still have a concern surrounding the valve timing of the cylinder waveform below.

VALVE TIMING.jpg
Expansion pocket


I have highlighted the expansion pocket that rises to atmospheric pressure earlier than normal. (food for thought)

Do we know why the catalyst is blocked at this stage?

Take care.......Steve
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Re: VW Golf4 BCB not start

Postby victor2k » Tue Nov 29, 2016 5:29 pm

Hello,
The isolator of ignition coils at cyl 2 and 3 was broken.
The catalyst was melted by unburned petrol.
The timing belt was checked and was found ok.Also about the opening of the exhaust valve...the beginning of opening of the exhaust valve is ok at 145*(50*-20* before BDC) after TDC but the middle of the curve of exhaust is advanced with 20* :?: That was one question in my first post
Also we need a math for crankshaft rotation(in my files 1 and 2 the teeth with the same width ) so from 0* to 720* can't use a liniar representation,
Thank you
Attachments
2.png
1.png
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Re: VW Golf4 BCB not start

Postby victor2k » Sat Dec 10, 2016 8:30 am

Hello,
I think we need to integrate freq(crankshaft signal)*time( between 0* reference and the place of marker) to show a accurate measurement but I don't know how to implement this. :?
Also we must ignore the false frequency fall caused by reference(at 180* or 360* ) in this formula(based on the speed of frequency dropping limit ).
My madness started from a similar event to the following images(captures was made with the same setup on Ford Puma 2002 /petrol/1.6l):30* diference on a non-vvt engine between first and second measurement(vvt or non-vvt does not matter at cranking and idle anyway)! :evil:
Thank you.
Attachments
2.png
engine at idle
1.png
engine cranking
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Re: VW Golf4 BCB not start

Postby steevegt » Sat Dec 10, 2016 7:50 pm

I believe you are right victor.
I found myself in the past counting for crank pulses after TDC mark, to be more sure about timing events and angle, not trusting the rulers.
The picoscope software rulers are a good tool, but we need to remember that the angle shown has the assumption that the engine is rotating at constant speed, so that the angle could be guessed as a linear relation to time.

In an engine with one or more disabled cylinders, and all type of problems we may find, we could have a very unstable speed in the engine during the 720º.

If the software could use the crank sensor, as you said, especially with high resolution ones (60 tooth or more), we could have a better angle guessing than just using time relation.
Small feature request!? :oops:
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