Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC codes

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Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC codes

Postby FioranoCars » Fri Nov 18, 2016 11:17 am

Hi Grunf
Already in some need of Audi help !!

We've had one of out staff get back from the police his Audi A3 2011 2.0 TDI (8P1 - CFGB), some rotters pinched it and crashed it (front end light damage, back from bodyshop already), his pride and joy.

Sadly the car is now a non-start, cranks (maybe a bit slow, and delay from turning key to crank of about 2-3seconds) and continues to crank after key released, but not firing at all. No error codes in Bosch EDC17, ABS has a tyre pressure check error (01325) and power steering (03803 - can't reset until we can start the car), otherwise nothing powertrain related showing. Bodyshop managed to kill the battery, so was on a temp one during these initial tests.

Also noticed the parasitic drain after about 5minutes sits close to 8-15ma but jumps to 80-110ma every minute or two, and regularly touches 40-60ma. Did not leave for a full 45mins, so may well settle. Is this normal? And finally on connection of a battery, the car demands 65-100amps for a few seconds. basically too much for a PowerProbe hook! (copes with 100amps inrush), this is not normal for cars we usual work on. Is that a clue?

We could not find any data on inertial switches, but ECU has a parameter for something you might interpret as a fuel cut off, with a value of 255. Both LP and HP pumps make "pumping" noises when activated via the diagnostics, of course might not be pumping and if inertia is a valve, then not going anywhere!

We have both VCDS and VAS5054, if that makes life easier to explain/request specific data values?

Does this car have an inertia switch? If so where and can we reset/bypass it to test?
We will try and get someone back on it tomorrow to do starter motor and cable tests, and then maybe power the starter directly to get crank/cam signals on the scope as we're there ...

Any common issues we should be looking for? Otherwise we're back to the Fuel, Air, Compression generic requirements of a diesel engine ... an area we don't do much work! It's not our usual car type!

"What the DPF is that?" comes to mind :twisted:

Anyone want to pitch in? TIA ...

Richard Lukins
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Ferrari Maserati Lamborghini and Porsche Independent Specialists
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby steevegt » Fri Nov 18, 2016 12:17 pm

Maybe I will start to scope crank, cam, rail pressure and injector current.

If the ECU does fire the injectors, that does mean that most likely you don't have an input problem, like a inertia switch (physical or software type of switch).

Keep in mind that if you don't have enough pressure, the ECU will not fire the injectors...
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby STC » Fri Nov 18, 2016 12:46 pm

Richard.

the car is now a non-start, cranks (maybe a bit slow,


Until such time that minimum RPM and Fuel pressure thresholds have been achieved the ECU will not fire the Injectors.

It is an emissions and catalyst protection thing, No point put the fuel in if there is little chance of it igniting.

as Steeve said
start to scope crank, cam, rail pressure and injector current.


Wont hurt to do a relative compression test first.
Does this car have an inertia switch?

Pull the supply pipe off the filter, that will tell you if the in tank pump is running. It will run for a few seconds at Ignition on to prime it but should run continuously whilst cranking.
Last edited by STC on Fri Nov 18, 2016 1:04 pm, edited 1 time in total.
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby FioranoCars » Fri Nov 18, 2016 12:59 pm

Thanks Steeve & STC
BUT ... can you be more specific ... please ...

What sort of fuel pressure for this car, not looked, but assume we can measure at the rail (if not suggestions where to measure - from a practical point of view as well as diagnostically relevant)?

Where is the car's fuel pressure sender (correct, have no tech data for this thing!), so we can monitor output at sensor (OK, can check live data on tool too ... but nice to know where it is, just in case)

What's the likely min threshold for cranking rotation needed? 200rpm, 300rpm? Is there any manufacturer data in case this is critical?

On these smoke boxes what's the aprox compression pressure we should be happy with ... yes diesel numptie here :oops:
Yes I will get a relative done first, but as we have a WPS we may as well rule it in out conclusively by doing the real deal, don't want to have to back track, test once thoroughly and avoid doubling back !!

Thanks
Richard
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby steevegt » Fri Nov 18, 2016 2:39 pm

FioranoCars wrote:...
What sort of fuel pressure for this car, not looked, but assume we can measure at the rail (if not suggestions where to measure - from a practical point of view as well as diagnostically relevant)?

Where is the car's fuel pressure sender (correct, have no tech data for this thing!), so we can monitor output at sensor (OK, can check live data on tool too ... but nice to know where it is, just in case)
...


You measure at the rail, usually using the rail pressure sensor. You can T a gauge in there, but it has to be a dedicated type of tool, because we can reach in excess of 2500 Bar of pressure.
The sensor is located at the end of the rail.
It produces an analog type signal (usually 0.5 volt plausible signal at 0 bar).

I don't have tech info for crank pressure values, but more than 250 bar for sure. Maybe more than 300 ou 320 bar cranking, as this is a modern common rail. (please fix my numbers if there are not correct for this system)
You can just use scan data to get the pressure values, usually it is ok to discard a no fuel pressure problem.

FioranoCars wrote:...
What's the likely min threshold for cranking rotation needed? 200rpm, 300rpm? Is there any manufacturer data in case this is critical?
...


I would say 200 to 300 to be ok...

You can validate both of the above, RPM and rail pressure (at least seen by the computer), if you have the injectors commanded.

FioranoCars wrote:...
On these smoke boxes what's the aprox compression pressure we should be happy with ... yes diesel numptie here :oops:
Yes I will get a relative done first, but as we have a WPS we may as well rule it in out conclusively by doing the real deal, don't want to have to back track, test once thoroughly and avoid doubling back !!


I have this message in the compression values for this engine:
Carry out compression test using diagnostic equipment (do not remove ceramic glow plugs).


This means that you should have a way of measuring compression using just the scan tool. I don't know if we shouldn't measure compression directly!? (risk of damaging the glow plug??)
Maybe someone may explain better the "do not remove ceramic glow plugs" sentence.

I'm not familiar with this test, but I guess it may be a relative compression test (using crank speed!?, system voltage, or current). But I can't be sure if it isn't an absolute compression test using the glow plugs pressure sensor, if this system has that type of sensor fit inside each glow plugs.
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby STC » Fri Nov 18, 2016 8:34 pm

Maybe someone may explain better the "do not remove ceramic glow plugs" sentence.


Remove them if you wish, not an issue. Just have a some engineering tools (Drill bits, a Steady Hand, Thread Cutting Taps etc.) and a replacement set to hand. After all they are a serviceable item. Less risky to remove them from a hot engine but with this as a non start. Richard does not have that luxury. That goes as much for Ceramic & Non Ceramic Variants

But I can't be sure if it isn't an absolute compression test using the glow plugs pressure sensor, if this system has that type of sensor fitted inside each glow plugs.


Pressure sensing Glow Plugs are becoming more and more common but the VAG CAGB - 2011 MY does not have them. Just conventional ones.

but as we have a WPS we may as well rule it in out conclusively by doing the real deal, don't want to have to back track, test once thoroughly and avoid doubling back !!


Richard, I'm thinking your obstacle here will be a Diesel Compression Test Kit to attach to the WPS - Shout and I will lend you mine.
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby FioranoCars » Fri Nov 18, 2016 11:39 pm

Hey, I really appreciate all the comments, thanks.

Ran some tests, which I'll post tomorrow, and thanks to STC for popping over .... And giving valuable devils advocate input, and for the familiarity with the engine, otherwise we'd still be finding the fuel rail !!!!

Seriously, a bit thanks STC

Ok, the waveforms will follow, but we have two cylinders needing almost double the amps to crank, and two at roughly normal levels, being circa mid 200's verse 350 to 600 amps for the 2 "bad" cylinders.

Id'd the bad ones from injector signal, so they are attempting to fire. Fuel rail pressure sensor, both, removed same result of two high amps, and cylinders not sloshing in diesel.

With injectors out, there is inrush current, but not discernible difference between the four cylinders, IE almost dead flat current signal once rotating, so issue is down to cylinder compression being excessive verse crank or cam, not might initial thought of valve tappets being over pressured ... Or so I'd read into the flat current to rotate ...

Battery is killed within 4-5 sets of 10second bursts of cranking, even with full charge and battery pack with number of cycles is limited, so some serious mechanical issue here.

No WPS done, as I don't think the actual pressures will add much to the resolution/diagnostic, might be nice but no real value at this stage ... Unless you can tell me why ...

I'm thinking strip the cam cover inspect valve train, and if nothing there, inspect exhaust manifold/ turbo but don't think our two cylinders share much in the exhaust dept...

Weird circumstances of the car mean Pandora box of what we might find, but seriously would love to hear thoughts on further tests we can do or indeed ideas or insight into what we might find.... Yes there is oil in the sump, and fuel in the rail... Still no DTC ... Sorry did not get to crank cam signal as sensors hard to reach and don't think part of our core issue...

Waveforms tomorrow

Best
Richard
Ps, thanks again STC, above the call, and put up with my Friday afternoon bad manners, at least you got warm coffee :D
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby grunf1976 » Sat Nov 19, 2016 1:32 pm

Hi ,
sorry for late reply had to deal with Passat from hell! Firs i would take a look at the compression. those cars have a flaw with the camshafts. Recently I had one that turned the sprocket on the intake cam. Compression shuld be minimum 22 bar. That is the wear limit.It goes for all VW diesel's. second thing is that it wont start until it get's to 300 rpm. Only then it inject's the fuel. idle pressure should be around 250-300 bar. How many km's on the clock? check the metering valve on the pump for aluminum shavings.And one last thing that comes to mind.Check if the flap on the intake manifold hasn't stuck in the closed position. That can happen because of the gunk that EGR produces.Hope that this helps. If I can help furhter Im here!
Last edited by grunf1976 on Sat Nov 19, 2016 1:53 pm, edited 1 time in total.
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby Liteace » Sat Nov 19, 2016 1:34 pm

Have these got cam lobes pressed onto the camshaft ? maybe they spun
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby grunf1976 » Sat Nov 19, 2016 1:54 pm

not the cam lobes but the sporckets are. And when they move rocker arms are the ones that go, since this is interference engine. but the god thing is it doesent damage the valves. they are set at 90 degrees.
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