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

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

Postby STC » Sat Nov 19, 2016 3:20 pm

I looked at this car with Richard late yesterday afternoon. He will be along shortly to share the waveforms and his views.

Having thought about this overnight my Initial observations, thoughts and facts are as follows.

1. When you turn the key to crank it will not always Crank. If it does it is always with a 3-4 second delay and it will not crank for long - A volt Drop test needs to be carried out to the starter motor Terminal 50 -- Is it being energised on the turn of the key ?
If yes then the B+ to Starter and Engine Earth should be Volt dropped with a scope


2. When it does crank it "sounds" like it is Hydro Locked on at least one cylinder, it does try to fire. An amp clamp on an Injector confirms Injector activity. That confirms RPM and FRP does it not ?

We then Scoped Starter and Injector 2 Current to establish that Cylinders 1 & 3 are drawing obscenely high current ~600amps.

Next I unplugged FRP, Rail Pressure Regulator and loosened off a HP Pipe with a view to stop fuel entering the cylinders and hoping any liquids (fuel, water, oil) in there would be forced out of the exhaust valve - No noticeable improvement.

We then pulled the injectors, but still had the few seconds of delay after turning the key and it would stop cranking after a few seconds. I'm not so sure it should do that - Am I right ? Perhaps a dickie Brake Light Switch ?
I would like to fix that first !!!

Should this be a Valve Train Issue, (spun Rockers, sprockets... etc.) let us assume that all 8 valves in Cylinders 1 & 3 never opened, would that cause such a restriction to engine rotation that it would cause the Starter to pull 600 amps ?
Perhaps we have 2 cylinders coming up on a compression stroke together ??? Doing twice the work pulling twice the amps ??? Possibly a bit far fetched but possible I guess ?

That Richard would be a good reason to drop the WPS into each cylinder, with a position reference from CKP or even CMP for easier access (the hard work is done, injectors are out)
Last edited by STC on Mon Nov 21, 2016 10:37 am, 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 grunf1976 » Sat Nov 19, 2016 3:38 pm

I agree with your Idea for voltage drop testing. As for brake switch you can see it using VCDS. There' a mvb that shows if switch is working when depressed.
As for the valves, it is plausible. This Engine has valves at 90 deg. against pistons. they dont bend when piston hits. but they smash rocker arms and lifter. so if they are closed there's your resistance.
It shouldnt stop cranking on it's own. It has a starter relay. Maybe it is cutting out?
How does the engine sound while cranking once you pulled the injectors?
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby STC » Sat Nov 19, 2016 3:54 pm

Hi Grunf

It shouldn't stop cranking on it's own. It has a starter relay. Maybe it is cutting out?


Indeed, and a multiple of tests can be carried out at that relay, Control, Supply & Load side of it can be confirmed.

How does the engine sound while cranking once you pulled the injectors?

Sounds good, just what you would expect from an engine with injectors removed. No mechanical clunks or knocks, however it will only crank for a few seconds and the starter cuts out.
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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 4:06 pm

I would look at the command circuit for starter relay. It could be losing power on account of bad igniton switch. Usually when ignition switch goes it throws a fault code. Something like ignition switch D. It is simple in design. To me it looks like potentiometer :D sorry for spelling.
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby STC » Sat Nov 19, 2016 4:15 pm

It could be losing power on account of bad igniton switch. Usually when ignition switch goes it throws a fault code.


And not an uncommon failure on the VAG cars, I'm sure I have seen a MVB for Ignition Switch Status - I'm Guessing in Steering Wheel Electrics ??
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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 4:19 pm

Yes and I think it shows up in 09 central electrics. and I forgot to mention as i saw in the beginning of this topic, these engines have no problems with glow plugs. the problematic ones are 3.0 tdi. so these plugs come out no problems.
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby FioranoCars » Sat Nov 19, 2016 6:07 pm

Hi All
Sorry it all took a bit longer to get the files organised, but here we go, a few captures to consider and pick apart, with my initial thoughts, some of which might or might not be input from STC, who may or may not agree with the statements here, as while we agreed on lots, we did have some minor differences of opinion :shock: , but without his input and help, we'd still be a big step behind, so once again thanks, but I'll take full responsibility for any daft statements (so all opinions of stupidity are mine alone :oops: ) and I will only share any praise ...

Channel A = Battery voltage at battery
Channel B = Amp Clamp 2000amps on battery cable
Channel C = Amp clamp 20amps on Injector 2 (last capture only)

Test A
First capture was fully charged battery, first crank for 24hours, while the battery is not correct for the car, it should cope fine as it's 600CCA.
cranking1 - TEST A.png
Test A

cranking1.psdata
first test - Test A
(195.74 KiB) Downloaded 5 times

The cranking shows at least 300amps to rotate, with compression peaks over 750amps on 2 cylinders, and over 400 on the other 2.

so
a. More AMPS than I would consider as correct ... but I'm no diesel expert
b. the time taken to rotate past the worst cylinder increases with cranking, could that be a build up (fluid in cylinders?)
Ok, so these thoughts are in hindsight to the further tests, but not too different to those expressed at the time...
rotations, well we are at a full 720° in 900ms so about 120-140rpm cranking
Key side notes:
- initial crank was instant, no delay. All the other tests had a delay between key to +50 and starter motor activation
- Seems to be attempting to start ... but that's hard to say for sure

Test B
Next we added a charger as the 2-3 tests already done were taking their toll
Changes: disabled the fuel pressure sensors (both) at the fuel rail.

Cranking3 - TEST B.png
Test B

cranking3.psdata
test B
(176.13 KiB) Downloaded 9 times


a. Still needs over 300amps not during compression, compression element still 2+2 split 400+amps and 600+amps, about 50% extra for 2, aprox.
b. The speed has increased to about 200rpm cranking
c. each cylinder is closer to equal time to rotate, unlike the clear difference in capture A above
d. same partern of 2 cylinders being worse then another 2

Key side notes:
- delay between key to +50 and starter motor activation
- still Seems to be attempting to start ...

Test C
This is will the addition of injector 2 amp clamp to ID cylinders. Battery pack and charger now in use to sustain testing, sorry second battery pack, killed one already! Serious Amps being drawn.
Cranking5 inj2 1342 - TEST C.png
Test C

cranking5 inj2 1342.psdata
Test C
(191.01 KiB) Downloaded 5 times


a. Rotation speed during cranking is now aprox 260-270
b. Confirmed same 2 cylinders always with the higher amps (lots of captures, not just this file)
c. Harder to keep cranking going for any length of time, stops and tries again itself, but less continuous time each attempt.
d. Still 300amps for "good" 2 to reach compression, bad two can be anything from 400-700 amps, no real pattern as to why that fluctuates so much.

High amps identified on cylinders 1 and 3, see below
audi a3 firing order.png
firing order identified from injector 2


Test D
Final capture, for now ...
Change: injectors all removed so we can see if this is down to some mechnical issue or a compression issue.

cranking6 no injectors removed - TEST D.png
Test D

cranking6 no injectors removed.psdata
Test D
(224.96 KiB) Downloaded 5 times

a. rotates after initial inrush at about 192amps, much higher than our petrol engine, which would be at that level with plugs etc intact!
b. no longer a discernable 2 vs 2 issue, all 4 cylinders appear balanced in terms of requirement
b.1. would this rule the crank out? I think so ...
b.2. would this rule cams out? ... I think not entirely, but maybe? It's hard to guess here, but, if the cams (lobes or sprocket) had rotated so that the valves where opening or closing at the same point as another cam (allowing double compression when all things sealed), then surely you'd see some indication of this in the amps, for the force needed to open the now imbalanced cam lobes?

OK, so there is 8-10 amps variation, but not sure how much work is needed to understand this verse valve timing events, and then trying to map against potential unknown valve train failure posiblilities ? Would need to get an ID from crank or cam sensor, as injector removed :-)
no injectors slight amp variation.png
zoom showing slight amps variation when no injectors during cranking


confession, so we are not entirely sure that the cylinders are free from fluid (water, oil, diesel), so this will need to be confirmed, and might be pivotal. watch this space.

Anyone have further analysis of captures they can add ... Please shout ... all files uploaded, so play to your hearts content ... I will edit channel file data to make them more suer friendly, well for any that finally go into the waveform library once we're finished...

Current leanings:
Excess compression of 2 cylinders - what can cause this?
a. smaller compression area
b. part of the compression area filled with substance with less compressible properties (ie not fuel/air gas mixture)

Excess force to rotate engine
a. valve train issue (lobes/sprocket) -
aa.double compression on 1 cycle, normal compression on other cycle of 2 stroke.
ab.other interference/damage
b. crankcase issues
c. oil starvation in key parts, affecting 2 cylinders - a stretch I know!
d. external interference - aux belt, gearbox/torque converter?

what don't we think it is:
- aux belt based loads but will slip off belt if things look this way

Possible secondary issues, once initial thinks resolved
- fuel pressure
- fuel injectors (leaking fluid ?)
- glow plugs

Next test ideas ... feel free to chime in
1. Is the near 200amps to rotate the engine good? Full volt drop test, should have already done it, but with 600+amps the volt drop would be so high as to mask any cable issues, 200amps is manageable to understand cable performance.
1a probably try to get crank cam waveform while we are there
2. if we can recode (if they are coded) move the injectors, to see if the issue follows them ...
2.a Repeat with top lambda removed, see if we can hear or see anything different
3. Do a real compression test, to see if the lower amps cylinders are good, or low, so we can chase the correct 2, post test 2, so we know that outcome first, as key to know if a simple component move changes the cylinders involved.
4. We could endoscope the inlet to see what's going on?


Otherwise, I think it's cam cover off to see the cams and inlet side of things first hand ...

Ok, will reply to other posts tomorrow

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

Postby steevegt » Sat Nov 19, 2016 6:59 pm

If the exhaust valves on cylinders number 2 and 4 never open, you end up with the same current pattern, because cylinder 4 and 2 are producing 2 compression events per 720 degrees.

You could validate this in many ways.

In cylinder cranking pressure waveform for cylinder 4 (and 2) should produce two pressure peaks per 720 degrees.

Because you already done that, you could remove injector number 4, and the current for cylinder number 1 compression should reduce to half the value. This will prove that the extra current you need for cylinder number 1 is coming from cylinder number 4.

Exhaust pulses may say something, but I guess the first 2 options should be more conclusive.

I guess that other valve "timing" issues, could create the same symptoms, but exhaust valves not opening are the simplest explanation I could find.
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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 7:23 pm

What I would do at this stage is either put wps in and measure cylinder pressure, or if your injectors are already out pull the valve cover and check to see if there is anything out of place. It would be obvious on that engine
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Re: Audi A3 2011 2.0 TDI (8P1-CFGB) Crank no start, no DTC c

Postby grunf1976 » Mon Nov 21, 2016 5:07 pm

Any update on this ?
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