cold start Audi A3 2.0 TDI DSG BKD

[vagman1979]

Hi,
I'm looking for some guidance/direction on an issue I have with a 2006 Audi A3 2.0 TDI DSG BKD.

if the car is left for more than 3/4 hours, it's very difficult to start - it eventually starts. I've added a non-return fuel valve to try and prevent fuel running back but this hasn't helped at all.

The temp and fuel sensor both read 18.9 C when reading the values first thing in the morning -
I have 2010 Audi A3 2.0 TDI (manual) which showed the temp and fuel sensor at 15 C, these values were read within 5 minutes of each on other on both cars.

I've captured the readings of the engine speed and camshaft speed readings when I started the car first thing this morning
you can see engine speed and camshaft speed reaching good values around 8 seconds

shall I ignore the 3 degree difference in temp and fuel readings compared to the second Audi?

does this point to a faulty/knackered starter motor which isn't providing enough power? but why does it not behave like this when the engine has been running?

I've done a full scan with VCDS and there are no faults logged.

Edited by vagman1979 on Tuesday 14th September 10:58

[littleredrooster]

Looking at those numbers (and more of that in a moment), it would seem that it takes a long time to get up to full cranking speed. My first suspicion would be the battery; try putting it on charge overnight so it is fully charged just before you turn the key.

The numbers - other than the crank speed - are a bit of a mystery (ignore the temps., I cannot see the relevance of this unless it's -15deg) because the camshaft is geared to the crank at a 1:2 ratio, so one column should always be double t'other and only the final figure gives this.

[vagman1979]

Thanks rooster, I'll fully charge the battery and measure the value on the battery before starting.

[vagman1979]

I've checked the battery and it's got a ford battery in there! spec 590a 60Ah - battery was reading 12.28 volts
I've replaced it with a Varta 800a 80Ah which measured 12.60 volts

same issue though, although I didn't log the data via VCDS, it still struggled to start for about 7-8 seconds.

just as a note, this has always been the case, when it cranks, it feels very lumpy - this was one reason I added a non-return valve on the fuel line to the tandem pump to rule out fuel going back.

I will capture another log with the higher spec battery and report back.

[vagman1979]

captured readings with new battery, still the same as before.

I'm tempted to remove the starter and check that but not sure how to test it.

[littleredrooster]

Static battery voltage only tells a very small part of what's going on. Try to measure the voltage across the battery whilst it is cranking - it may give a better indication.

It would also be interesting to know the voltage at the starter when cranking just to make sure it's getting there without a big resistance somewhere.

[vagman1979]

Thanks for the input rooster,

interesting you should mention voltage during cranking, although I didn't capture this in the logs, there is an option to measure the voltage being supplied (not sure if this is relevant), and monitoring that whilst cranking it to start showed it dropping to 7v for a second or two.

I will do another iteration, this time capturing the voltage supplied values.

[vagman1979]

took another reading, this time showing the 12v supplied values, it falls to 10.79 at its lowest point.

not sure what else I can think of now.

[vagman1979]

I've done a full scan and I get the following message there:

Address 08: Auto HVAC Labels: 8P0-820-043.lbl
Part No SW: 8P0 820 043 M HW: 8P0 820 043 M
Component: KlimavollautomatH18 0260
Revision: 314473 Serial number: 8P0820043M
Shop #: WSC 06314 000 00000
VCID: 366560074124AB39AB-8062

1 Fault Found:
00532 - Supply Voltage B+
002 - Lower Limit Exceeded - Intermittent
Freeze Frame:
Fault Status: 00100010
Fault Priority: 1
Fault Frequency: 3
Reset counter: 219
Mileage: 174243 km
Time Indication: 0
Date: 2021.08.26
Time: 15:08:09

Freeze Frame:
Voltage: 7.50 V

[vagman1979]

Ignore the above, it's dated from the 26 Aug 2021 - I killed the battery that day.

[vagman1979]

Okay, I tried using group 35 where it primes the fuel lines for about 30 seconds and initiated the process 4 times, you could hear the in tank fuel pump running, started the car and same issue, took about 6/7 seconds to start with similar values in the engine and camshaft speed.

I have noticed that there seems to be smell of diesel in the exhaust smoke, this becomes more apparent when holding the revs at 2000rpm, could this be the injector seals? loosing compression when stood for a long time?

[anonymous-user]

I had this on mine ten years ago. I replaced the starter. It helped. Then the alternator from a donor vehicle but no difference so swapped it back. Then the crank speed sensor and it helped a bit more. I managed to get down from a 7 second start to 3 seconds. It wasn’t the best but a marked improvement. Then sold the car on.

[vagman1979]

Thank you for your input SuperGP.
the alternator seems to work well, the volt readings are over 14.4v when the car is running.
the battery is also good, it doesn't feel like it looses much power when cranking (always reads between 12.4 - 12.6 in the mornings)

I have access to a running donor car, might swap the starters to see if there's any difference - see if my symptom transfers over to the other car.

I've removed the injectors, 2 were really pushed down, no movement in them at all, however the other 2 had play in them and felt they weren't seated down properly, the seals looked okay but I have ordered new ones and will be replacing them on the weekend.

[vagman1979]

If anyone else is going through a similar issue then following might help, it resolved my issue. Purchased 4 x injector seal kit and injector bolts from Darkside Performance.

everything looked okay after removing the rocking cover, I tried moving the injectors and the first 2 injectors were loose and you could move them side to side by a couple of mm, it seemed like someone had a play with them before. The bolts seemed they had been re-used and were not torqued to the correct setting on the first 2 injectors, the last 2 injectors were fitted correctly, there was no play whilst they were seated and the bolts were tightened correctly.

I replaced the 3 o rings and the nipple on each injector, used new bolts and torqued them down correctly

The car now starts up and drives much better, there is no blue smoke on start up and it fires up in 1-2 seconds.

[Smint]

Not familiar with these engines, are the injector seats inside the crankcase or external, i ask because if there's any evidence of blow by (carboned up oil residue around the offending injector) for those fitted inside then it's good practice to check the oil pick up strainer for similar carbon build up.

Hopefully the pick up is visible either by eye or use of an endoscope without having to remove the sump, its not a bad idea to do this anyway if previous neglect re oil changes is suspected or someone has been following long life oil service schedules.

Lots of engines ruined through oil starvation due to this issue.

[vagman1979]

Yes, the injector seats are under the rocker cover.

there wasn't any carbon build up, the injectors actually looked fairly new/clean so might have been replaced before.

[Smint]

Good news, thanks for coming back.

[vagman1979]

No problem, hopefully it helps someone else.

I do have another question, in the screenshot one of the temperature reading is 44.1 degrees, there seems to be two on the BKD engine, one on the righthand side of the block and another on the thermostat housing.

The reading was taken after whilst the car was stationary for about 40 minutes to allow for air out of the coolant tank.