2.5 TDI hot starting problems, oil temperature?

Posted: Wed Aug 17, 2005 2:01 pm

Hi, I’m trying to solve a problem with my father’s ’98 A4 2.5TDI quattro. It’s always been a little reluctant to start when it’s warm, taking about 15secs of constantly churning the starter motor before actually firing, it will always start instantly from cold. He’s taken it to several different Audi garages but nobody has been able to solve the problem. I’ve looked at it using VAG-COM, the water temperature sender seems to be working perfectly, we changed it for a new one before investing in VAG-COM but it made absolutely no difference. When the engine is warm I can fool the engine into starting instantly by plugging in the cool ‘spare’ temperature sender. If I monitor the quantity of fuel injected while the starter is operating, I’ve noticed that nothing is injected until the instant before the engine actually fires. The injection timing is just within limits. Has anybody got any suggestions? The car is superb in so many ways, but embarrasses itself when trying to start at filling stations!!

Just as a matter of interest how hot does your oil temperature get? The A4 doesn’t get above 80 C and an Audi technician was surprised it was reading so low after doing 15 miles of motorway driving.

Posted: Thu Aug 18, 2005 4:25 pm

no codes at all on vagcom?

oil temp sounds ok, does it rise if you thrash it? (as if you would ever do that to a quattro) take it water temp stuck on 90?

Posted: Fri Aug 19, 2005 10:15 am

Hi,

Thanks for the reply; I went over to plug the laptop back into the car last night. The hot starting problem is definitely getting worse.

It looks as though the injection timing has now drifted out of the factory limits and there are now 2 fault codes stored in the ECU:

01268 - Quantity Adjuster (N146)
37-00 - Faulty
00550 - Start of Injection Regulation
08-10 - Control Limit Surpassed - Intermittent

I’m going to download the factory injection manual from https://erwin.audi.com/erWinAudi/ and see what it says. I have a feeling of dread that the quantity adjuster is an integral part of the fuel pump as I can’t see it listed separately on ETKA.

A friend has the locking pins for the V6 TDI so I might have a go at adjusting the injection timing back to within the factory limits and see what difference it makes. I can’t imagine there is that much wrong with it because other than the starting problem the car runs beautifully.

Oh and once warm the water temperature doesn’t go above 90 and the oil doesn’t really get above 80 no matter how hard it is driven. I think that’s a little odd as they share a heat exchanger don’t they?

Posted: Fri Aug 19, 2005 1:18 pm

sounds like you got a good plan. have never been able to get much joy from erwin with vagcom/diagnostics etc, i have a bentley (doesn't cover diesels!)

i know sod all about diesels

wouldn't worry about water temp, the guage is apparently set up to read 90 when actual temp is between eg 85-95. oil temp is probably ok for diesel, i think they run a bit cooler than petrol turbos.

i think quite a few of the v6's have an oil/water heat exchanger

Posted: Mon Aug 22, 2005 7:50 pm

you mention that the timing as just within spec..
I am guessing it is late! tdi's really like to be timed
earlier than average. this will improve power, starting,
and fuel consumption...

as for the quantity ajuster... is there a powerbox installed?
these change the signals between ecu and pump to
inject more fuel... these can throw the code.

otherwise I would say that the ECU is trying to advance
the timing but because it is so late it can not advance it
enough for the warm engine....

JW

Posted: Mon Aug 22, 2005 9:04 pm

Hi, thanks for your interesting response.

There is no powerbox fitted to the car.

If I monitor the engine with VAG-COM, display group 4 and switch to Basic Setting the timing adjuster moves alternately from advanced to retarded at 10sec intervals. When the adjuster is moved to advanced (injection start valve N108 closed), the fuel is injected at 14.2deg BTDC (specified limits are 14-17deg BTDC). When the adjuster is moved to retarded (injection start valve open), the fuel is injected at 1.8deg BTDC (specified limits 4-0deg ATDC!!!). So if I understand this manual correctly, when the adjuster is set to retard the start of injection it’s not retarding it far enough!!

I’ve not managed to get hold of my friends locking pins for the engine yet, but once I’ve got these I’ll have a go at getting the timing back within limits & then report back on any improvement or otherwise.

Newbie Joined: Nov 06, 2005 Posts: 4

Sounds familiar to me with my A6 2.5TDi 5-cyl (AEL).
My water takes 20~30 mins @ 70mph to get to a steady 90C. The oil rises just as slowly and seems to settle about 80C, I feel that is a bit low.

VAG-COM states
1 Fault Found:
00550 - Start of Injection Regulation
17-00 - Control Difference

I don't know what this means.
When I do TDI graph it can't plot it because it is 'too advanced'! Opps.
I suspect the timing is out by one tooth on the belt. It was changed by the previous owner not me.
Can I check it with VAG-COM before I start opening the top of the engine for physical checks?

Although I don't have any cold start issues, my power sub 2000rpm is woefull. Above 2500 rpm and it rockets in all gears.

Has variant got to the bottom of the problem yet?

The closest my Googling got me to is http://community.dieselschrauber.de/viewtopic.php?t=8095&start=24
Cheers,
Matt

Newbie Joined: Jan 30, 2006 Posts: 12

One to watch out for:
I have had issues starting my car for some time now. In any situation it was hard to start unless it was fully warm.
After extended cranking a great plume of white smoke would come out and then the car would be down in power.
Using the vag com TDI graph, the timing was adjusted perfectly, but with the above results.
Took it to a garage and he said it was the timing (even though he made a balls of doing it.
I would also get these error messages:

VAG-COM states
1 Fault Found:
00550 - Start of Injection Regulation
17-00 - Control Difference - intermittant

Still with the timing issue, i checked the requested and actual timing in group 4 in measuring blocks and the timing was at 17.5 degress BTDC!
(TDI graph showed as good).
Adjusted pump to bring in to 3 degrees BTDC, and car now starting perfectly, power back to normal!

TDI graph is off the scale!!!

Been running ever since, and starts on the turn of a key. No engine knock, no lack of power, better fuel economy.
This procedure I borrowed from TDI club's method of checking timing. Not sure why it works but it does. See below for link.
http://www.tdiclub.com/TDIFAQ/TDiFAQ-7.html#k

Newbie Joined: Nov 06, 2005 Posts: 4

This looks very useful -thanks.
I got my timing 'sorted' by my garage to within the spec using basic settings and fields 2 and 9 in 000. Three weeks later the pump timing belt shredded! I fitted the new belt and tension roller, adjusting the adv/ret using the TDI graph to slightly above the mean. Starting wasn't as sharp as it should and there is a distinct dip or hesitation passing through 1400rpm. Fuel economy is disappointing too.
Tonight I'll look at the 'real' adv/ret readings in block 004. My logs from before indeed showed it at 17 deg. I suspect there is indeed a faulty sensor which is what TDi graph method uses but the real angle readings are more fundamental somehow?
Cheers,
Matt

Newbie Joined: Jan 30, 2006 Posts: 12

Hope it works out for you. As I said, my cars been running a storm ever since and starts on the button, with good power throughout the revs. I still have a minor issue though with air in the fuel line, but thats another story ill post up and see if anyone can come up with something.
Cheers!

Newbie Joined: Aug 25, 2005 Posts: 1

Guys

Stop using TDI timing checker with the 2.5 v6....!!!!!!!!!!!!!!!!!!!!!!!!!!!!1

Hope i got your attention here.........

My engine code is aym.....

toook mmmeeeee bloooodyyyyyy ages to get this sorted out.....

Tdi checker on mine, when i first put it back together was miles and miles out... so, i adjusated it to within what tdichecker said was ok.... wouldnt start, so strted playing around.... moved it back nearer and near to what it was when I put it back togther (should have legt it orig... seemed to work fine, fired up first time after a complete cam blet and injection belt change... lol)

After a while i found some info... bearing in mind my engine is aym.. you have to make sure your engine is warm, above 85 degrees.... but these are my instruections....

The proper procedure for AYM engine:

* Warm up engine, Check coolant temp in
Measuring Blocks Group 007, field 4.
- minimum spec 85C.
* Once 85C is achieved, go to Basic Settings, Group 004.
- value in field 4 must be 100%.
- value in field 2 must be "Late"
- timing in field 3 must be between 0 and 4 degrees ATDC.
optimum value is 2 degrees ATDC.

If timing is not within the specified range, adjust mechanically.

Any timing observations where this procedure is not followed are
essentially meaningless / invalid.

Got this from vag-com themselves....

I got the same errors when my timing was off, will never forget the time i went to my mates house.... car running well, seemed quite quiet.... parked up, few beers and chats... time to go home, cranking the car over.... the car parked behind me completely dissapeared in a cloud of white smoke, when i say dissapeared i mean really.... then the car started and i legged itout of there!!!!

Not just the noise of my cranking but the deisel smell must have been aweful...

hope that helps...

Newbie Joined: Jun 12, 2006 Posts: 19

It will be the pump timing.

I don't know about yours but the later ones you can adjust the pump a tiny amount as the bolts that holde the pully to the pump are grooved allowing for adjustment. i got it all mint with the timing pins but the pump timing pin didn't go in smoothly, i adjusted the pump timing literally 1mm and it started perfectly every time when warm after that.

p.s. how does th erwin website work, do you have to pay to be a member or something?