AFN Cold Start Problems

Unfortunately, my AFN engine is still not running as it should! Vehicle: Seat Ibiza, AFN engine, 319,000 km.

The problem was that the ESP (Electronic Stability Program) was either activated too early or too late, which resulted in either black smoke and loss of power, or extremely poor starting performance.

I now have the full VAG-COM software, and yesterday I adjusted the pump again to the 'optimal' setting! Specifically, the basic settings for control module 000, field 2 is now 45, and field 9 is 140, representing the temperature.
MWB field 1 and 2 are perfectly consistent across all load conditions!

'Despite everything, the car still starts very poorly! The glow plugs were checked and are okay! It starts fine when warm, but after about 2 hours, it starts poorly. This problem has been happening for about 4,000 kilometers. Previously, the fuel injection timing was set too early (field 2 was at 90), which caused no starting problems, but resulted in smoke and a loss of power!'

I've noticed that the timing belt (Continental, approximately 60,000 km) seems to be able to be pushed about half a centimeter towards the idler pulley without the tensioner pulley moving. When I apply more pressure, the tensioner pulley works normally. The belt returns to its original position, directly opposite the marking. Could it be that the belt has stretched? Or what could be the cause of this?

Boro wrote:

A warm start is also okay, but after about 2 hours, it starts poorly!

The problem has been occurring for about 4,000 kilometers! }
Can air be excluded from the pump, which may gradually seep in through porous pipelines, for example?

Test: Insert a clear tube into the return pump -> install the filter and check for bubbles while the system is running.

The fuel lines were replaced last year when the injectors were changed, so I'm ruling that out. Also, if I advance the timing slightly, the engine starts 'almost' normally!

Does anyone know if it's normal for the timing belt to look so loose??? I seem to remember it always being quite tight! Otherwise, I'll just buy a new one for €46 and replace it sometime this weekend.

Quote:

I've noticed that the timing belt (Conti, approximately 60,000 km) can be pushed about half a centimeter towards the idler pulley without the tensioner pulley moving? When applying more pressure, the tensioner pulley works normally! The belt returns to its original position, directly opposite the marking! Could it be that the belt has stretched? Or what could be the cause of this?

The belt naturally has some flexibility. If it doesn't have any tears in the internal material and the tensioner isn't stuck, it seems to be okay.
However, if it starts to stretch like an old V-belt, I would replace it.

Here are some more options, in case the above does not apply:

Are the valve timings and crankshaft gears okay?

"Hmm, at that mileage, it might be a good idea to check the engine compression."

Relay 109 cannot be completely ruled out either; it may no longer function correctly once a certain battery voltage is reached.

It's somehow like it's cursed! Yesterday, I adjusted the pump again; it was set to a much too late timing, although it was adjusted the day before yesterday ???! After a lot of fiddling, the injection amount is now at the upper tolerance limit, so a little more towards early timing!

The car otherwise runs perfectly and has good pulling power, with almost no oil consumption!

This morning, it was sputtering again, but it seems to clear up after about 5 seconds. It stutters with white smoke and then runs normally.

The transmission gear was replaced three weeks ago, it was re-machined using this milling machine, and a new one was installed! I've also already replaced the R 109; no change.

I checked the beer lines again and replaced one that seemed porous.

Performed actuator diagnosis again using N108, and observed a noticeable change in engine running. In the measuring block 000, field 2, the value changes smoothly from 0 to 255!

KW, NW, and pump are located on the OT (or in the markings/locking mechanisms).

'Previously, the pump was out of specification and running extremely early. Does this mean it will now start normally?'

Okay, I'm going to change the belt this Saturday and take my time to adjust everything to the optimal settings!

Boro wrote:

It's like it's cursed somehow! Yesterday, I adjusted the pump again; it was set to a much too late time, even though I adjusted it the day before yesterday ???! !

This type of witchcraft is often called "loose KW pinion gear" - even if it has just been (apparently) repaired .

Here's the latest update!

This weekend, I replaced the timing belt myself! The old one was already significantly longer and worn out on some of the teeth (you could already see metal fibers).

The engine runs great after that, but it still starts with a puff of white smoke!

Yesterday, I had the crankshaft sprocket checked again at a VAG authorized service center.
'The crankshaft stub is okay, and the crankshaft gear (2 weeks old) is okay! The valve timing was supposedly adjusted again! Yesterday, it started poorly again after only 3 hours of standstill.'

This morning, the temperature was around freezing, and after four attempts at pre-heating, it started almost normally! It just runs a bit rough for a while, then fires up briefly like it's only running on one or two cylinders, before finally running on all cylinders.


The workshop suspects either a problem with the glow plug system or a faulty head gasket! However, I can't detect any coolant loss, and the glow plugs seem to be working fine. According to the voltmeter, the on-board voltage drops to 10.5 volts during the preheating phase and for about 5 seconds afterward! This suggests that the glow plug system itself is likely functioning correctly.

'Does anyone have any other ideas what it could be? Could it be a faulty valve in the pump?'

For the older "boxes," the battery, starter motor, and corrosion on the starter motor wiring/ground straps are also significant issues. If the starter motor speed is too low, the engine will be very difficult to start, even though it seems to be spinning well. Disconnect the positive and ground cables, clean them with a wire brush, and reconnect them. Then, check and charge the battery. The next cold start will show if that was the problem. It's not a big job.
There are plenty of starters that fail during operation. Anything that doesn't conduct electricity properly when starting will get hot.

Best regards,
Christian.

I also experienced the issue where my automatic fuel nozzle (AFN) became increasingly difficult to start after a longer period of inactivity (more than 1 hour). In the morning, it could sometimes take up to 5 seconds to start.

The cause was clearly a slightly leaky fuel line running from the tank to the ESP (Electronic Stability Program).

Even after being sealed, the problem reappeared almost immediately after a few days of inactivity.

Question for the pump specialists here!

Can anything in the fuel injection pump fail that could cause these symptoms?

I can definitely rule out the crankshaft pulley... I set the shaft to Top Dead Center (TDC) and made my marks! I checked it multiple times, and the marks were always in the same position!

'The head was replaced 60,000 km ago, and there's no coolant leakage.'

'The problem persists: the engine cranks for 2 seconds before one cylinder fires, and then the others follow, producing a white/gray, smelly cloud. After driving a short distance (about 700 meters), the exhaust becomes warmer, and when I stop, it cranks again. When the engine is warm, it runs perfectly, with normal power, reaching 215 km/h with the stock settings. After an hour of trouble-free driving without any smoke, it starts fine. However, after 3.5 hours of driving in 15-degree Celsius weather, it cranks again.'

It all started when I had the KW gear checked during an oil change. A new one was installed, and the shaft was machined. However, there were no particular anomalies; the gear showed slight pressure marks from the shaft. Afterwards, I noticed (using VAG-COM) that the injection timing was far too early, around 180. The car didn't show any other issues, and I don't know how long it had been like that. After adjusting the pump, the problems started. If I adjust the pump to a later timing, the car starts perfectly even when cold?

Diese Werkstatt hatte die Pumpe später nochmal mit der Messuhr eingestellt. Ergebnis, korrekter Start, aber wieder viel zu früher Einspritzzeitpunkt lt. VAG!

'The fuel pump has now been correctly adjusted by a certified workshop and, according to VAG standards, is almost perfectly calibrated! However, the problems persist, and strangely, the injection timing varies between 25-30%! Ideally, it should be 50%. If I start the engine cold and immediately go to the base setting, it almost stalls! The values in field 2 then immediately go to 000!'

I think something is broken either in or on the pump! Maybe a spring is broken or something else? Is it actually possible to misalign the impeller?

Does anyone have any ideas??


When you activate a consumer while the engine is idling, such as the air conditioning or power windows, the duty cycle increases rapidly! In my case, it goes from 30% to 39% when the air conditioning is turned on! If I go to the default setting beforehand, I currently have a value of 27 in field 2, and when I turn on the air conditioning, this value immediately goes to zero, or only 255 is displayed.

Is this actually normal?

Despite checking the crankshaft gear multiple times, I made sure the crankshaft was aligned with the transmission housing at the top dead center (TDC) position. I then marked the northwest side of the crankshaft and the pump wheel (including very fine markings). Regardless of whether I drove aggressively or stalled the engine, these markings always aligned perfectly afterward.

What was the target starter motor speed again? In a 001 model, with the pump connector disconnected, mine is running at 294-339 rpm, which isn't much either!

Could a faulty or contaminated oxygen sensor (OT sensor) be the cause of this? Where is the OT sensor located in the AFN engine?

Hello,
I believe the older TDI engines (1Z, AFN) do not have a crankshaft position sensor (CKP).

Greetings.
Reuselkopp.

Hi.

"On my DIY TDI (AHU 97), the problem was leaks in the fuel system. I fixed it by simply installing small check valves in the fuel supply and return lines, and since then, it starts perfectly every time."

Best regards, Rüdi.

'There's no air in the system! Unfortunately, I still haven't found a replacement pump, so things haven't improved yet!'

I read in this forum that a faulty pump suspension could be the cause.
I noticed that the 'bracket' on the left side/timing belt, which connects the rear screw to the front screw, is broken! But this shouldn't have such a significant effect, right???

Currently, according to VAG specifications, the injection pump is at the lower limit of the injection timing range, yet it's cranking for a long time with a lot of white smoke! It's slightly misadjusted despite the fixed crankshaft pulley! Prolonged preheating by disconnecting the coolant temperature sensor results in a rough start with little white smoke, but then the engine briefly revs up during a 'normal' start.

AFN now has 321,000 registered users.

Boro wrote:

I noticed that the "bracket" on the left side/timing belt, which connects the rear screw to the front screw, is broken!

But this shouldn't really have such a big impact, should it???}

"In my opinion, this bracket is simply a 'locking mechanism' to prevent the hidden screws from rotating when the nuts are tightened (or vice versa)."

Once everything is properly attached, you could potentially snap off the bracket (if you could reach it) without it causing any problems.