T5 AXB Kaltstartproblem (Schlauchkupplungen undicht) | Posts 16+

After the fact... Thank you for the feedback .


Edit: Reopened upon request .

Hello,

Unfortunately, the problem hasn't been solved.
After 2 months of no issues, the morning starting problem is back.

I have now also replaced the connector on the supply side, near the tank, on the differential pressure sensor.
Unfortunately, without success.
BTW: The clutch return line on the tank side is only available as part of the complete hose assembly.
Therefore, it has not been renewed.

The problem:
When starting the engine from cold, it starts for about half a second and then immediately shuts off. After about 10 seconds of cranking, it starts and runs. Initially, it runs a bit rough, but after 3-4 seconds, it runs smoothly. However, the idle speed is then higher than normal.
Does anyone know why the rotational speed is being increased?
Or, what factors usually lead to this?

Based on my observations over the past few days, it appears that the pre-feed pump in the tank is not starting in the morning. I think I will either replace it or, at least for now, remove it and check it.
Does anyone happen to know how I can get in touch with them?
Does the tank need to be removed?
Can it be done without a pit/stage?

The T5 was manufactured in May 2005 and has an auxiliary heater.
The funding code should be 7H0 919 088 B.
Does anyone know if other sizes are available?
The part costs over 200 EUR at the .

Regards,
Nick.

Before you buy anything, be sure to thoroughly check the function. The pump should be located on the driver's side, in the area between the second and third rows of seats. So, if there's an access point from above, there should be some kind of cover underneath the carpet or floor covering. That's usually how it works.

You can also run the pump using VCDS. Otherwise, you'll have to observe its function using a test lamp. Unfortunately, I don't have any wiring diagrams, so I can't tell you where the best connection point would be.

Hi,

As far as I know, there's no hole in the floor panel of the T5.
I had already searched for this some time ago.
Der Tank ist ziemlich weit vorne so auf Höhe der 2. Row of seats.

Actually, I don't want to buy anything yet; I first want to check the cables and connectors, and then remove and clean the pump unit.

I couldn't access the pump using VCDS, in my opinion.

Regards,
Nick.

Quote:

With VCDS, I was not, in my opinion, able to access the pump.

Wasn't it missing in the actuator test, or did nothing simply happen?

Normally, the pump always runs when the ignition is turned on - sirr - gurgle .

Hello everyone!

To begin with, I don't think the pre-pump has anything to do with it...
When the ignition is turned on, it runs for about 5 seconds, and once the air bubbles are gone, you can't hear it anymore - but it still runs!
Check the couplings again and replace the DiFi (differential) once more. The error must logically be located somewhere in that area, since it started working again after some tinkering .

If you still want to do it:
The fuel tank needs to be removed from the T5. It can be done without a lift, but having a helper and jacking it up on the left side would be beneficial. IMPORTANT: Make sure to empty the tank as much as possible beforehand, because 80 liters of diesel also have a considerable weight .

Best regards from Munich!

Hm, I'm not sure if I was able to select the pump during the actuator test. But it doesn't really matter, since the pump is running anyway when terminal 15 is energized. What should the test actually look like?

I'm almost certain that the pump won't start when the error occurs. Otherwise, I hear the pump every time the car has been standing for an hour.
I need to pay more attention to that again tomorrow morning.

According to that, the gurgling sound is normal, right? There shouldn't actually be any air in there. The quick-connect couplings have check valves.
Replacing the DiFi again is an option; since the couplings are new, the problem might be with the corresponding part/filter.

I'm also not keen on removing the fuel tank, but after 282,000 km (approximately 22,000 liters of diesel have passed through it), there's bound to be some dirt and sediment in there.
The fuel sensor isn't working properly anymore. It seems to be reading too high.
That's why I suspect something.

In the default setting of the T5, the battery lasts for approximately 30 seconds at a time, and the tank is completely empty in about 25 minutes.

Uff, you're of course right! Like always .

The pump starts running when you turn the ignition on in the morning, but then it stops.

The pump can indeed be controlled as described by Klahaui.
(not a final control element test!)
I did that today too.
Ignition on -> pump starts.
"With the pump in its default position, it was turned on (it's audible, making a gurgling sound)."
(This means the pump is not permanently powered on via connection Kl15, but switches off again.)
Then it started.
With a good shake, the van started and ran with an increased RPM (approximately 1300 RPM).
Pump turned off again -> speed drops.

After that, a test: With the engine running, turn on the pump -> the RPM will increase.
That solves the mystery of the speed boost.

Okay, now I need to find the leak.
DiFi costs over 40 EUR , and I don't want to exchange it directly again if there are other possibilities.

Does anyone have an overview of the fuel system?
Are there any other separation points in the upstream process?
Could the fuel tank high-level sensor (STHZ) potentially drain the system? Or is it directly connected to the tank? (There's a separate pump module for vehicles with auxiliary heating.)

I am grateful for any advice!

Regards,
Nick.

What are 40€ worth compared to the headache of endless troubleshooting, if this is actually the error ?

Are the PD elements really okay? Unfortunately, they often get stuck in the head.

Yes, you're right! *grumble*

Hab gerade nen neuen Filter bestellt. (Orig. VW for €46.

The problems with PDE/ZK are typically only seen in 5-cylinder engines.

I had suspected the wiring harness for the power delivery elements (PDEs) before, as I occasionally experienced slight jerking during load changes in the partial load range. However, I haven't noticed it for a while now...
Could the wiring harness theoretically be related to the starting problem?

Regards,
Nick.

Quote:

Could the wiring harness theoretically be related to the starting problem?

It's rather unlikely, as it would require all the power circuits of the PD elements to be affected simultaneously.

Hello,

The problem has now been resolved since the weekend.
The car, which had been standing for only a few hours, finally started after a few seconds of cranking.

And the winner is: alevuz!!!!

ZK defect, PDEs heavily integrated.
Cylinder head and tandem pump replaced.
Including small items, the material cost is 1600 EUR.
Hopefully, it will stop there.

Interestingly, the fear of this kind of damage was the main reason why I opted for an engine with a different number of cylinders. However, the AXE engine is simply fantastic to drive in the Bulli.

Well, hindsight is always 20/20.

To all of you, thank you very, very much .

Regards,
Nick.

PS
For completeness, here's the post about the stuttering issue after the head swap:
/viewtopic.php?t=28087

Thank you for your feedback!

Quote:

The problems with PDE/ZK are actually only typical for the 5-cylinder engine.

For the sake of completeness: the PDE (pump-injector) system affects the combustion chamber in all engines with two-valve technology to a greater or lesser extent. In the case of the five-cylinder engine, the externally located fuel lines also add to the potential sources of error.