VW Polo Starting Problems: 1.4L TDI PD Engine

Hello everyone!

"Lately, my Polo has been starting very poorly after being parked for a long time (more than 10 hours). I have to crank it for ages every time."
To me, it sounds like there's a leak in the fuel line, which is allowing air to enter and causing diesel to flow back into the tank.
Based on the information provided in these help sections, it could also be the hall sensor. However, considering my observations, I find that unlikely.

What do you think about this? Can I check the hall sensor using VCDS?
And the more pressing question: what is the best way to check the fuel system for leaks?

Thank you and best regards.

Have you checked the coolant temperature (as detected by the MSTG)?
When the display shows "warm," it may be necessary to prime the system until the full capacity is released.
Quick test: Disconnect the temperature sensor - then it should start immediately.

Best regards,
Micha

Also check: The sealing rings on the fuel filter return line (if present, varies depending on the vehicle).

Wiesel wrote:

Have you looked at the (coolant water temperature) that the MSTG detected? When the display shows "warm," it may be necessary to prime the system until the full capacity is released. Quick test: Disconnect the temperature sensor - then it should start immediately. Best regards, Micha

.

Great, thanks for the tip!
I'll try it out and let you know how it goes! XX

dieselschrauber wrote:

Also, also check: The sealing rings on the return line from the fuel filter (if present, varies depending on the vehicle).

Thank you very much!
I don't think there are any sealing rings present.

stolley wrote:

dieselschrauber wrote: Also, also check: The sealing rings on the return line from the fuel filter (if present, varies depending on the vehicle). Thank you very much! Seals are there, but I don't think they exist.

Are you sure? I mean the T-piece that is inserted depending on the type of filter being used.

If the previously described options do not lead to a solution,
Unfortunately, there are still some leaky pressure dividers (PDs). Let's check the values of the idle speed control to see if we can identify anything.

Hello.

Please check the rubber fuel lines that run from the filter, over the cylinder head, to the tandem pump for cracks.
I had to replace it in my Lupo 1.4 TDI before; I experienced the same problem. Since the replacement, I haven't had any issues.
Is there a complete repair kit available from Volkswagen that includes the metal lines and fuel sensor?
Of course, you can also buy NBR hose by the meter and purchase good clamps to assemble it yourself.

However, a leaky tandem pump can also cause these symptoms. Some leaks are visible externally, while others leak internally into the oil circuit, which is not immediately apparent but can be detected by the smell of diesel in the engine oil and by an increasing oil level.

The "Knackfrosch" (a plastic T-connector) is no longer located inside the filter housing of the 9N; instead, it's housed in an external metal casing on the right side of the dome. The filter for the 9N now only has 2 connections.
The water separator wheel with the seal at the bottom of the filter is another potential source of air leaks.

Regards, Mpire.

Hey everyone!

Thank you very much for the helpful suggestions!
According to VCDS, the coolant temperature sensor is currently indicating a pleasant 26.7 degrees Celsius.
So, he can't be the one.

Currently, I'm having a problem because I seem to have drained the battery, so I can't attempt any more starts. I already replaced the rubber hoses in the supply line after the filter. Currently, I've replaced the hoses in the return line (up to the aluminum pipe).

The pressure gauges were reading normally last time I checked, but I'll check them again. Could the leak (if there is one!) be located in the area of the tank?

Best regards!

stolley wrote:

Hi everyone! The pressure gauges were reading normally last time I checked, but I'll check them again. Could the leak (if there is one!) be located in the area of the tank?

With the help of my T5, I finally managed to get the Polo started – after a long time of struggling.
On that occasion, I checked the product descriptions.

Code:

Samstag,06,Juni,2015,21:48:14:25065 VCDS -- Windows-basierter VAG/VAS-Emulator VCDS Version: RKS 14.10.2.0 Datenstand: 20150412 http://shop.dieselschrauber.de Fahrzeug-Ident.-Nr.:    KFZ-Kennzeichen: Kilometerstand:    Reparaturauftrag: Verdrehwinkel+LRR -------------------------------------------------------------------------------- --------------------------------------------------------------------------------                 Adresse 01: Motorelektronik  (045 906 013 E) 21:49:07 Block 013: Leerlaufruheregelung (Einspritzmengenabweichung)   -0.54 mg/H  Einspritzm.-Abw. Zylinder 1   -0.07 mg/H  Einspritzm.-Abw. Zylinder 2   0.56 mg/H  Einspritzm.-Abw. Zylinder 3

They should be okay, right? Not bad for 279,000 km, wouldn't you say?

Looks good. I think you just need to find the spot where air is getting into the fuel system.
One more thing: If you need to troubleshoot something again, try checking if you can access the engine control unit via diagnostics, or see if the displays in the dashboard are different than usual. This is just to make sure that, for example, the engine control unit isn't malfunctioning due to a lack of power.

Quote:

Not bad for 279,000 km, right?

... well, even with the mileage, it's still not possible to completely rule out potential issues with the pressure distribution (PD).

Autoservice wrote:

Quote: Not bad for 279,000 km, right? ... well, with such high mileage, it's still not possible to completely rule out leaky pressure distributors.

You're right about that too.
But shouldn't that be reflected in the LRR?

"In any case, I can't detect any increase in oil level or engine oil that smells like diesel."

I also remember the fuel cooler located on the undercarriage. Let's check the connection couplings and the cooler itself for leaks.
It is possible that damage could occur there through impact or similar actions.

Check if the pre-lift pump in the tank activates when you turn on the ignition.
When the hoses were cracked, the pump would always make gurgling noises when I first turned it on. Since replacing the hoses, those noises have disappeared.

Regards, Mpire.

Hello everyone,

Has anyone also thought about the PD cable harness? It's naturally located in the oil... Just a thought from a newbie .
Greetings from the Eifel region.

Hello everyone!

I haven't heard from you in a while, sorry!
The fuel hoses in the engine compartment have now all been replaced.

It still sometimes struggles to start, especially when the fuel tank is nearly empty.
Does anything come to mind?

Best regards,