UK-POLOS.NET - THE VW Polo Forum

I've got a Polo 6R that has me punching the air right now.

The car cranks fine but wont start, After doing a bit of diagnosing I've found out that the fuel pump doesn't seem to be doing much of anything right now, probing at it with a multimeter it doesn't seem like it's getting any power with just trace voltage measured between the main two wires at the main fuel pump relay, I also can't hear anything when I switch the car on nor do I feel any of the normal mechanical vibrations coming from it when I try starting the car. So it's somewhat safe to say that the pump ain't pumping.

First thing I did was swap the battery, it was ancient anyways and needed replacing.
Next thing was of course to check the fuses. I went over every single fuse and only found one blown fuse which turned out to be the fuse got the rear wiper blade (So at least thats working again now)
With every fuse confirmed OK my next thought was relays, I went and grabbed out the 2 449 relays from under the dash which I know one of em controls the fuel pump, they seem fine visually speaking and normal resistance measured on the coils, I tried swapping them around just to test and still just the same so I'm doubting it's the relays.
Eventually I just said f**k it and replaced it with another fuel pump as a mate had a compatible fuel pump he wasn't using, was a hail mary but at least I can very much confirm the issue isn't with the pump itself.

I've looked around for loose wires and such but I've been unable to find anything that looks awry, the car worked mostly fine before hand but in the months leading up to this it had been struggling to start, taking a good few seconds before starting properly, the car then got parked for about 2 months and when I went to start it again I encountered this issue.I'd be surprised if it was a wiring issue as I find it somewhat unlikely that wires would just fall apart with the car sitting in a parking lot

Right now I'm kinda just at a thinking stage, I've gone through the most obvious stuff and I'm not exactly the most mechanically gifted person, I'm alright with a screwdriver but lack the experience to be properly confident with cars.

Hi welcome, I suppose you should comment on which engine you are talking about so that the forum users can help you or give you some advice.

Due to the '449 relays' we can imagine the manufacturing dates of your 6R (2009/2012) but it would also be convenient if you tell us the manufacturing date.

Measuring the resistance of the relay coils does not imply that the relay is working correctly... you can use a 9v battery that you have in an appliance at home to energize the coil on the small terminals of the relay and hear the 'click' of the internal contact and in turn check the continuity on the large input and output terminals.

If you have a diagnostic tool, a scan would be great... although we assume you don't have any.

We also assume that in Iceland the ambient temperatures at this time are pleasant, maybe some mustelid (Mink), or rodent, has eaten the proper wires after leaving the car parked for two months.

Thank you so much for the reply

Engine is a 2011 1.2L TDI I3 with the car being Manufactured in late 2011

I went and tested the replays properly, very clear click and continuity was good so the relays seem to be working properly, with a bit of contortion I was able to feel the relay click when I turned the car on so it also seems to be energized fine, so from my pleb point of view it seems whatever issue is happening it's after the relays.

I'd personally doubt a rodent or any other animals would have eaten any wires, in general we don't get anything larger than mice and the very occasional rats around here and they seem to mostly leave cars alone, the area the car was parked in has had cars standing there for months on end for years and years without any issue with small animals gnawing at wires.

I don't have a scan tool but I'd be willing to invest in one to get this sorted, is there any brand / model that is generally recommended around here?

Due to the symptoms mentioned, it is possible that J179 Automatic glow period control unit or one of the glow plugs is failing.
It's just a guess, with a diagnostic tool it could be verified.

First check that the 50A SA7 fuse on top of the battery is not blown. J179 is powered by this fuse.

VCDS is a good diagnostic tool.
There are many others, all of them can detect faults (DTCs) and clear them.

Checked all SA fuses, all measured good. Out of curiosity I did just straight up remove the J179 from the car and see if I noticed any difference.
Car failed to start in the exact same way, engine cranks and did spurt to life for a few moments but quickly died, same as always.

I got myself a standard bluetooth OBDII reader since that was all I could have delivered within a reasonable timeframe, zero fault codes detected.
Only thing that caught my eye was the Throttle Position Manifold which is hard locked at 90% and didn't move at all, pressing the throttle pedal in had no effect, however this might just be some weirdness in the Torque App since diesels don't really use a throttle in the same way the more common petrol cars do

It is rare that no fault is detected in the diagnosis.


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If the J338 throttle valve module failed, I assume that the failure would be detected in the diagnosis of the ECU.
Hmm... out of curiosity, check if Torque App can do the basic setting/adjustment of J338, or an output test.

Examples;
https://www.youtube.com/watch?v=BSbz5PX91tQ
https://www.youtube.com/watch?v=5AvuvjpotNU

Sorry to necro, but in case someone else runs into this at a later date I'd at least like the fix to be here as well.

The issue was with the Immobilizer, I'm not sure what caused it but the immo was rejecting the key, After towing it to the local VW dealer they reprogrammed the immo and it started up and ran like a dream.

It's never too late...

Thanks for the contribution, fortunately the workshop was able to diagnose it and see how surprising some 'breakdowns' are.

Aurastyx wrote: Tue Nov 19, 2024 2:56 pm Sorry to necro, but in case someone else runs into this at a later date I'd at least like the fix to be here as well.

The issue was with the Immobilizer, I'm not sure what caused it but the immo was rejecting the key, After towing it to the local VW dealer they reprogrammed the immo and it started up and ran like a dream.

Until you fixed the immobilizer, the car was parked ? You could not start it all ?
If managed to start the car, was the car running ok ?

Good morning,

yes when the engine starts and stalls it's typical vag, it's the immobilizer.