Warmstart 5Zyl TDI (AEL) problematic

Hello

a very rare problem that I've had on my TDI since I bought it; neither in winter nor when the engine is cold, the car doesn't start well - but once the engine is warm, it just needs longer to start. I haven't encountered this with any of the 5-cylinder engines. TDi (had about 10 of them) - but honestly, it's not a huge problem either - but it's abnormal, so I wanted to ask.

Now, I'm starting to wonder, what could it be? I always thought it might be related to the temperature sensors - but the coolant sensor is new and provides plausible values - and the head gasket is also new - so I initially thought it was related to the faulty head gasket (if there's pressure in the system and I stop the engine, the water would push into the cylinder, that's why it needs a little longer to start up next time) - but that one is also new, as well as the timing belt and, of course, the pump is also properly adjusted.

Last time, after about 1 hour. Could I measure the fuel temperature at the ESP sensor at around 30°C outside temperature? The sensor indicated 68° - Is it plausible that the diesel, with approximately 45 liters remaining in the tank, could be so "hot" after an hour of driving - or is it the sensor that is giving a false reading?

Regarding the question - what else could be a significant factor causing the TDI to start poorly when the engine is warm?

Thanks for the tips

Best regards, Uwe

In my case, the poor starting performance was mainly noticeable in cold weather, but this issue disappeared after I had moved the starting point further forward than recommended.

Quote:

To the question - what else could be a decisive factor that the TDI engine starts poorly when warm?

Possibly. Low starter speed, resulting in delayed start approval.

If you still have the old Temp sensor, you could try placing it nearby the warm engine to simulate a low temperature. If you only disconnect the connector, the ECU will probably only generate a replacement temperature. Try.

Hi

Thank you for the tips. Regarding the starter - I had also considered that, and the starter could be the problem after 500,000 km, or that the cables etc. might be worn out. However, wouldn't it be necessary to be able to hear that the starter is having difficulty? I always hear a well-functioning starter motor when starting the car, which sounds consistent (in terms of speed).

I'll give the temperature sensor a try, thanks for the tip.

Greetings

You need data, your ear, sorry for that, doesn't work, because: you drive the car regularly and don't notice the slow, steady wear and tear / decrease in performance. Should there be a minimum starting speed, it is sufficient if your starter is just slightly below that...

Quote:

To the question - what else could be a decisive factor that the TDI engine starts poorly when warm?

Fuel pump flow rate is too low. What fuel injection amount does VCDS display at the engine idle (warm, without major electrical loads)?

Best regards, Rainer

YES, that's correct. I'm going to test the temperature sensor right away.

Is it sensible to measure the RPM during starting? I can certainly try...

Okay, so, ich kann mir die Sache mit der Startdrehzahl sparen, da ich jetzt den anderen Sensor angeschlossen habe - DANKE FÜR DEN TIP - dieser hatte dann 30°, dann startet der Wagen auch ganz normal - mit dem Sensor im Wasser (90°) braucht er eben länger.

It's not a major problem, although it's not normal - I haven't experienced this with any other TDI, and my current one is doing it now. It's not getting worse - therefore a luxury problem - but still interesting.

Therefore, I don't think I can really change anything, as with VOLVO, you can't make any adjustments (e.g., increasing quantities) - I will have to accept that. This likely relates to the pump. 500,000 km is also not insignificant for a part like this. However, I won't know for sure until I repair or replace the pump.

Here's the translation:

"And also, the following visual/acoustic documentation:"

Warm start at 30° on the sensor --> https://www.youtube.com/watch?v=1u73wV8s1tE
Warmstart at 90° on the sensor --> https://www.youtube.com/watch?v=sbE2Q7Di_Xs

Thank you.
Best regards, Uwe

Please upload all;-) attachments in the topic, thank you!

Hello,

Take a look at the locking screw on the high-pressure part. Depending on the extent of the damage, you may only experience issues with warm starts, or also cold starts (valve adjustment).
I've already had several pumps with this problem.


See the image in the attachment!

Screw and O-ring number available upon request... costs around 15€;

roorback wrote:

Is it sensible to measure the RPM during starting? I can certainly try...

Hi!
So, I had the warm-start problem with my 1.9 Golf ALH,
Ultimately, it was the battery that caused the problem, definitively.
In the winter, at -15°C, it started immediately. However, in warmer conditions, it didn't start right away.

The engine speed isn't reaching the target, I think it needs to be 300 RPM.
Likely to protect the two-mass crankshaft.

After watching your videos, I don't believe it,
When I started my Golf, it took significantly longer to warm up. I'd say it was about 10 seconds.

vwSchrauber wrote:

Hello, Take a look at the locking screw on the high-pressure part. Depending on the extent of the damage, you may only experience issues with warm starts, or also cold starts (valve adjustment). I've already had several pumps with this problem. See the image in the attachment! Screw and O-ring number available upon request... costs around 15€;

Hello VW enthusiast.

Can I please ask you about this topic again; what type of screw is it and how can I identify any damage? Although I have already disassembled pumps to completely seal them, I haven't worked on the high-pressure part, and I also didn't know that something might be defective there.
I have reassembled the part exactly as shown in the picture (with the new O-ring).


Thank you.

Hi,

This is the three-pronged locking screw between the high-pressure outlets. If this has broken, then you have a leak between the high-pressure and pump internal pressure. It is not noticeable from the outside, as nothing (exteriorly) leaks, but at the low starting RPM + small initial amount, the nozzle opening pressure may not be reached or only after several pumping operations.

Okay - thank you very much.

Then I'll take a look at the high-pressure part...

Autoservice wrote:

To the question - what else could be a decisive factor that the TDI engine starts poorly when warm? Quote: Maybe Low starter speed, resulting in a delayed start release.

Exactly that was also the problem with our Ford Galaxy TDI with AFN engine: it started perfectly cold, but every second warm-up was associated with Orgelei.

Online, one found new battery and starter to increase the starting RPM, but this only works temporarily and then the organ playing starts again.

But I also found a tip to re-code the engine control unit switch to automatic , the reason is that with the automatic, the starting release comes at a lower engine speed.

I've added my 1551, and it's been coded and working perfectly for 2 years.

The only drawback (which, fortunately, doesn't apply to us) is that the GRA no longer functions.

While not necessarily a 100% perfect solution, it cost me 0.00 Euro and helped.

Best regards, Rüdi

Now - at VW, it is supposedly possible to program the quantity increase in the control unit - but not at VOLVO.

And - the fact that you're satisfied with the "AUTOMATIK" transmission surprises me quite a bit - I had tried that on my VOLVO once - the automatic transmission there is much slower and also provides intermediate gas during gear changes - which made driving really difficult.

Greetings