PD Startup Issues: Troubleshooting Guide

Hello everyone,

"A friend's PD-TDI engine failed yesterday. It's a 100hp PD engine in a Golf 4, so it should be an AXR, right? (Where are the PD engine experts?)"
According to his account, the starter motor spun the engine, but the engine stubbornly refused to start. It was only when he was on a downhill slope, using the starter motor to get it going and then rolling, that he was able to start the engine.
In my opinion, this indicates a starter motor speed that is too low (possibly due to a dead battery or problems with the starter motor contacts).
Now, my question to the PD faction: Do the PD elements only start injecting at a certain minimum speed, or does the injection occur immediately, regardless of the engine speed?
If the Electronic Stability Control (ESC) requires a minimum engine speed and that minimum is not reached, then this could very well explain the problem mentioned above.
I haven't been able to read the error codes yet, but I might do so tomorrow.

What other typical PD (Parkinson's Disease) symptoms could be the cause of the refusal to start the engine?

Regards,
Alex.

Hello donalexo,

I suspect that one of the pumps supplying diesel to the PD engine is malfunctioning, or that the diesel filter is clogged. There's a pre-feed pump at the tank and a tandem pump at the engine. When the ignition is turned on after a long period of inactivity, you can hear the pre-feed pump making a 'sloshing' sound as it pumps a cupful of diesel forward.

You can check the LongLife battery using the 'magic eye'; if it shows a green color, everything is okay, but if it shows a black color, the battery is discharged or defective.

Best regards, Marcus.

'Magic Eye'... throw it in the trash, it tells you nothing about the capacity, only about the voltage!!

'Having experienced starting problems with three PD_Golf4 (AJM, AXR) vehicles within the last month among my acquaintances, it was definitely the battery that was suffering from a lack of capacity. The starting problems are exactly the same as those seen in VEP-TDIs.'

A pump failure or malfunction would not only cause starting problems.

Check the engine compartment for leaks (diesel smell). I've already found some leaky hoses, the radiator, the diesel filter, and connections.

Julian wrote:

Because I had three PD_Golf4 (AJM, AXR) with starting problems in my circle of acquaintances in the last month, it was definitely the battery that was suffering from a lack of capacity. The starting problems are exactly the same as those seen in the VEP-TDIs.

Do PDs (presumably referring to a type of vehicle or engine) also experience the phenomenon where the warm-start behavior fails first, while the cold engine still starts well?

Hi Ulf!

Yes, it's exactly like with the VEPs (based on my experience). My acquaintance from Vienna couldn't start the warm engine (AJM); when it was cold, it started relatively well.
Two weeks later, the battery suddenly died overnight and completely stopped working.

However, he later told me that the engine had been starting very poorly when warm for almost three-quarters of a year.

Recommendation: Install the Megapulse!

Julian wrote:

Recommendation: Install the Megapulse!

What is that *likely behind the moon appearing* ?

@ulf

www.novitec.de

or

/viewtopic.php?t=1419&highlight=megapulse

It works great...

joergs wrote:

/viewtopic.php?t=1419&highlight=megapulse

Ah yes, I added my two cents to that thread...

Hello everyone!

First of all, thank you for your responses!
I also initially thought it might be related to the battery. Unfortunately, no one has yet answered one of my most pressing questions.

Does the PD (presumably referring to a specific type of injection system) only start injecting at a certain minimum speed?

That would be particularly interesting in the context of a battery with low capacity.

THNX

Regards,
Alex.

Magic Eye... throw it in the trash, it tells you nothing about the capacity, only about the voltage!!

Not even that.

It only indicates that in THIS SPECIFIC CELL, the acid concentration is within an acceptable range.


@alex

I'll take a look at a few PDFs tomorrow.


CU Gremlin.

hello alex,

'While I can't give you a definitive answer, I know that newer models have a kind of safety feature that prevents the engine from starting if the battery voltage is too low. Apparently, many models from various car manufacturers now have this safety feature. This information comes from a contact of mine who works for ADAC. He often encounters this problem and can't always help with jump-starting. Car dealerships have power modules that can provide the necessary charging and starting current for a short time. My TÜV inspector drives an Audi Allroad and can tell you all about this problem.'

joergs wrote:

However, I know that in newer models, a kind of protective function is implemented that prevents the engine from starting if the battery voltage is too low.

And what or whom is this function intended to protect from what kind of damage?
The workshops and battery dealers facing poverty?

When the voltage is too low, the control units will initially shut down.

Below a minimum voltage, the watchdog timer activates and resets the control unit. If the voltage is insufficient to power the power supply and output stages, it could cause serious problems.

If the minimum voltage is below the required level when starting, nothing happens except that the starter motor will turn.

However, overcoming that obstacle should then be no problem.

CU Gremlin.

Gremlin wrote:

Below a minimum voltage, the watchdog timer triggers and resets the control unit. If the voltage is insufficient to power the power supply and output stages, it could otherwise cause severe reactions. If, when starting, this minimum voltage is exceeded, then nothing happens except that the starter motor turns...

Okay, this is the minimum voltage required by the "system," which, in the age of PCs, really doesn't need any special mention – unless this minimum voltage would still allow the starter motor to spin freely and easily start a mechanical diesel engine.

However, I understood what Jörg wrote to mean that the system is "unnecessarily" being blocked from starting up when the voltage is still significantly higher than the minimum required for the STGe (Smart Transformer Grid Edge) to function.

Hi,

For some engine control units, the threshold seems to be quite high... with ABS, it's supposedly 10 volts. I've also observed this in the winter - a long pre-glow period, then starting the engine, during which the voltage drops briefly below 10 volts, even with relatively new (2 years old last winter) batteries. The result is visible in the ABS indicator, which then signals a self-test, which is a side effect of a restart.

It would be interesting to know where this limit lies in the engine control unit.

"With the dead battery in my parents' Passat, I saw via VAGCOM, using the MSG (Module for Engine Management and other functions), that the voltage was below 8 volts (something like 7.x...) (in the corresponding measurement block), and I was still able to access the measurement values, so the MSG was still running. It only crashed when I tried to start the engine – but at that point, the voltage probably also dropped towards 0. However, it was a 1.8T, so something different might apply to our MSG."

Best regards,

Jan.

Hey guys!

My AJM has also been giving me trouble for a while! It starts fine when cold, but it's a bit difficult to start when warm. And if I forget to turn off the (parking) light for a couple of hours, it's even worse.

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