Defective Pressure Relief Valves: Causes & Solutions

Hello fellow mechanics!

Has anyone experienced one or more faulty pressure relief valves on the connection flange of their VP37?
I am particularly interested in knowing what symptoms occur when there is a defect in the equal pressure valves. These include the engine noise, the exhaust behavior (smell!!), and the engine's power output, etc.

Could a malfunctioning pressure relief valve mistakenly connect to a faulty heat dissipation system, or are the symptoms actually very different?

Thank you very much for your help.

Regards,
Alex.

Hello everyone!

Is there any experience with this? Do the check valves on the pump really not break, or has no one noticed because the effect is so small?

In theory, a faulty check valve should lead to a reduced fuel injection amount, which is also injected too late. Am I mistaken?
"Due to the pressure drop in the injection line between two crankshaft rotations, a portion of the injected fuel is lost due to the compression of the dead volume in the line. Simultaneously, the injection timing shifts later by the exact amount of time required for the compression. This could also explain the loss of power in a TDI engine, which can occur very gradually, or even sporadically, if the check valve sometimes sticks and sometimes doesn't."
Can anyone confirm or refute this theory?
Are there any opinions on this?

Thank you for your posts.

Regards,
Alex.

Hello Don Alexo,

It seems to me that the ESP itself is a kind of 'sacred cow,' something that only 'super professionals' should work on. I also had a lot of trouble and stress when I first messed with the ESP, having little knowledge but a lot of enthusiasm. Due to various 'horror stories,' I wouldn't dare to tamper with the internals right now, and neither would most others.

'Means to say:' or 'In other words:'
If problems arise that are attributable to the ESP-DHK system and cannot be resolved through adjustments or replacement of the DHK, then the system is diagnosed as 'defective' and subsequently replaced.

However, if no one considers the actual damage to the ESP (other than a few professionals here in the forum), then such damage will never be detected.

And that's why there are very few descriptions available about the effects of specific types of damage or wear on the ESP (Electrostatic Precipitator).

I've spent a ridiculous amount of time searching worldwide for descriptions of damage and wear on the ESP VP37, and even asked about it here, but I found nothing!

The way workshops handle ESP (Electronic Stability Program) issues would be translated to the car itself, meaning:

Ashtray full and tank empty? => Vehicle no longer functions? => Replacement of the vehicle is necessary.

It would be great if I'm wrong and someone actually writes something.

@donalexo

As you describe it, it sounds like you might have at least one faulty pressure equalization valve on your VP37. As far as I can tell, they are directly screwed to the outlets of the individual refrigerant injection lines. Therefore, to replace them, you wouldn't need to interfere with the internal workings of the ESP. Have you looked into what they cost?
A decrease in one of the pressure relief valves should be most noticeable at low speeds, as the time between injections is longer, allowing more pressure to escape from the injection lines. This means that the idling control system would suffer the most in this situation. Am I correct?

best regards
Jan.

Hello Jan03!

Yes, I completely agree with you on all points!

The exchange shouldn't be a problem (provided you can easily remove the copper gaskets) from the pump housing ). A valve costs, in my opinion, about 30 EUR, so that's about 120 EUR for a set !

As you correctly pointed out, the effect should be most pronounced at idle speed, and ideally at a high fuel temperature.
Based on the readings for the idle speed control, I can see that the values are around +/- 0.2 mg/H when the engine is cold. However, after the engine has been run properly, the values drop to +0.8 mg/H on two cylinders. This is accompanied by an audible knocking sound coming from one or two cylinders.

Ich frage mich nun, ob es die Düsen oder die Gleichdruckventile sind! Who has advice?

Regards,
Alex.

Hello everyone.

Here's a humble question from a semi-professional.

What is meant by the term 'equal pressure valves'?
What check valves are being referred to here?

These devices are actually called 'pressure relief valves.'

They are located between the pump and the injection line and have the task of assisting in pressure reduction within the injection line at the end of the injection stroke. This is necessary because, otherwise, the injectors may not close properly and could drip or spray excessively.

There are various types of valves, including pressure-reducing valves and valves with flow-limiting features.

The task is always to extract a defined volume of fluid from the line at the end of the injection process in order to quickly and safely close the injection valve. Furthermore, the pressure in the lines should be maintained at the same level between injection cycles to ensure consistent conditions.
However, the pressure in the pipeline shouldn't be reduced too much, otherwise it could cause cavitation damage.

CU Gremlin.

donalexo wrote:

Based on the readings for the idle speed control, I can see that the values are around +/- 0.2 mg/H when the engine is cold. However, after the engine has been properly run, the values drop to +0.8 mg/H on two cylinders. This is accompanied by an audible knocking sound coming from one or two cylinders. I am now wondering whether it is the nozzles or the pressure relief valves! Who knows the answer?

Hi Alex,

If no one comes up with anything more insightful:
"Why don't you swap the exhaust valves between a 'strong' cylinder and a 'weak' cylinder?"
If the indicator lights for the idle speed control system move along with the valves, then the problem is likely with the valves themselves.

ulf wrote:

Try swapping the exhaust valves between a "strong" cylinder and a "weak" cylinder.

Hello fellow enthusiasts,

hoho, that's a real pain, especially when the old seals don't want to come out and the new ones keep falling off and disappearing .

It's an interesting theory... I know, sometimes I'm hard to convince, but I would also expect piston damage to be more likely caused by faulty pressure valves than by nozzles with high mileage .

Okay, so if the weather starts getting warmer again, I will definitely replace the valves. I can still afford the 120 euros, especially after having already replaced the nozzles for 480 euros, and that didn't necessarily guarantee success.
@Haehnlein:
I'll put a cloth underneath, just to be on the safe side. It helps with fishing .

best regards
Jan.

Hi!

If I consider what you've written here, it seems I'm starting to understand the causes of the difference in volume between the cylinders!

I'm experiencing the same problem as described by Dalexo.
When it's cold, the readings are below zero. But when it's warm, the readings suddenly become positive.
I was also able to identify the misfire on cylinders 3 and 6.
I thought it might possibly be a valve problem, or that carbon deposits had built up.
But it hasn't disappeared yet, even after using a descaling agent.
In addition to that: there's a slight clicking sound after releasing the accelerator.

Is this the only reason for the difference in quantity, or are there other factors involved?
(As Michael already described: the camshaft has seized...) hopefully not .


cu: Marko


Engine: AKE, 132 kW, V6 TDI.
Mileage: 143,000 km