Air bubbles in diesel fuel, faulty fuel tank?

Hi,

In my Octavia 1.9TDI (81kW, 160,000 km, 95% RME), I have noticed a significant loss of power.

To be able to conduct a reasonable diagnosis, I first...
He tried to remove the air from the diesel line and followed the advice from the technical articles.
Even when he was new, there was a sense of potential, but not as much as there is now.

So far, unsuccessful:
- Open the fuel filler cap.
- new fuel filter,
- Replace hose clamps.
- Seal the hose connection between the filter and the pump using Dirko sealant.

The air bubbles only appear in the pipe between the filter and the pump. There are no air bubbles between the pump and the filter (checked with a clear hose).

After the fuel tank system was dismantled, the following was discovered:
A valve is located in the line leading to the filter. It opens when there is approximately 1 bar of overpressure (or vacuum, from the pump's perspective) in the direction of the filter, and it blocks flow in the opposite direction.

The return flow from the filter ends openly in the tank.

I assume that the valve in the tank is failing due to the strong vacuum inside.
The fault lies with the management. The air bubbles are simply a result of excessive negative pressure.
The reason for the performance loss could possibly be a lack of internal pump pressure.

my questions:
Has anyone else noticed something similar on their fuel tank?
Could the valve be swollen due to RME?
What's the downside of removing (drilling out) the valve?

Thank you.
Viktor.

I don't quite understand what you're planning.

1. You have air between the ESP and the filter.
-> There are two lines, and both have air in them, but only one of them does. Which one?

Why are you expanding the tank if there are no air bubbles?

m;

Hello,

'I have air in the fuel line between the fuel filter and the injection pump.'
In the fuel line leading to the fuel injection pump. I can't say whether there's air in the return line, and in my opinion, it's also irrelevant.

2. I didn't remove the entire fuel tank, but only the plastic part that includes the fuel level sensor and the two fittings. One of these fittings is connected to the hose that goes to the fuel filter, and the other is connected to the return line from the fuel filter.

http://homes.hallertau.net/~karell/tank.gif

What I'm trying to find out is whether it's normal to need to create a vacuum of at least 1 bar in order to draw fuel from the tank.

That is to say: Is it worth removing the (possibly swollen) valve in the tank inlet fitting, or is it originally designed that way?

Hi,
Viktor.

Are you sure that the thermostatic valve on the filter is sealing properly?

I encountered this problem with a part from a colleague at ASV. Subsequently, he either purchased a different (newer) retaining clip from VW or fabricated one himself.

After that, there was no room for anything else.

Unfortunately, I can't say anything about the printing.

m;

Viktor wrote:

What I'm trying to find out is whether it's normal to need to create a vacuum of at least 1 bar in order to draw fuel from the tank.

It's not possible to go above 1 bar anyway...

It's probably a check valve; it should open easily. Is there a replacement part available for it? It's definitely not installed there for no reason.

Hello,

My new 1Z also has air in the hose. Filters and ESP.
He is clearly drawing air bubbles through. I suspect the cause is the check valve on the filter. When I press on it firmly, the bubbles slowly disappear from the hose. If I stop using it for a while, it doesn't take long for the pimples to reappear.

Does the valve need to be completely replaced now? Or is the problem due to the seal on the diesel filter? Should both be replaced? The filter has only been installed for 3 months.

Can this small amount of air cause performance losses?
The old 1Z took 8.3 seconds in the DZR with 185/65r14 tires, while the new one takes a very long time, 9.5 seconds.
It's important to note that the older model has a GSHD (Ground Source Heat Distribution) system, while the new one doesn't, but it does have manual climate control. The new one revs up better, and without stopping, you wouldn't think it's slower; in fact, it feels quite the opposite.

The air shouldn't be there.

I've also noticed that my 1Z pulls worse when the tank is empty (okay, I always drive it until it's almost empty - but it's still drivable .
I recently filled up the tank of my Variant with 70 liters of fuel.

The problem with the thermocouple is that it's only held in place by this silly clamp, which can't really apply any pressure to the seal. Maybe using two seals would help???

Regarding your 1Z comparisons, it would probably be interesting to know more about the cars themselves.
- Motor Control Unit (MCU) numbers.
- Mileage
- The '96 model should have ABS -> Weight.
- furthermore, he has painted bumpers -> weight
- What are the LMM (likely maximum mass) values for the two vehicles?
etc...

My 1Z Variant (shorter transmission than the standard Golf, 1400 kg curb weight) achieves 9.2 seconds (without) or 7.8 seconds (with 10 Ct) in the DZT (drag strip) test, using 185 60 14 winter tires.
I haven't tried those 195 60 14 summer sandals yet.

Hi,

Okay, I'll see if I can find something to put underneath. The air doesn't belong there, that's right .

The STG numbers should be identical for both cars, and the mileage should also be approximately the same (one with 186,000 km, the other with 179,000 km). Both have new magnetic valves, fuel filters, and timing belts.
Both are 1996 models with three doors. The newer one has air conditioning and ABS in addition, while the older one only has basic equipment and no ABS. But an ABS system isn't that difficult to use. To achieve the measured values, I would have to be over 50kg heavier with the new one.

I can post the LMM values for the new system, but I have nothing left from the old one.

A log of groups 8, 9, and 11 during the trip: Download

A log of groups 10, 2, and 6 during the trip: Download

A log of groups 7, 10, and 4 is available for download.

I extracted the groups from a technical article about finding performance bottlenecks. It's possible that the logs are a bit disorganized, but it's usually difficult to analyze them on your own. I hope you can find something useful. I haven't found any errors myself.

Oh yeah, I also remembered that the speedometer in the new one is quite inaccurate. The speedometer in the old Golf was extremely accurate. By the way, according to GPS, with 195/50 R15 tires, I'm going exactly 50 mph at 2000 rpm. It's possible that the tachometer isn't displaying the correct value, or at least that's what I suspect, since the speedometer also has such a large deviation. The AGR seems to be "defective" on the new one.[/url]

Approximately, how large is the air bubble in the diesel pre-supply line?

@ x

Great, you also have AFib, so we can compare notes and experiences.

Yours seems to grip the road better when starting from a standstill than mine does. But he also has other target values!! ???

I have a deviation of -3.1° (relative to the target), and I'm off by 0.4°, but the "basic settings" are perfectly aligned with the ideal line.

TAKE A LOOK AT THIS GERMAN LABEL FILE

http://people.freenet.de/golf-schrauber/028-906-021.lbl


In logs 8, 9, and 11, it can be observed that the EDC (presumably a vehicle or object) frequently approaches the Russian border.

I have the same issue, but as far as I know, it shouldn't be happening.

A8 = F8 - MIN(D8:F

(Group 8: Time, RPM, Driver Request, Torque Limiting, Russ Limiting)

Boost pressure looks good.

m

Hello Viktor,

'I had the same problem with air bubbles between the filter and the ESP a few years ago. At the time, I started using biodiesel. After a few thousand kilometers, the biodiesel cleaned all the fuel lines of diesel deposits, and the filter became clogged. I then installed a new filter, and the problem was solved, but you could still see small air bubbles in the line. After that, people from VW told me many terrible stories.' Of course, biodiesel was to blame for everything, blah blah blah...

Turns out, I accidentally damaged the valve on the filter; there's a crack on the edge. This crack, which was barely visible to the naked eye, was enough to allow a minimal amount of air to pass through.
Get a new valve and sealing ring; it doesn't cost a lot, but it will give you peace of mind.

My advice on biodiesel:

Based on my long-standing experience (I will be posting more details soon), I strongly advise you to stop using biodiesel, if it's not too late.
I used biodiesel myself for 5 years, sometimes mixed with regular diesel, sometimes 100% biodiesel, and only regular diesel in the winter (due to better starting performance). Until recently, I was even promoting biodiesel. And now, my ESP (Electronic Stability Program) has also failed. I noticed it in time by the smell of diesel, and at the next gas station, I filled up with biodiesel. The swelling effect of RME has sealed the ESP again, for almost a year now, but for how long???

I'm already saving up for a sealant for my ESP (Electronic Stability Program).
If you use biodiesel, you should factor in the cost of a new ESP (Electronic Stability Program)!!! Is it still worth it?

dieselmartin wrote:

Great, you also have AFib, so we can compare notes and experiences.

yes

Quote:

Yours seems to grip the road better when starting from a standstill than mine does. But he also has other target values!! ???

"Other target values? I have always used the target values for the start of injection as listed in the table here on the forum." According to this table, the injection timing should be well within the tolerance range.

Quote:

In logs 8, 9, and 11, it can be observed that the EDC (presumably a vehicle or object) frequently approaches the Russian border. I have the same issue, but as far as I know, it shouldn't be happening. A8 = F8 - MIN(D8:F (Group 8: Time, RPM, Driver Request, Torque Limiting, Russ Limiting)

Um, what does the Russian border tell me? I can't seem to find any technical articles that explain it. Soot line = A boundary where soot would be present?
According to my father, the car isn't smoking, or at least, it wasn't smoking enough for him to notice.

Quote:

Boost pressure looks good.

Well, it's a little bit below the target, but acceptable. The older 1Z engine produced slightly more power, but the turbo was constantly making a whooshing sound. Also, the new engine doesn't have any turbo lag, which the older one did. Probably because the AGR valve is defective in the new one.

So, it seems the LMM (likely referring to a lambda sensor or similar) is indeed detecting something if I'm interpreting your statement about soot reduction correctly. But I still find the difference between the two cars to be significant in terms of DZR (likely referring to a specific performance metric). Possibly, the air inside the filter is actually the problem.
Ah yes, the old 1Z engine sounded completely different. It was louder in tone, had a more distinct "nailing" sound, and people didn't like to rev it up too much because of that. The new one just hums, and you can't hear the hammering as clearly.

"Russgrenze" refers to the amount of fuel injection that the EDC (Engine Control Unit) would allow for the car without causing it to produce black smoke (soot).

Normally, it should never be reached, as it will always be the minimum of the three values.
Driver request, torque limit, and Russian border injected.

Is Russ the Min, could the car do more, you want more too, but you don't get it .

The threshold is quite low, as evidenced by the 10-cent tuning, where the amount is artificially increased without the EDC (Electronic Data Capture) system detecting it, and yet nothing works!

You can get rid of that turbo hole with just 10 cents, it's amazing .

m;

Sure, I still have an Authal Box here .
But the new one doesn't have that turbo lag. It revs up very smoothly. Maintaining a constant speed in the fourth gear on the highway, all the way to the redline, without any loss of power.

So, according to the logs, everything seems to be okay in your opinion? I didn't find anything there either.
But somewhere, there has to be a loss of power. Let's see what pressing the valve will do.

@viktor

I once experienced something similar. The diesel fuel only flowed for 2 minutes from the tank, and then the engine shut off and wouldn't restart. It only started again after about half an hour. The reason was a valve inside the tank that closes at a certain angle to prevent fuel from leaking in case of an overturn. In my case, this valve was blocked. So, the fuel line is usually located near the tank opening, and you can use compressed air to clear it. After that, the valve should be free again. By the way, you can also use this method to bleed your fuel lines. It was an Audi 80 B4 with a 1Z engine.

Best regards.

thomas

@ x

I haven't looked at all the logs.

Okay, let's create a mass flow rate graph for the DZT; it will also clearly show how the LMM is performing.

Here is my translation:
[img][/img]

The green lines indicate that the air mass drops significantly starting at 3000 RPM.
I've been thinking about getting a new LLM, just because it's so nicely cheap .

Or I can simply wear out the old one until it's unusable, then I WILL have to buy a new one .

mhttp://www.luxus-wg.de/~martin/auto_bilder/dzr_lmm.gif{MARKER}