Tank Vent-Ventilation

Hello!

Next funny question:

My T4, manufactured in 2001, 2.5 TDI ACV,
has been sitting unused in my workshop for quite some time.
The tank is quite empty, and the warning light was already on.
So, I picked up a canister of diesel today and filled up the T4.

"There was something strange about it, I thought the fuel cap was broken because it wouldn't close properly."
"Applying a bit more pressure then helped,"
but to my dismay, a powerful pressure equalization occurred immediately.
I am so shocked that I couldn't even watch it.
I think, however, there was a vacuum in the tank.
But neatly.

Otherwise, I don't really have any problems with the car.

Should I do anything about that,
or could it be
that the vacuum was formed due to the temperature differences?
It's possible that I took the car to the garage once when the outside temperature was around 20°C, and now it's around 12°C.

Does anyone know how the fuel tank ventilation works, specifically with the use of solenoid valves when the ignition is switched on?

As far as I know, it's a valve in the tank lid.

Hi!

Looks like work for me.
So, the fuel cap doesn't have a vent, even though it looks like it does.
The told me that, and I also tried it myself.

My investigation has revealed that there is a vent, which is located next to the tank filler. The valve or the vent hose is the problem. I think it's best to let the master handle it. has said that they have already replaced many complete tanks because it is directly connected to the tank, so it is a part of the tank.

Well, so far so good, I'll see about removing the seats, and try to achieve something through the opening in the floor pan, towards the fuel sender.
Otherwise, the tank will probably have to be lowered, or completely removed.

I will report.

The are exaggerating, but
The vent hose is located near the brake line, simply tap on it. Often, dirt will fall out, or you can push the hose and blow through it with compressed air (but use very little pressure). The best way is to open the fuel tank cap so that the pressure can be released.

Or, drill a small hole in the lid, which can cause dripping when turning right with a full tank.

In my rice cooker, there is also a strong vacuum that builds up, which strongly sucks the lid of the pot when it is almost empty. Problem or not?

Fuel supply is running, fuel pressure is within the expected range (measured). The fuel tank lid does not have its own ventilation; I did not see anything on the tank itself. Perhaps at the inlet? Then it would also have to be sealed.

I haven't driven a gasoline engine in a long time. The previous diesel I drove never developed any noticeable vacuum.

Was about the fuel tank ventilation system having to run through a filter, because the emissions of hydrocarbons (HC) also need to be limited from the fuel?

I mean, even with the first plastic tanks, the plastic itself would allow too much HC to pass through, so that the coated plastics needed to remain compliant.

In this regard, a simple tank venting system is unlikely to be sufficient.

A beautiful story, about which I'm not sure if it's an 'urban legend', is about troubleshooting a Mercedes 600 that was supposed to reach a maximum speed of 120 km/h. After the engine and gearbox replacement, the clogged fuel tank vent was discovered.

Quote:

The fuel tank must be vented through a filter

Furthermore, the uncle reveals that the diesel engine doesn't produce this (HC emission) and therefore doesn't require a filter.

The Benzier, on the other hand, has exactly this filter.

Since TDI is being suppressed here, the following applies: there is no filter

At least, that's how I see it

Hello
m;

Hello!

Okay, here's a progress report, and it's a good one:

I haven't been able to find the described venting hose with the rubber bell, even after a long search.

So, therefore, I removed the seats earlier today, and also the handbrake lever, and folded down the floor mat, so that I could access the cap in the floor pan, which is located above the fuel gauge.

According to the image that showed me, the tank-mounted vent valve is located a few centimeters to the left and next to it.
I could feel this through the open lid, and the vent funnel was therefore directly in the fitting on the tank.
Meaningfully, also with the opening facing forward, so that all the road dirt can be nicely sucked in.

The hose, which is normally intended for that purpose, has apparently been misused as a fuel line for a retrofitted auxiliary heater.
They put it together using a T-piece.

Okay, so, the hose is attached to the vent, and I'm blowing into it.
Just managed to get through with thick cheeks. Produced the typical valve squeak.
Open the fuel tank cap, fill the hose with brake cleaner, let it sit for a while, then blow it out, repeat the same process with compressed air a couple of times.
Okay, it looks good now.
One can almost blow into the tank without any resistance.
But sucking it out doesn't work.

I will test it again tomorrow, and rinse it a few more times.
but I think the problem has been found and fixed.

Maybe I'll also attach an original-style vent hose, if I can manage to get one through.