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Broken down, cut out. Fuel tank collapsed, bent sender

deMort, not to contradict you but rather to try to add to your post, I thought the carbon canister was to filter vapour venting to atmosphere rather than air entering the tank?
For example when the tank is half empty, on a hot day the vapour will expand and increase the pressure in the tank. The vent valve and canister allow the vapour to vent to atmosphere but the carbon reduces the HC in the vented vapour.
Perhaps the vent/canister works in both directions?
Or I may be wrong!
 
Griffter you are more than welcome to contradict me any time you want :) i certainly dont know everything .. all i can ever do is give my opinion the same as everyone else .

i dont know the system 100 % but have figured most of it out and to be honest i was trying to bump this thread and get a few more comments so that perhaps we can figure out whats causeing the tank collapse .. Infrasilver has modified a pipe atm ...

So in my eyes we still havent got to the bottom of this .. and i would like to .

The carbon canister is indeed there to catch fuel vapours .. one for save the planet but mainly its a dam waste of a burnable fuel to just dump it.

Its just a canister with activated carbon granules as far as im aware .. fuel vapour will be collected in these granuals and when needed be drawn into the engine.

The part i was struggleing with is that dam pipe thats open to atmosphere .. you would think that this pipe would stop a tank collapse but the diaphram pipe had been replaced and thats the only part i can see that would block ANY air getting into the tank other than removeing the filler cap ...

yet it still collapsed .. this and Locosaki post above yours .. his was similar and the vent valve on the engine was causeing it makes me think that although this pipe is open perhaps it cant give the volumn of air to the tank that is needed .

As fuel is pumped out of the tank then air has to replace it from somewhere .

It may be a combination of this pipe and the valve on the engine that does it .. either way those are the bits that need checking .. we dont have a blockage but a restriction i feel .

Couple of images .. one is the american system but that is different to ours .. we have no pressure sensor or shut off valve ..

The other is the canister internals .. again we have no shut off valve there.
 

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Sorry for the slow response the last couple of days, we have had pet death at home so I haven't been in the garage at all to even look at the hesitancy or this EVAP system again.

The thing we really need to establish is how air gets back into the tank and there are only two ways it can as far as I'm aware, the first being the tank vent pipe running from the bleeder valve on the filler tube to the bottom of the canister and the filler pipe bleeder valve itself. The vent valve is one way only so cannot get air into the tank, only take air away, like when you are filling the tank with fuel. The bleeder valve can be the only other way?

The purge valve at the engine again only takes fuel vapour from the tank/carbon canister to burn. Anything past the carbon canister cannot return air back to the tank due to the factory vent valve.

This is why I'm using an old pipe where the diaphragm has broken, allowing air to pass both ways, just to relieve the vacuum when the tank is getting empty. This should let air back into the tank through the carbon canister from the pipe open to atmosphere that exits under the gearbox. I'm still not sure what part the open pipe plays in this system, its just an open pipe from the top of the carbon canister??

Its all not correct and how it was designed but seems to be holding the tank together but won't get it thorough an MOT, I just swap the pipe over at MOT time as I did a few weeks ago.

But as you do deMort, I would like to fathom out what the problem is.
 
Chris .. i am truly sorry for your loss .. it is heart breaking .

Ill not continue this until you have moved on .

I have a theory but it goes against what you think so its best if we give it a bit of time untill you are ready .

Once again .. i am truly sorry .
 
My condolences Chris, dreading the day I lose my 4 legged best mate.


On a side note, I reckon it's deffo a fuel delivery issue.
 
Fair enough young man.

Imho you have several faults atm , when you get the durametric hooked up then i can try and work through things with you .

For now the tank fault ..

Image below that i have edited ..

My opinion .. No.7 is called a Vacuum limiting valve .. so thats what it does .. i dont feel its a one way valve but i think its a vacuum valve that opens when there is excessive vacuum build up in the tank .. this will then allow air to enter ther tank either from the canister pipe that vents to atmosphere or the engine purge valve .. or perhaps even both .

Also think of just how much vacuum it would take to colapse a fuel tank .. that plastic is harder than steel .. its designed to withstand a serious car crash .

There are no other pipes on the tank or filler tube .. so the diagram we have is it .

There is nothing in the fuel filler cap that has a vent , its not like a coolant cap which can release with pressure as far as im aware anyways ... the cap seals the filler tube .

If it was me .. i would replace no.7 with a brand new pipe , i would check that valve on the filler neck .. which as far as im aware is there to help fill the car up with fuel .. it allows air to escape the tank whilst fuel goes in ...

There is a lever under the fuel cap so that when the cap is removed it opens this valve .

I would check the pipes covered by the circles for any blockage .

You have a work around atm but im not happy with this .. i doubt you are either .. my concern is that the car is running lean .. because this is on the tank venting side the car will not adapt to this ( no adaption whilst venting ) .. a lean running engine can cause valve issues over a long period .. they burn out basically due to excess heat on a lean burn .

have a read and see what you think as at the end of the day this is just my assumption .. but also please bare in mind .. the only 2 times i have herd of this fault have both been due to no.7 .


I wish i did know how every part on every Porsche works and indeed how every system works .. but im afraid theres not a person in the world that knows that .. we just try and work things out as we go .
 

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deMort said:
My opinion .. No.7 is called a Vacuum limiting valve .. so thats what it does .. i dont feel its a one way valve but i think its a vacuum valve that opens when there is excessive vacuum build up in the tank .. this will then allow air to enter ther tank either from the canister pipe that vents to atmosphere or the engine purge valve .. or perhaps even both .

Also think of just how much vacuum it would take to colapse a fuel tank .. that plastic is harder than steel .. its designed to withstand a serious car crash .

If it was me .. i would replace no.7 with a brand new pipe

I agree, if that does indeed flow air back to the tank to release the vacuum it will be the thing to change next, the clue is in the name :roll:

This valve on the pipe does have an arrow moulded into it pointing away from the tank which usually shows the direction of flow on most cars parts I have seen before and does test only one way but I suppose that depends what pressure it can take in either direction.

I was previously amazed when the tank collapsed that the vent pipe from the tank managed to survive from being collapsed along with the tank. They are very stiff plastic but so is the tank.

I have also traced and checked all the pipework to make sure they are not kinked or blocked so this should be fine.
 
My concern .. and i mean huge here .. we replace these bits but have no way of checking if it has actually solved the fault .

I certainly dont want to be wrong here .

Another collapsed tank doesnt bear thinking about so a bit of a bodge but something i think i would be doing in this case ..

I have a vacuum / pressure gauge .. a cheap one from Mac tools .. you just fit a rubber pipe to it and plug it into what ever you want to measure ..

I would drill a hole in the fuel cap .. fit the pipe / gauge along with plenty of silicone to seal it .. fuel flap open and the gauge taped to the flap along with tapeing the flap to the wing.

I would then drive the car 20 miles to make sure there is no vacuum build up showing on the gauge ..

A bodge but it should show if there is still a fault .

A fuel filler cap is cheap .. a tank isnt .
 
So while I am waiting for parts to arrive and the Vacuum gauge I got busy breaking stuff.

I found an old fuel cap so drilled that through in readiness for the Vac gauge to be bonded in place.

31723455427_7953d66699_c.jpg


The next thing to get attacked was the vent valve pipe. I cut both ends off it to reveal what is inside without damaging the internals so I can closely inspect it.

The arrow I have previously mentioned showing direction away from the tank.

46612564642_c43d098fcd_c.jpg


Now I have split this valve I can't really see how it lets air back into the tank, although the tiny holes may be able to do this as they go between both sides. I understand the US pipe is called the Vacuum Limiting Valve but here in the UK it is called a Vent Pipe.

Air being pushed from the tank lifts the diaphragm to release it into the Carbon Canister. If air was being drawn through it or there was any vacuum from the tank I can only see that it would create a tighter seal on the diaphragm not letting any air back to the tank.

31723452327_9a151b6c79_c.jpg


46665064081_51567f00de_c.jpg


The diaphragm seals against the centre hole.

46612555442_79ebd4e305_c.jpg


And while I had the hacksaw out I cut the Carbon Canister to reveal what was inside.

It was obviously full of carbon particles.

46612551502_3a6b6a5f2c_c.jpg


The filter screen at the bottom goes to the fuel tank and the second one at the bottom goes to the engine purge valve. there is a foam filter at the base for this pipe. The top also has a large foam filter and this pipe exits to the open ended pipe under the gearbox.

32790320718_c9515e0997_c.jpg


I'm not sure this helps us understand this system much more but at least we can now see what is inside.
 
I always thought there was going to be a big footprint in there :? :grin:
 
How did all that gravel get in there :?: :coat:
 
Thats facinateing to actually see inside these items .. ive never cut either appart so have only refered to the Porsche images till now .

Im not really any the wiser on how this valve works .. the small holes .. i dont see the point of them if its just a one way valve ( thats not normal ) but im afraid at the end of the day im going with my usual logic ..

I can see no other way of air entering the tank other than via no.7 .

If the fuel cap had some sort of pressure release then it would be that .. but it doesnt and the fuel filler tube is sealed by the fuel cap .

Im afraid i can only go with what i would do .. replace no.7 and fit a vacuum gauge so that it can be monitored.

Sometimes i do sit here and realise .. im telling you guys to do this and replace that .. i am in effect spending your money ..

Sometimes i sit here thinking i dont really know the system .. im working on what i would do or what i can work out and perhaps it would be better if i just didnt say anything .. dont get involved so to speak ..

I dont like to do that .. i will try to help even if like this thread .. im not totally sure of how the system works but i know it needs to be fixed so im doing what i can .

It still worrys me though .
 

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