Welcome to 911UK
The only place for Porsche, 911uk is the definitive enthusiast and resource site for the Porsche 911.
Registration is fast, simple and absolutely free, so join up today for full access to the site and benefit from latest member offers.

Porsche Classifieds
Sell Your Porsche on 911uk
Create a Free Classified Advert
Search Ads
Classified Adverts FAQ
Trade Classified Information
Buyer & Seller Fraud Protection
Consumer Rights Act
Pre Purchase Inspection (PPI)
Porsche Car Sourcing
Porsche Cars Wanted
Official Porsche Centre Reviews
Model
Stock
Porsche 911
992 : 2019- 1
991 : 2011-2019 0
997 : 2004-2012 0
996 : 1997-2005 31
993 : 1993-1998 5
964 : 1989-1993 2
Carrera 3.2 : 1983-1989 3
Carrera SC : 1977-1983 1
930 Turbo : 1975-1989 0
Early 911 : 1964-1977 0
Porsche Other Models
Classic : 1950-1965 0
Boxster : 1997- 22
Cayman : 2005- 13
Cayenne : 2003- 2
Macan : 2014- 2
Panamera : 2009- 1
912-914-924-928-944-968 1
959 - CarreraGT - RaceCar 0
Car Parts For Sale & Wanted
Other Items For Sale & Wanted
Wheels Tyres For Sale & Wanted
Number Plates For Sale Wanted

Porsche Services
Porsche Body Shop Repair
Paint Protection & Wrapping
Porsche Classic Insurance
Porsche Classic Parts
Porsche Classic Restoration
Porsche Design Collection
Porsche Engine Gearbox Rebuild
Porsche Heritage & History
Porsche News
Porsche Picture Gallery
Win a New Porsche 911

Porsche Parts
Body Parts, Body Styling
Brakes, Clearance
Electrical, Exhausts
Engine Cooling, Engine Electrical
Engine Rebuild, Heating Cooling
Interior Incar, Lighting
Rubber Seals, Service Parts
Steering, Suspension
Transmission, Workshop Tools
Early 911, 911 - 930, 928 - 968
964 - 993, 996 - 997, Boxster
Cayman, Cayenne, Panamera

Porsche Model Range
911 [992] 2018-Current
Porsche 911 [992]
911 [991] 2011-2019
Porsche 911 [991]
911 [997] 2004-2012
Porsche 911 [997]
911 [GT] GT1-GT2-GT3
Porsche 911 [GT]
911 [996] 1997-2005
Porsche 911 [996]
911 [993] 1993-1998
Porsche 911 [993]
911 [RS] RS-RSR
Porsche 911 [RS]
911 [964] 1989-1993
Porsche 911 [964]
911 3.2 1983-1989
Porsche 911 3.2 Carrera
911 SC 1977-1983
Porsche 911 SC
911 [Early] 1964-1977
Porsche 911 [Early]
Boxster & Cayman
Porsche Boxster & Cayman
Cayenne & Panamera
Porsche Cayenne & Panamera

911uk Site Partners

Post new topic   Reply to topic
Author Message
infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8326
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Sun Jan 06, 2019 9:40 pm    Post subject: Reply with quote

I think I have a spare fuel cap somewhere anyway so this is no issue, will order the vac gauge and update later in the week.
_________________
http://euroroadtripper.blogspot.co.uk/

 
  
View user's profile Send private message Visit poster's website
   
infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8326
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Tue Jan 08, 2019 5:22 pm    Post subject: Reply with quote

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.



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.



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.





The diaphragm seals against the centre hole.



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

It was obviously full of carbon particles.



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.



I'm not sure this helps us understand this system much more but at least we can now see what is inside.
_________________
http://euroroadtripper.blogspot.co.uk/

 
  
View user's profile Send private message Visit poster's website
   
Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16527
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Tue Jan 08, 2019 5:49 pm    Post subject: Reply with quote

I always thought there was going to be a big footprint in there Confused Grin
_________________
2000 Manual 996 C4 Arctic Silver Convertible


 
  
View user's profile Send private message
   
kurlykris
Indianapolis


Joined: 30 Jun 2014
Posts: 2489
Location: Warwickshire


PostPosted: Tue Jan 08, 2019 5:59 pm    Post subject: Reply with quote

How did all that gravel get in there Question Get Me Coat
_________________
1998 996.1 C2 3.4 with "Aerokit Cup"
2006 Boxster S sport chrono
2010 Mercedes E350 AMG Sport

 
  
View user's profile Send private message
   
deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6987
Location: Brighton


PostPosted: Tue Jan 08, 2019 7:46 pm    Post subject: Reply with quote

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 .
_________________
.

My Daughter's Crowdfunding has hit the target see Here

Thank you all so Very much .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
View user's profile Send private message
   
infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8326
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Tue Jan 08, 2019 9:06 pm    Post subject: Reply with quote

deMort wrote:
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 .


Funny you should say that, when I was drilling the fuel cap a spring came out of it, (which I thought was strange) I wiggled the inner and outer of the cap and it does seem to be in two parts, although the movement was very minimal. Question


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


I don't think anyone would worry about spending money on parts from your advice, the cost of any labour they would incur would soon outweigh that.
_________________
http://euroroadtripper.blogspot.co.uk/

 
  
View user's profile Send private message Visit poster's website
   
Mac996t
Nürburgring


Joined: 26 Mar 2011
Posts: 494


2004 Porsche 996 Turbo

PostPosted: Wed Jan 09, 2019 1:33 am    Post subject: Reply with quote

The gray valve you’ve dis assembled, that reveals a lot. In your previous posts you say this valve only flows in the direction of the arrow allowing air to flow from the tank to the canister but not letting anything flow in the other direction.

Looking at your pics it looks to me like there actually is a route for air to go in the opposite direction. I think this is what the two groups of four small holes are for. They allow a small flow in the other direction by lifting the small orange diaphragms. If you blow through the valve it may seem like it’s only one way because in one direction (from tank to canister) it flows a lot quite easily. I bet if you blow in the other direction there will be a flow but only a small one, not much but enough to equalise the pressure in the tank as the fuel level slowly drops!!!

I think this is the answer to the mystery of how the pressure is equalised as the fuel level drops

Also looking at the design of the valve it will flow in the direction of the arrow when there’s more pressure in the tank than in the canister allowing vapours the flow to the canister eg on a hot day when the fuel tank heats up.

What's not so obvious is that if there’s a vacuum applied to the canister the valve will shut and prevent this vacuum from reaching the fuel tank even though that flow would be in the direction of the arrow too, so in this respect it behaves differently to a normal one way valve.

What do you reckon any of this make sense?!!

Mac
 
  
View user's profile Send private message
   
infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8326
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Wed Jan 09, 2019 4:09 am    Post subject: Reply with quote

I think that is the missing piece of the jigsaw. The small holes must let air back the other way back to the tank. The 2 x 4 holes did have little diaphragms on them but I couldn't work that out at the time because they got damaged when I cut it apart but what you have said makes sense now.

So deMort is correct that this is the route the air must take. I will try to do a diagram later of how it flows. It must pull the air from the open ended pipe at the top of the Canister but as it has to go through the large foam filter and carbon particles it doesn't draw any air unless it does actually need it and the two bottom pipes that go from tank to engine have little restriction between them so that is the easiest direction of flow until the vacuum takes over.

Fingers crossed when the new valve/ pipe arrives and is fitted that it cures this. I'll still attach the vac gauge to see what is happening though.

That arrow has been a red herring all along, I don't see the point in that being there Mad
_________________
http://euroroadtripper.blogspot.co.uk/



Last edited by infrasilver on Fri Jan 18, 2019 9:58 pm; edited 1 time in total
 
  
View user's profile Send private message Visit poster's website
   
infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8326
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Tue Jan 15, 2019 6:20 pm    Post subject: Reply with quote

I set my rig up that deMort suggested, using a vac/pressure gauge connected to an old fuel filler cap and sealed to act like a normal cap would by sealing the filler tube.





I had the gauge taped to the windscreen so that I could see what was happening while driving.

I also set my Gopro up as I couldn't look 100% of the time while driving.



I covered 40 miles on all kinds of roads, motorway, dual carriageway and local roads. I also used around 10 litres of fuel so this would have made a decent space in the tank to have to fill with air again.

Unfortunately after all this set up, the gauge didn't move at all during the whole 40 mile journey. I think this is a good thing and hopefully suggests everything is working as it should?

I will monitor the fuel cap when opening it to see if air is sucked in at all, this will only show up on a long run though.
_________________
http://euroroadtripper.blogspot.co.uk/



Last edited by infrasilver on Tue Jan 15, 2019 9:10 pm; edited 1 time in total
 
  
View user's profile Send private message Visit poster's website
   
911munKy
Montreal


Joined: 26 Nov 2014
Posts: 528



PostPosted: Tue Jan 15, 2019 8:52 pm    Post subject: Reply with quote

“the gauge did move at all”

should that be Didn’t?

Sounds like good news after a challenging journey, congratulations.
_________________
2000 C2 996
 
  
View user's profile Send private message
   
infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8326
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Tue Jan 15, 2019 9:11 pm    Post subject: Reply with quote

911munKy wrote:
“the gauge did move at all”

should that be Didn’t?

Sounds like good news after a challenging journey, congratulations.


Edited to say "didnt move"

Yes, hopefully good news
_________________
http://euroroadtripper.blogspot.co.uk/

 
  
View user's profile Send private message Visit poster's website
   
deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6987
Location: Brighton


PostPosted: Fri Jan 18, 2019 9:51 pm    Post subject: Reply with quote

Sorry for the delay .. not been very well this week so not been online since Monday ..

Just make sure the fuel cap / vacuum gauge is properly sealed .. other than that you seem to have no vacuum buildup and hence you dont have a fault anymore.
_________________
.

My Daughter's Crowdfunding has hit the target see Here

Thank you all so Very much .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
View user's profile Send private message
   
infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8326
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Fri Jan 18, 2019 9:56 pm    Post subject: Reply with quote

deMort wrote:
Sorry for the delay .. not been very well this week so not been online since Monday ..

Just make sure the fuel cap / vacuum gauge is properly sealed .. other than that you seem to have no vacuum buildup and hence you dont have a fault anymore.


No problem at all kind sir.

I made sure the seal on the cap was tight and the pipe to the gauge was too.

I did half expect to see the gauge move in either direction, sucking or blowing when the valve opened either way but it didn't budge so hopefully that is the end of it? Need to take it out for a long run at some point soon just to confirm.

Get well soon.
_________________
http://euroroadtripper.blogspot.co.uk/

 
  
View user's profile Send private message Visit poster's website
   
deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6987
Location: Brighton


PostPosted: Fri Jan 18, 2019 10:02 pm    Post subject: Reply with quote

logically there should be no vacuum buildup hence the gauge would remain at zero...

Considering just how strong the fuel tank is then i would guess at a negative 5 bar or more to collapse one ..

I did a conversion to a vacuum for this .. it made no sense to me ! so i stuck with negative bar .. you know what i mean Smile
_________________
.

My Daughter's Crowdfunding has hit the target see Here

Thank you all so Very much .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
View user's profile Send private message
   
infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8326
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Fri Apr 05, 2019 12:26 am    Post subject: Reply with quote

I'm just coming back to this tread as I had a gauge issue that I think is cured now but when I was at it I found out some info that may be of use.

I noticed a while ago when I filled up the gauge was very slow to rise and I thought there may be a problem in the tank, it took about an hour to get to a true reading of what fuel was in the tank, the next time I filled up it was fine. It wasn't until I had a run over to Whitby that my fuel light came on with 30 miles range and and I filled up with fuel that the gauge didn't move upwards at all and just kept going down to zero, I knew I had around £60 worth of fuel in so I just drove home knowing I had enough.

I stripped the battery and battery tray off to get to the top of the tank and sender unit, I had thoughts of the tank being collapsed again but when I pulled everything out the tank was fine and I started to swap parts over from my other fuel senders, I used a cleaner actuator arm and refitted everything. Nothing was binding so I think it was just a bad reading. I refitted and have filled up twice since, both times getting a true reading.

Now this is the reason I am updating, I found the 3.6 cars do actually have a fuel filter and I also know the reason when the tank collapses the sender fails at the same time other than just the stand bending.

This is the fuel sender scale and after switching an old one over, as I thought this may be my gauge problem and after installing I found out it didn't work and then realised why, there was a hairline crack in the board and any time the tank collapses it'll damage this as its very brittle a little like ceramic.



When I removed another one it fell to pieces, it was already broken in it mounting. I refit the one that was already fitted.



I also decided to change the fuel pressure regulator as I suspected it may be this causing some running issues, this didn't make any difference to the running but this does show you how to replace it if you ever need to.



And I also found whilst stripping the sender unit down a fuel filter, I'm not sure if it available separately but this is good news if you are chasing a fuelling problem. This one looked fine and with the screen filter at the base of the pump I suspect they don't get dirty very often.

I can easily be got to in less than an hour.



I did eventually changed the whole float assembly as the one fitted that connects the sender scale was a little dirty and I think this did cure the dodgy gauge, or at least I hope it has?
_________________
http://euroroadtripper.blogspot.co.uk/

 
  
View user's profile Send private message Visit poster's website
   
cdmci
Newbie


Joined: 26 Dec 2009
Posts: 14



PostPosted: Fri Apr 05, 2019 12:07 pm    Post subject: Reply with quote

In this type of application you can't have any more than 1bar pressure differential. Even if you pump a hard vacuum in the tank it is the external air pressure that collapses the structure - ie no more than 1 bar. So if the tank did collapse because of a pressure differential it is not as strong as you might think. 1bar is still a good deal of force when you look at the psi x area...
 
  
View user's profile Send private message
   
deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6987
Location: Brighton


PostPosted: Fri Apr 05, 2019 7:07 pm    Post subject: Reply with quote

Can i just say .. neither i nor anyone else at work had any idea there was actually a filter inside of the unit .. i very much doubt its available as a seperate part due to not even us knowing there is one there but thank you ..

i've learnt something new today Smile
_________________
.

My Daughter's Crowdfunding has hit the target see Here

Thank you all so Very much .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
View user's profile Send private message
   
infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8326
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Fri Apr 05, 2019 11:10 pm    Post subject: Reply with quote

The post was mainly for you as I knew you would be interested.

I assume it is available somewhere and I will update with a part as soon as I find a number or ID of some kind. The pump screen protects it to some extent but as with all filters they will get dirty and most pumps probably have a screen before they get to the main fuel filter so it may be also of use to others chasing a problem.
_________________
http://euroroadtripper.blogspot.co.uk/

 
  
View user's profile Send private message Visit poster's website
   
deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6987
Location: Brighton


PostPosted: Sun Apr 07, 2019 4:20 pm    Post subject: Reply with quote

Thank you .. i have to say i've studied all the pictures in this thread ... we never split things apart these days i'm afraid .. its all replace the unit even though i could often fix things .. did it for many years pre Porsche days.

Bit of info re carbon canister ..

I changed one on a 986 the other week , the new canister is modified , it doesn't Have the top pipe , vent to atmosphere one .. it seems to have an inbuilt vent in the same place .. it also feels different inside .. when i tap it i can feel springs vibrating at the base .. some sort of internal valve i guess ..

Its also the standard 987 part .. they have just stopped making the 996 ones and use the 987 ones instead .. cost cutting .

The valve on the filler neck . it doesn't fully shut when the filler cap is removed , you can still blow through it but with a much greater resistance than when the fuel cap is fitted pressing on the switch , cant remember if you already said that though Smile
_________________
.

My Daughter's Crowdfunding has hit the target see Here

Thank you all so Very much .



Mechanic

7pm - 9pm

Now At An Indy.
 



canister 2.jpg
 Description:
 Filesize:  118.79 KB
 Viewed:  789 Time(s)

canister 2.jpg



canister 1.jpg
 Description:
 Filesize:  61.45 KB
 Viewed:  789 Time(s)

canister 1.jpg


  
View user's profile Send private message
   
infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8326
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Tue Apr 16, 2019 12:59 pm    Post subject: Reply with quote

Well it seems this saga is not yet over, I was out enjoying the car around the Peaks on Sunday but when a mile from home the car conked out, I'd ran out of fuel with 80 mile range left. Got a lift to get fuel and it fired up and drove on.

I'll admit I did think the gauge was actually reading truer than it has for a while but it seems not, I was getting decent MPG similar to before the tank problems and the amount I put in seemed to show correctly on the gauge although I didn't make a note of exactly how much I put in.

I haven't taken the sender out again yet and I also was wondering if there was a calibration procedure for the C2 tanks, I know we have said not but I can't work out why the gauge is reading wrong still. The tank does seem to be venting fine and there are no problems with the tank misshaping again.

I have been really careful to make sure I haven't had anything bind the float when installing the sender and I checked the float assembly to make sure it is not damaged or bent by comparing it to the other two floats I have.

I'm thinking of using the tank capacity of 64L (Googled capacity but also saw 76L but I think incorrect) and putting in increments of 16L, 32L and 48L of fuel to measure the gauge is reading 1/4, 1/2 and 3/4 of a tank correctly but other than that I can't think of a more accurate test?
The petrol station is about 1/4 mile away, if I put 2 or 3 litre of fuel in it to get there then put in the required amount, obviously I need to drain the tank fully first.
_________________
http://euroroadtripper.blogspot.co.uk/

 
  
View user's profile Send private message Visit poster's website
   
Display posts from previous:   
Post new topic   Reply to topic   All times are GMT - 12 Hours
Goto page Previous  1, 2, 3, 4, 5, 6, 7  Next
Page 6 of 7

 
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You can attach files in this forum
You can download files in this forum
You cannot post calendar events in this forum