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Cedric · Joined: 27 Aug 2004 Posts: 2818 Location: Sweden

Hi guys.

I have a serious problem, my car (the 931) pisses out fuel out of the vent line on the right in left corners. The tank has been down this winter, cleaned, painted and changed all hoses etc. Didnt do any difference. This only happens when I got lots of fuel in the tank. Its obvious that the small vent line cant vent the pressure out without pushing the fuel out.

What should i do, mount a tiny catch tank ? Why doesnt it work, is it maybe the little plastic valve. It seemed to work ok when I had it out..

My friend with a 924 ´76 has the same problem..
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1980 924 Turbo
www.instagram.com/garagecedric/

Rich H · Posted: Thu Jul 15, 2010 7:04 am Post subject:

I'd use a catch tank to be certain then a vent line from that.
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

Ozzie · Posted: Thu Jul 15, 2010 8:34 am Post subject:

Isnt there supposed to be a plastic tank up in the C pillar?
might want to check your hoses and tank routing.
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
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Cedric · Joined: 27 Aug 2004 Posts: 2818 Location: Sweden

No theres no plastic tank on the early models, ive looked in a later 924 (83) and it hade the uppdated setup, with the more squary box on the c pillar, seems like porsche also was aware of this ...My hope are that a small catch tank could separate the gases and fuel. What I dont hope for is for the catch tank to be filled up and the same problem continues.

My first thougths was to have 3 connections, one from the small vent line, one in the top that goes out into the air via the rest of the vent line and the third a return line connected to the thicker tube at the filling. But I dont think that will work since fuel is all the way up to the filler cap in the corners and thus fill fill upp the catch tank instead, maybe if a small valve is put in between so fuel only can go one way. Probably impossible to understand without pictures

And the us cars shurely have totally different solutions, but I start to get really worried since more track days are coming in august..
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1980 924 Turbo
www.instagram.com/garagecedric/

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

mount a one way valve...?
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Rich H · Posted: Thu Jul 15, 2010 6:47 pm Post subject:

Or fir a 'roll over' valve, that will pass air but not fuel.
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

Cedric · Joined: 27 Aug 2004 Posts: 2818 Location: Sweden

Rich H · Posted: Fri Jul 16, 2010 2:28 am Post subject:

It has a float in it that blocks the valve.
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

Cedric · Joined: 27 Aug 2004 Posts: 2818 Location: Sweden

Cedric · Joined: 27 Aug 2004 Posts: 2818 Location: Sweden

Just so this problem gets a solution:

I bought the following valve slightly in panic since I had a track day coming up:
http://www.merlinmotorsport.co.uk/p3555/ROLL-OVER-VALVE-1/4-IN-LINE/product_info.html

Its a valve with both steel ball and floating ball, so I removed the oem roll over valve and installed this. No more fuel passing out the vents and also with no pressure in the tank. Sucess !
_________________
1980 924 Turbo
www.instagram.com/garagecedric/

924RACR · Posted: Wed Aug 11, 2010 9:56 pm Post subject:

Thanks for the info.

My tank vent used to be blocked; we'd always have excess pressure in the tank after a race session.

We just pulled the tank after the last race, to fix a crack, and I cut the vent line free from the stock plumbing to allow it to vent successfully.

But I guess we won't have this dumping problem, since we never run a full tank... Well, unless we ever run an enduro!

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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Cedric · Joined: 27 Aug 2004 Posts: 2818 Location: Sweden

And I must always start the day with full tank, or else I have to fill up between the sessions:). 30 l / 100km is a bit problematic consumption wise

_________________
1980 924 Turbo
www.instagram.com/garagecedric/

924RACR · Posted: Thu Aug 12, 2010 9:39 pm Post subject:

I think you'll find that if do put the fuel back in after each session, the car will be much more consistent!

These cars are very sensitive to fuel load, as the tank is directly over the rear axle. When you try to balance the car for handling, burning off even as little as 1.5 gal will make a noticeable difference in the balance. That's all of 15 minutes racing for us.

So, to counter this, we always start out with exactly the same fuel level.

As the car burns off gas, it oversteers more and more.

You really ought to do the same.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Nobbi · Joined: 24 Aug 2006 Posts: 1398 Location: Germany

The problem can be the use of a Volkswagen Golf(Rabbit) 1 fuel cap.
The VW has no vent holes! The original Porsche cap has some.
Easy fix if you know.

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NA 924 - april/1977- 4-speed-audi gearbox.
500.000 km with fun.....and new toy:Porsche 944 S2 Cabriolet.Other car Daimler c-class cabby,brandnew..Plus : DEUTZ 4005 tractor Built 1967

Cedric · Joined: 27 Aug 2004 Posts: 2818 Location: Sweden