Fuel smell, vent tanks and valves
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- itchyfeet
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Fuel smell, vent tanks and valves
the poptop has had a fuel smell since I had it, it's much worse in summer, in winter it's ok, I have replaced the filler neck and the hoses to the tanks but what I didn't realise until recently is there is a float valve in the top of each tank.
I took the tanks off today and found that I can blow and suck through the pipe to the valve so it's venting ( I assume if there was liquid in the tank it would close), there should be a valve on the end of the pipe too part number 321201890 but they are both missing, one can be seen split and sitting on the tank on the last picture.
These are described as gravity valves so I assume they stop venting normally.
I ordered some replacements but does anybody know if this is enough to cause a fuel smell?
thanks
P1080973 by Paul_Barr, on Flickr
P1080995 by Paul_Barr, on Flickr
I took the tanks off today and found that I can blow and suck through the pipe to the valve so it's venting ( I assume if there was liquid in the tank it would close), there should be a valve on the end of the pipe too part number 321201890 but they are both missing, one can be seen split and sitting on the tank on the last picture.
These are described as gravity valves so I assume they stop venting normally.
I ordered some replacements but does anybody know if this is enough to cause a fuel smell?
thanks
P1080973 by Paul_Barr, on Flickr
P1080995 by Paul_Barr, on Flickr
- tonytech
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Re: Fuel smell, vent tanks and valves
The tanks in the wheel arches are "expansion tanks" designed to cope with the U shaped main fuel tank. I believe the valve on the top seal if the van turns over,
The ears on the end of the pipes often get lost, their main task is to stop dirt getting into the system. I dont think they are valves. (on USA models with stricter emmissions, they vent into the intake system)
The usual reason for fuel smells is degraded fuel lines (modern fuel rots old rubber lines) or a rusted tank... dirt and water get trapped on the top...
The ears on the end of the pipes often get lost, their main task is to stop dirt getting into the system. I dont think they are valves. (on USA models with stricter emmissions, they vent into the intake system)
The usual reason for fuel smells is degraded fuel lines (modern fuel rots old rubber lines) or a rusted tank... dirt and water get trapped on the top...
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- 937carrera
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Re: Fuel smell, vent tanks and valves
I assume you've read this
http://forum.club8090.co.uk/viewtopic.php?f=37&t=162534
If you want to check the operation of the float valve I think you might need to remove it from the overflow tank and move it manually I'm thinking the valve should be normally closed, and only open when the float opens the valve. (otherwise there would be permanent fuel evaporation)
http://forum.club8090.co.uk/viewtopic.php?f=37&t=162534
If you want to check the operation of the float valve I think you might need to remove it from the overflow tank and move it manually I'm thinking the valve should be normally closed, and only open when the float opens the valve. (otherwise there would be permanent fuel evaporation)
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- itchyfeet
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Re: Fuel smell, vent tanks and valves
937carrera wrote:I assume you've read this
http://forum.club8090.co.uk/viewtopic.php?f=37&t=162534
If you want to check the operation of the float valve I think you might need to remove it from the overflow tank and move it manually I'm thinking the valve should be normally closed, and only open when the float opens the valve. (otherwise there would be permanent fuel evaporation)
thanks
thats my question, are you sure of the answer?
- 937carrera
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Re: Fuel smell, vent tanks and valves
Not certain of the answer, sorry, but if it was the other way round then fuel would vent to atmosphere when parked up and the only purpose of the valve then would be to stop fuel exiting down the pipe when cornering.
The reason I looked at my pipes was because a) I couldn't fill the tank without leaking, b) I parked the van up on the right hand side of the reserve line, when I next went to start it the level was almost down to the left side of reserve. Missing / deteriorated /disconnected pipes being the cause.
You have two to test / corroborate / break as you remove them
The reason I looked at my pipes was because a) I couldn't fill the tank without leaking, b) I parked the van up on the right hand side of the reserve line, when I next went to start it the level was almost down to the left side of reserve. Missing / deteriorated /disconnected pipes being the cause.
You have two to test / corroborate / break as you remove them
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
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- bigherb
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Re: Fuel smell, vent tanks and valves
The valves only close when inverted to stop fuel leaking if you roll over, otherwise they vent both ways to let pressure out when the fuel expands due to ambient temperature changes/hot fuel returning from the engine and to stop a vacuum when the fuel is used. There isn't a valve on the end of the breather it is just a moulding to stop the pipe ends sitting on the top of the tank and getting blocked.itchyfeet wrote: I took the tanks off today and found that I can blow and suck through the pipe to the valve so it's venting ( I assume if there was liquid in the tank it would close), there should be a valve on the end of the pipe too part number 321201890 but they are both missing, one can be seen split and sitting on the tank on the last picture.
These are described as gravity valves so I assume they stop venting normally.
I ordered some replacements but does anybody know if this is enough to cause a fuel smell?
thanks
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- 937carrera
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Re: Fuel smell, vent tanks and valves
Good to know - I hadn't considered putting a T25 on its roof
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
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- itchyfeet
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Re: Fuel smell, vent tanks and valves
VW T25 rotation by Paul_Barr, on Flickr
what I don't really understand is why a vent pipe cracked or perished should be any worse thatn the fumes coming out of these pipes unless its petrol sloshing around coming out of perished pipes further down.
what I don't really understand is why a vent pipe cracked or perished should be any worse thatn the fumes coming out of these pipes unless its petrol sloshing around coming out of perished pipes further down.
- Jim San
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Re: Fuel smell, vent tanks and valves
There's a certain dodgeyness about the hub cap in the top pic
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- 937carrera
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Re: Fuel smell, vent tanks and valves
Nice picture - should make repairing the sills easier
You're right, of course, except from a design perspective the assumption is that the pipes from the tank to the overflow tank are assumed to be in good condition, so the valve is only needed as a safety feature in an accident when the vehicle is inverted and fuel could flow out of the vents, similar to electric fuel cut off valves on carbs cutting off the supply. I'm actually kicking myself a bit for not thinking about this - I had heard about it before.
I'm not sure that this information helps with your original fuel smell issue, is it worth checking that the 4 pipes to the tank are still connected and the fuel lines are not weeping ?
You're right, of course, except from a design perspective the assumption is that the pipes from the tank to the overflow tank are assumed to be in good condition, so the valve is only needed as a safety feature in an accident when the vehicle is inverted and fuel could flow out of the vents, similar to electric fuel cut off valves on carbs cutting off the supply. I'm actually kicking myself a bit for not thinking about this - I had heard about it before.
I'm not sure that this information helps with your original fuel smell issue, is it worth checking that the 4 pipes to the tank are still connected and the fuel lines are not weeping ?
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine
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- 937carrera
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Re: Fuel smell, vent tanks and valves
Jim San wrote:There's a certain dodgeyness about the hub cap in the top pic
I see what you mean
In the second pic I can also see the missing trombone, cracked as usual which is why it has fallen off
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine
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- itchyfeet
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Re: Fuel smell, vent tanks and valves
Jim San wrote:There's a certain dodgeyness about the hub cap in the top pic
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Re: Fuel smell, vent tanks and valves
Brings a whole new meaning to "hanging out in the VW scene"
Mind you, who wouldn't get excited playing with expansion tanks.
Mind you, who wouldn't get excited playing with expansion tanks.
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- itchyfeet
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Re: Fuel smell, vent tanks and valves
Is it possible to change the inner breather rubber pipes without dropping the tank?
the one to the balance pipe looks accessible (16 on link ) but not sure about the one to the rear vent pipe.( 15 on link)
there don't appear to be any clips
http://www.realoem.me/Volkswagen/RDW/T2 ... /201/32000" onclick="window.open(this.href);return false;
the one to the balance pipe looks accessible (16 on link ) but not sure about the one to the rear vent pipe.( 15 on link)
there don't appear to be any clips
http://www.realoem.me/Volkswagen/RDW/T2 ... /201/32000" onclick="window.open(this.href);return false;
- 937carrera
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Re: Fuel smell, vent tanks and valves
It "is" possible, and by the looks of things many people on here have done it.
When I did it I was on a ramp and dropped the tank completely down as I wanted to inspect the top anyway. You need height to get the supporting bars clear and out of the way. I prefitted hoses "15" to the metal pipe, plastic connector and the hose again (with a little extra length) and similarly "16" to the grommets "6". You should therefore remove the grommets from the tank before dropping it on mine the cross pipe "1" is secured to the underside of the chassis with a P clip type arrangement. That isn't shown on the picture. With everything assembled you then have to force the grommets back into the tank. I used a bit of WD40 to lubricate and it's awkward to get the force at arms length.
If you aren't going to drop the tank then I would say it is certainly possible, but it's fiddly reaching through the chassis even with the wheel removed to get the hoses in position. One of those jobs that is much easier once you have done it. Have a swear box handy if you like
When I did it I was on a ramp and dropped the tank completely down as I wanted to inspect the top anyway. You need height to get the supporting bars clear and out of the way. I prefitted hoses "15" to the metal pipe, plastic connector and the hose again (with a little extra length) and similarly "16" to the grommets "6". You should therefore remove the grommets from the tank before dropping it on mine the cross pipe "1" is secured to the underside of the chassis with a P clip type arrangement. That isn't shown on the picture. With everything assembled you then have to force the grommets back into the tank. I used a bit of WD40 to lubricate and it's awkward to get the force at arms length.
If you aren't going to drop the tank then I would say it is certainly possible, but it's fiddly reaching through the chassis even with the wheel removed to get the hoses in position. One of those jobs that is much easier once you have done it. Have a swear box handy if you like
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine