Fuel Tank Pressurising
Discussion
Hi,
Iam after some advice regarding what I think is a problem with the carbon can system.
After Ive been driving the Griff for a while the fuel tank starts making the usual boinging noise, but its also now started to pressurise the fuel tank to an extent that I can hear air hissing out of the fuel cap once I switch off. Releasing the cap releases a rush of air/vapour from the tank.
One thought is that the flow from the petrol return from the fuel rail may be pressurising the tank if there is no breather i.e. the carbon canister system isnt working. Would this sound sensible?
In August I finished rebuilding most of the front of the car and part of the rebuild/refurb included renewal of all the petrol lines including the breather from the tank to the carbon canister...a bit of a co-incidence? Possibly not. Maybe Ive trapped or flattened the line from the breather to the carbon canister. Something to definately check.
However, if it turns out not to be this, then is there an easy fix such as replacing the cabon canister itself? Its probably 11 years old and will have done over 50,000 miles.
Can I just leave the breather pipe un-connected to the canister in the front wing?
If I get rid of the carbon can system will the ecu spit its dummy out if it cant get a signal from the electrical connection to the canister?
If I can get rid of it without any subsequently developing electrical issues/fault codes then I would be happy to do so.
I would be grateful for advice and other peoples experiences with this black magic and witchcraft. Thanks.
Marty
Iam after some advice regarding what I think is a problem with the carbon can system.
After Ive been driving the Griff for a while the fuel tank starts making the usual boinging noise, but its also now started to pressurise the fuel tank to an extent that I can hear air hissing out of the fuel cap once I switch off. Releasing the cap releases a rush of air/vapour from the tank.
One thought is that the flow from the petrol return from the fuel rail may be pressurising the tank if there is no breather i.e. the carbon canister system isnt working. Would this sound sensible?
In August I finished rebuilding most of the front of the car and part of the rebuild/refurb included renewal of all the petrol lines including the breather from the tank to the carbon canister...a bit of a co-incidence? Possibly not. Maybe Ive trapped or flattened the line from the breather to the carbon canister. Something to definately check.
However, if it turns out not to be this, then is there an easy fix such as replacing the cabon canister itself? Its probably 11 years old and will have done over 50,000 miles.
Can I just leave the breather pipe un-connected to the canister in the front wing?
If I get rid of the carbon can system will the ecu spit its dummy out if it cant get a signal from the electrical connection to the canister?
If I can get rid of it without any subsequently developing electrical issues/fault codes then I would be happy to do so.
I would be grateful for advice and other peoples experiences with this black magic and witchcraft. Thanks.
Marty
I can't answer your question but can add some information which may or may not help you..
My fuel tank suffers the same problem, this usually occurs when starting a hot engine and is usually accompanied by noises from the fuel pump which sounds to me like it may be scavenging for fuel.
To try and cure it I removed the carbon canister blocking off the tube that went to the plenum and leaving the tube from the tank to vent to the atmosphere. This did not make any difference at all, the tank and fuel pump noises still occur. Removal of the canister has resulted in the emission of strong fuel vapours from the vent tube but only when re-starting a hot engine.
My next plan was to check the operation of the roll-over valve which I believe is located somewhere near the fuel filler.
My fuel tank suffers the same problem, this usually occurs when starting a hot engine and is usually accompanied by noises from the fuel pump which sounds to me like it may be scavenging for fuel.
To try and cure it I removed the carbon canister blocking off the tube that went to the plenum and leaving the tube from the tank to vent to the atmosphere. This did not make any difference at all, the tank and fuel pump noises still occur. Removal of the canister has resulted in the emission of strong fuel vapours from the vent tube but only when re-starting a hot engine.
My next plan was to check the operation of the roll-over valve which I believe is located somewhere near the fuel filler.
DarkMatter said:
My next plan was to check the operation of the roll-over valve which I believe is located somewhere near the fuel filler.
Mine sits just behind the tank by the fuel filler. If you remove the filler cap, can you blow down the tube that used to go to the carbon canister ?. Would check if the tube is blocked or the rollover valve.I've just done some testing.
With the fuel filler cap off I blew into the vent tube which used to connect the carbon canister to the fuel tank - there was some resistance, but not a great amount - I then sucked through the tube, again there was a little resistance but also I detected a slight 'rasping' noise from the fuel tank area.
I repeated the above with the fuel filler cap on - this time there was noticeably more resistance - when I sucked through the tube the 'rasping' noise from the fuel tank area was much louder, in fact it was the exact noise which I'd misdiagnosed as being the fuel pump scavenging. Following this test I removed the fuel filler cap and there was a bang from the fuel tank and a rush of air out of the fuel filler.
This appears to confirm that the fuel tank is being pressurised - maybe this is due to a fault in the roll-over valve, or maybe it has been connected the wrong way round? I cannot see any marks on the valve to show which way it should go but it is orientated such that the pipe from the fuel tank enters the valve at the bottom and the vent/carbon canister pipe connects to the top. The top of the valve can be identified by the fact that the diameter of the valve decreases in three or four steps.
With the fuel filler cap off I blew into the vent tube which used to connect the carbon canister to the fuel tank - there was some resistance, but not a great amount - I then sucked through the tube, again there was a little resistance but also I detected a slight 'rasping' noise from the fuel tank area.
I repeated the above with the fuel filler cap on - this time there was noticeably more resistance - when I sucked through the tube the 'rasping' noise from the fuel tank area was much louder, in fact it was the exact noise which I'd misdiagnosed as being the fuel pump scavenging. Following this test I removed the fuel filler cap and there was a bang from the fuel tank and a rush of air out of the fuel filler.
This appears to confirm that the fuel tank is being pressurised - maybe this is due to a fault in the roll-over valve, or maybe it has been connected the wrong way round? I cannot see any marks on the valve to show which way it should go but it is orientated such that the pipe from the fuel tank enters the valve at the bottom and the vent/carbon canister pipe connects to the top. The top of the valve can be identified by the fact that the diameter of the valve decreases in three or four steps.
DarkMatter said:
I've just done some testing.
With the fuel filler cap off I blew into the vent tube which used to connect the carbon canister to the fuel tank - there was some resistance, but not a great amount - I then sucked through the tube, again there was a little resistance but also I detected a slight 'rasping' noise from the fuel tank area.
I repeated the above with the fuel filler cap on - this time there was noticeably more resistance - when I sucked through the tube the 'rasping' noise from the fuel tank area was much louder, in fact it was the exact noise which I'd misdiagnosed as being the fuel pump scavenging. Following this test I removed the fuel filler cap and there was a bang from the fuel tank and a rush of air out of the fuel filler.
This appears to confirm that the fuel tank is being pressurised - maybe this is due to a fault in the roll-over valve, or maybe it has been connected the wrong way round? I cannot see any marks on the valve to show which way it should go but it is orientated such that the pipe from the fuel tank enters the valve at the bottom and the vent/carbon canister pipe connects to the top. The top of the valve can be identified by the fact that the diameter of the valve decreases in three or four steps.
Ive found that Vodka has the same effect but doesnt leave a petrol aftertasteWith the fuel filler cap off I blew into the vent tube which used to connect the carbon canister to the fuel tank - there was some resistance, but not a great amount - I then sucked through the tube, again there was a little resistance but also I detected a slight 'rasping' noise from the fuel tank area.
I repeated the above with the fuel filler cap on - this time there was noticeably more resistance - when I sucked through the tube the 'rasping' noise from the fuel tank area was much louder, in fact it was the exact noise which I'd misdiagnosed as being the fuel pump scavenging. Following this test I removed the fuel filler cap and there was a bang from the fuel tank and a rush of air out of the fuel filler.
This appears to confirm that the fuel tank is being pressurised - maybe this is due to a fault in the roll-over valve, or maybe it has been connected the wrong way round? I cannot see any marks on the valve to show which way it should go but it is orientated such that the pipe from the fuel tank enters the valve at the bottom and the vent/carbon canister pipe connects to the top. The top of the valve can be identified by the fact that the diameter of the valve decreases in three or four steps.
Ive since graduated from Superplus to brake cleaner - its great with ice
Thanks for the info DM. The roll over valve is also something I'll have a look at. I would hope I never have to trust this if the car did actually go over though as it seems to be somewhat agricultural.
Cheers
Marty
rev-erend said:
Check the owners manual - I seem to remember reading that the filler cap needs to be in the middle position and not fully tightened home.
Hi,I checked through my owners manual but couldnt find a reference to this. Ive since had the car out on a couple of trips and although the petrol cap hissing isnt there (or at least I cant hear it), the tank is still doing very good bass drum impressions.
Ive also tried replacing the cap but not rotating it fully home to see if it makes a difference, but the musical tank still plays on.
Car is in garages at the moment...
Checked roll-over valve, and apparently is fine.
I have Emerald on mine, and the garage is wondering whether the carbon canister valve has been rigged up to the Emerald - if not, the valve probably won't be allowing the tank to vent, and this may be the source of my pressurising.
My car is rather different from most peeps however, so my gut feel is that this might not help anyone else
Dom
Checked roll-over valve, and apparently is fine.
I have Emerald on mine, and the garage is wondering whether the carbon canister valve has been rigged up to the Emerald - if not, the valve probably won't be allowing the tank to vent, and this may be the source of my pressurising.
My car is rather different from most peeps however, so my gut feel is that this might not help anyone else
Dom
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