Cribus
New member
In case it helps anyone else, I finally seem to have got rid of this smell that would come and go at random. Turns out it was coming from the fuel vapour segregator, which lives in the gap between the nearside rear inner and outer wings.
As standard, pipes from the two valves on the top of the fuel tank take fuel vapour to the segregator (and release tank pressure). From the segregator another pipe takes the vapour away, it goes down through the floor next to the tank and makes its way to the charcoal canister situated under the bonnet, beneath the coolant reservoir (on my 96 car anyway). After trying many other things which included sealing off the charcoal canister and running the vapour exit pipe to atmosphere beneath the rear end of the car (after reading that the canister can be the source of the smell, which it turned out not to be in my case), I finally sealed off and isolated the segregator so the vapour now goes straight from the tank to atmosphere at the rear underside of the car. And the fuel smell in the cabin and boot is finally gone.
So in other words, what happens now is that the two pipes which take fuel vapour from the valves on the top of the tank now go to a T-piece and a third pipe then leads from that down through the floor to the rear of the car where the vapour exits. The original pipes going to and from the segregator are now sealed so that the unit is isolated and does nothing.
What confused me in the beginning was that the smell would usually be present when the car had been parked, and when you started up and drove off the smell would go. But if you then opened a window, the smell would return which made me think that it must be coming from the front of the car, presumably under the bonnet somewhere. But what I think was happening was that when you opened a window the incoming wind would create pressure in the rear of the cabin which would draw out the fuel smell from the tank area behind the seats and bulkhead. Now the smell doesn't appear no matter how much gale blows in from the windows.
I hope that helps some of you who have the smell. There seem to be many possible causes though, I went through other checks and changes before finding this cure for my car. I appreciate that having the fuel vapour exiting to atmosphere isn't ideal, but you really can't smell it even if you crouch down towards the underside of the boot where the vapour leaves the pipe so the amounts involved can't be that great. Whether this setup would be noticed and frowned upon by an MOT man I don't know (luckily we don't have MOT's over here in the IOM). But I wouldn't think that a thin black rubber pipe zip-tied to the boot floor would be likely to catch anyone's eye.
Biggest pain was getting the rear bulkhead out. Undo the screws, grasp the nearside end of the bulkhead at top and bottom and pull it towards the front of the car, especially at the bottom, until you can slide it out of the driver's door. That's after removing the bits of black plastic trim etc at the sides of the bulkhead that are in the way. To create the new vapour pipe circuit behind the bulkhead all I bought was some black fuel pipe (6mm inner diameter to push on to the exiting blue pipes which I snipped) and the plastic T-piece. Since finishing the job I've filled the tank (never done that before!) and checked that the tank is being vented properly by removing the cap every so often to check for pressure hisses, and all is fine. Runs perfectly and no smell.
As standard, pipes from the two valves on the top of the fuel tank take fuel vapour to the segregator (and release tank pressure). From the segregator another pipe takes the vapour away, it goes down through the floor next to the tank and makes its way to the charcoal canister situated under the bonnet, beneath the coolant reservoir (on my 96 car anyway). After trying many other things which included sealing off the charcoal canister and running the vapour exit pipe to atmosphere beneath the rear end of the car (after reading that the canister can be the source of the smell, which it turned out not to be in my case), I finally sealed off and isolated the segregator so the vapour now goes straight from the tank to atmosphere at the rear underside of the car. And the fuel smell in the cabin and boot is finally gone.
So in other words, what happens now is that the two pipes which take fuel vapour from the valves on the top of the tank now go to a T-piece and a third pipe then leads from that down through the floor to the rear of the car where the vapour exits. The original pipes going to and from the segregator are now sealed so that the unit is isolated and does nothing.
What confused me in the beginning was that the smell would usually be present when the car had been parked, and when you started up and drove off the smell would go. But if you then opened a window, the smell would return which made me think that it must be coming from the front of the car, presumably under the bonnet somewhere. But what I think was happening was that when you opened a window the incoming wind would create pressure in the rear of the cabin which would draw out the fuel smell from the tank area behind the seats and bulkhead. Now the smell doesn't appear no matter how much gale blows in from the windows.
I hope that helps some of you who have the smell. There seem to be many possible causes though, I went through other checks and changes before finding this cure for my car. I appreciate that having the fuel vapour exiting to atmosphere isn't ideal, but you really can't smell it even if you crouch down towards the underside of the boot where the vapour leaves the pipe so the amounts involved can't be that great. Whether this setup would be noticed and frowned upon by an MOT man I don't know (luckily we don't have MOT's over here in the IOM). But I wouldn't think that a thin black rubber pipe zip-tied to the boot floor would be likely to catch anyone's eye.
Biggest pain was getting the rear bulkhead out. Undo the screws, grasp the nearside end of the bulkhead at top and bottom and pull it towards the front of the car, especially at the bottom, until you can slide it out of the driver's door. That's after removing the bits of black plastic trim etc at the sides of the bulkhead that are in the way. To create the new vapour pipe circuit behind the bulkhead all I bought was some black fuel pipe (6mm inner diameter to push on to the exiting blue pipes which I snipped) and the plastic T-piece. Since finishing the job I've filled the tank (never done that before!) and checked that the tank is being vented properly by removing the cap every so often to check for pressure hisses, and all is fine. Runs perfectly and no smell.