Page 1 of 2 12 LastLast
Results 1 to 10 of 12

Thread: Vacuum in fuel tank.

  1. #1
    Join Date
    Oct 2007
    Location
    Williamstown, Victoria
    Posts
    573

    Vacuum in fuel tank.

    I have noticed for a while now a strong vaccum in the fuel tank when I take the fuel cap off.
    You can hear the pressure change as the fuel cap is being undone.
    Is this normal, or is there a problem with my fuel cap causing a fuel tank venting blockage?
    Any thoughts appreciated!
    Cheers, Pete.

  2. #2
    Join Date
    Apr 2009
    Location
    Crafers West South Australia
    Posts
    10,332
    Are you quite certain its vacuum, not pressure escaping? Warm weather means there will be a modest vapour pressure build up, that's what the cap is for. If in doubt, get a new cap. It is a universal style that should be available anywhere, to suit all major makes with screw in petrol caps.

  3. #3
    Join Date
    Sep 2012
    Location
    Perth Australia
    Posts
    282
    Mine is the same, be like it forever, it's a 2001 Bosch

  4. #4
    Join Date
    Jan 1970
    Location
    Avoca Beach
    Posts
    10,604
    The venting of the fuel tank is via a solenoid valve into the inlet manifold under certain conditions eg overrun at over 1500RPM.
    If you are driving on a hot day on flat ground and stop for fuel you can get quite a pressure build up if you stop for fuel.
    Don't worry be happy as it is completely normal.

    Regards Philip A

  5. #5
    Join Date
    Oct 2007
    Location
    Williamstown, Victoria
    Posts
    573
    Definitely a vacuum, there is no fuel smell when I open the cap. I would imagine if it was a pressure build up, there would be fuel smell as the pressure was released from the tank.
    I can not feel any escaping pressure with my hand either.
    Mine is a 2001 Thor as well, interesting yours does it as well Hammer H, might be a quirk of our model.
    I've never had any issues from it, but it did have me wondering if it was normal.
    Thanks for the replies!
    Cheers, Pete.

  6. #6
    Join Date
    Apr 2009
    Location
    Crafers West South Australia
    Posts
    10,332
    All the (working) caps I've met have a small valve in the centre of the cap facing the tank. Let the fumes dissipate from your cap and suck gently on the valve protrusion. It should take little effort to get the valve to open in the direction of into the tank. If not, try a new cap and compare. Pressure holding is higher and you shouldn't be able to easily blow through the cap valve. Some people block the valve as they can smell petrol vapour as they pass the car, this is not the best thing to do. Caps wear out and should be thrown away if no longer working properly.

  7. #7
    Join Date
    Feb 2013
    Location
    Gosford, NSW, Australia
    Posts
    2,412
    I too have that faint petrol smell around the filler area as well, though my tank definitely holds pressure

    It seems the Tridon Non Locking Fuel Cap TFNL227 is a direct fit, so I may try one of those and see if it improves things

    Steve
    MY96 4.6 HSE P38. Niagara Grey; "The Phoenix"
    MY99 4.6 HSE P38. LPG, Blenheim Sliver; "Voldemort" burnt to a cinder
    MY79 RR Classic, Gone, MY57 Series 1 SWB, Long gone
    P38 write ups and info on my website http://p38.hts.com.au/

  8. #8
    Join Date
    Oct 2007
    Location
    Williamstown, Victoria
    Posts
    573
    An update, I got an aftermarket fuel cap, put it on, went for a drive, opened the cap and guess what?
    It's doing exactly the same thing.
    Oh well, it's not causing any issues, I'll just live with it!
    Cheers, Pete.

  9. #9
    Join Date
    Feb 2010
    Location
    Townsville, QLD
    Posts
    2,474
    Mine does the vacuum thing too mate, even on long trips driving from full to empty without stopping. Itís never caused an issue or fuel surge for me, and likewise Iíve not worried about it.

    Cheers
    Keithy

    Green 2000 P38 Range Rover HSE - Gone
    Blue 1999 P38 Range Rover HSE - Gone

    Silver 2002 P38 Range Rover HSE - Sequential LPG, BCDC Charger, TPMS, Rear Locker, Wheel Carrier, Bullbar & Spotlights, General Grabber AT2's, Too Much to Mention!

  10. #10
    Join Date
    Feb 2013
    Location
    Gosford, NSW, Australia
    Posts
    2,412
    Well i fitted the Tridon cap and the fuel smell is much worse !

    Maybe I got a faulty one, I'll try swapping it next week

    Steve
    MY96 4.6 HSE P38. Niagara Grey; "The Phoenix"
    MY99 4.6 HSE P38. LPG, Blenheim Sliver; "Voldemort" burnt to a cinder
    MY79 RR Classic, Gone, MY57 Series 1 SWB, Long gone
    P38 write ups and info on my website http://p38.hts.com.au/

Page 1 of 2 12 LastLast

Tags for this Thread

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Search AULRO.com ONLY!
Search All the Web!