Petrol cap trap.
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  1. #1
    Moderator Alan S's Avatar
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    Default Petrol cap trap.

    Just posting this as a word of warning to others who may get caught the same way.
    I know absolutely nothing about it nor do I know the guy who posted the emessage but it shows how easily you can get caught out.

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    Hi,
    Thought it was a good idea to buy a locking petrol cap for my XMV6si.
    First off noticed fuel guage needle reading high. Then later car wouldn't start. Removed locking cap put on old cap and it started first time. Didn't quite believe this was happening so tried again somewhile later, and again after a bit car would not start. I noticed that inside the non-locking camp there is a big O ring which is absent in the locking version which incidentally is not a piece of Cit kit. I think it maybe that the non-locking version creates pressure over the fuel by sealing the tank Any ideas

    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

  2. #2
    CitroŽn, what else? smiffy1071's Avatar
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    Default

    I'd say the locking fuel cap was creating a vacuum pressure in the tank, thus causing fuel starvation. does the fuel tank have a breather that might be blocked? Easy way to tell, is when you fill up, does it take for ever for the bubbles to disapear?
    john s
    2005 C5 2.0 VTR Hdi 138, 1986 Kawasaki GPz 750G2

  3. #3
    Moderator Alan S's Avatar
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    I thought of that, but shouldn't there be some kind of tank breathing system apart from a pinhole in the cap?


    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

  4. #4
    CitroŽn, what else? smiffy1071's Avatar
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    Some cars do have a breather and some don't. My AX 11 for example, the breather was a system of pipes that live inside the right rear wheel arch.
    I pulled this out to try to un-block it, because it took ages to fill the tank.
    I renewed every pipe there, but it still was unsatisfactory. I got rid of the car in the end! john s
    2005 C5 2.0 VTR Hdi 138, 1986 Kawasaki GPz 750G2

  5. #5
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    Reasonably current cars don't have a breather to the atmosphere for emissions purposes - they aren't allowed to vent hydrocarbons. Even the UK versions without cats would still have evaporative emissions controls AFAIK.

    I've read that they often build up a slight pressure in the tank while running. I guess in this case it was possibly designed into the system to use this slight pressure for proper fuel delivery - the locking cap not having an o-ring preventing this and causing starvation?

    Stuey
    Last edited by Stuey; 2nd October 2005 at 07:54 PM.


    2003 PEUGEOT 206 GTi

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