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  1. #1
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    Question 850 fuel leak mystery

    After having some work done recently, my 850 T-5R developed a fuel leak. The leak is not severe (no puddles on the drive, MPG more or less the same) but inside the car there is a very strong smell of fuel. This is the case whether the tank is full or nearly empty and anywhere in between. Warm and sunny weather seems to make matters worse. This had never been experienced prior to the work being done. I'm assuming the timing is a coincidence because the work done was unrelated to the fuel system i.e. - in addition to annual service items - throttle housing clean-up, new leads and cap, new air mass sensor, new front oxygen sensor, new thermostat and ECT sensor, new cat back, new K&N air filter and new rear sub-frame bushes.

    The car went back to the same garage that did the initial work and the following was done: fuel tank removed and clips and clamps replaced, fuel hose replaced, fuel pump and sender seals replaced, fuel vacuum hose replaced, canister hose replaced.

    And still the problem pong persists. Quite apart from the smell, I am reluctant to drive the car in case it is unsafe.

    I am aware of a recall for the 850 relating to heat shield attachments but I don't know enough about that to know if it's relevant to my issue, especially with the second round of work done.

    Any obvious causes to investigate? Thanks in advance for any suggestions or pointers.

  2. #2
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    I would contact the garage straight away, they should sort it out.

    But if it was me the first placeI would check, in the absenceof any visible leaks dribbles or damp patches, would be the big plastic nut securing the fuel pump into the tank. They are buggers to get on tight enough without cross threading or nipping the rubber ring/washer out of place. Of course it all seems tight as you re-assemble but can leave a little air gap. not enough for liquid fuel to escape (its at the top anyway) but vapour -yes! and at any stage of teh tank being empty or full. Vapour collects underneath and gets drawn inside especially when the car is moving.

    Anyway thats just based on my experience of replacing fuel pumps, hope it helps.

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    deanrwilkins (Tuesday 14th August 2018)

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    Thanks, Woz. The car is going in to another garage for its MOT next week so I will pass on this suggestion to those techs.

  5. #4
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    woz's Avatar
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    Dean I just re-read your OP more carefully. I thought the fuel pump had been disturbed, but now I realise it was only AFTER the problem arose and throoughly dismatled in an attempt to fix. However, any of the fuel lines could have been disturbed during the initial works underneath the car, and did they replae the fuel filter as part of the service?

    You would imagine any leak was coming out under pressre so would show a damp patch or vapour near where it was coming out.
    Not many low pressure places, the tank, filler neck and connecting rubbers(!!) and fuel return pipe, then the carbon canister which you say has been checked.

    I dont think I have been helpful. Good luck and let us know how it is resolved.
    Cheers
    Woz

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    deanrwilkins (Tuesday 14th August 2018)

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    Woz, thanks for following up.

    To answer your question: no, I don't believe the fuel filter has been changed in the last few months.

    On Friday I picked up the car from the MOT place and there was no smell at all. The techs had taken a look all over the car and could find no sign of a leak. In fact, they were very complimentary about the quality of the work done by the first garage.

    The fuel light came on as soon as I left the garage so I put in around a quarter of a tank; once I got home I parked and left the car in the sunshine for a few hours - lo and behold the strong smell of fuel was back.

    So I think a very low tank means no smell but anything more than enough to keep the fuel light off will still create a smell.

    It's quite a mystery, to me, at least. I cannot think of anything that could've been done during the first lot of work to cause this issue, but it is a nagging coincidence of timing. The first work was: throttle housing clean-up, new leads and cap, new air mass sensor, new front oxygen sensor, new thermostat and ECT sensor, new cat back, new K&N air filter and new rear sub-frame bushes.

  8. #6
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    woz's Avatar
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    I guess the next step is to part fill it with fuel, then take it for the techs to pore over some more...or is it a ll sorted yet?

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    Woz, it gets curiouser and curiouser. The smell has entirely disappeared. Hot weather and cold weather, full tank, empty tank, nearly empty tank. All the variables. I am at a loss to explain it.

    And now the lambda light is back on...

  10. #8
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    Well what a to do!! Perhaps someone spilt some petrol nearby? Lets hope it stays away now.
    Thanks for the update. W


 

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