A friend of ours has a 2005 Ford Mondeo 2.0 TDCI which is a common rail turbo diesel.

Today, lots of white smoke came from under the bonnet (hood) which appeared to be coming from the fuel filter. The body of the fuel filter was very hot. She has parked the car and is not using it fearing (quite rightly) the risk of an engine fire.

I'll be taking a look at it tonight but can't think of any reason that a fuel filter would become so hot and emit smoke. Has anyone come across a similar scenario or have any suggestions of what I ought to check? My first thoughts are the condition and security of the fuel pipes but any other suggestions would be greatly appreciated.

  • 1
    Are there are large cables in that area? But could the fumes be coming from below the filter - one of the leak off return pipes may have split and is dropping fuel onto the exhaust?
    – Solar Mike
    Commented Oct 1, 2018 at 15:10
  • A cracked exhaust manifold or exhaust pipe?
    – GdD
    Commented Oct 1, 2018 at 16:32
  • 1
    I'm wondering if there is an injector stuck open, which is forcing compressed air/fuel back into the injection system? It seems possible if the fuel filter was getting charged with hot air/fuel from the combustion chamber, it might do exactly this ... just spitballing, though, because I don't even know if this is possible. Commented Oct 1, 2018 at 17:20
  • What is the fuel pressure in the common rail feeding the injectors?
    – Solar Mike
    Commented Oct 1, 2018 at 21:39
  • @Pᴀᴜʟsᴛᴇʀ2: seems unlikely. The pressure in such common rail systems is quite high, up to 29,000 PSI. It is used to inject fuel during the compression cycle directly into the cylinder.
    – Daniel
    Commented Oct 2, 2018 at 13:59

1 Answer 1


Well I’ve been out and investigated tonight. It transpires that the fuel filter sits in a metal bracket which it bolted to the strut mount. This bracket had worked lose and dropped down. Immediately underneath it sits the alternator and this bracket shorted out the wiring on the back of the alternator.

I’ve reattached the bracket to the strut top but sadly the wiring on the back of the alternator seems to be fried as the car runs and drives but the battery light stays on.

Thanks to all for your input.

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