X250 engine earth strap and failed hot start.

Discussion in 'Tech/Mech General' started by Techno, Nov 19, 2014.

  1. Techno

    Techno Funster Life Member

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    I've found several threads across the web detailing the same symptom of failure to re start a hot engine.
    Normal starting from cold is fine but after a journey the first attempt at restart often fails.
    The popular answer is to replace the engine earth strap.
    [​IMG]
    This picture borrowed from O&AL
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    I've not had chance to prove it yet but I did 10 consecutive cold starts and all fired as fast as you can say 1 2 3 with no hesitation. I've replaced with a shag of 70mm welding cable.
     
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  2. Techno

    Techno Funster Life Member

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    Some may ask why would being hot change things?
    I believe it is to do with increased cylinder pressure and thus higher cranking load.
     
  3. TheBig1

    TheBig1 Funster Life Member

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    as you know, but others may not, the easy, belt and braces way to check if its the earth strap is to connect a good jump lead from the battery negative to the engine block. if the problem goes away with the jump lead connected, then its fair to assume the earth strap has rotted. a pretty common fault on many different vehicles, not just Fiat ducatos
     
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  4. jonandshell

    jonandshell Funster

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    It could be another reason Andy.

    The resistance in the earth strap could cause all sorts of problems with the analogue inputs to the ECU and this could screw things up.
     
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  5. Ed Excel

    Ed Excel Funster

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    Set your Multimeter to the lowest resistance setting and start the engine. Touch a probe on the negative battery pole and the other to a bolt on the chassis. You should get at least 0.3 Ohms. If the readout stays at zero, the earth cable or chassis bolt is either loose or corroded. Do similar between an engine bolt and a chassis bolt. If the instrument doesn't register you've a problem with the engine strap.
     
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  6. Techno

    Techno Funster Life Member

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    My earth strap doesn't look rotted but it doesn't look especially healthy. Why use bare copper at all?
     
  7. vin0114

    vin0114 Funster

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    Thanks Ed, very good tip.
     
  8. Ed Excel

    Ed Excel Funster

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    It's not a great environment they're in and PVC's only happy up to 70C. I imagine these straps can get hotter than that.
     
  9. Techno

    Techno Funster Life Member

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    Would this not be the same engine hot or cold? remember it is ONLY a hot engine fault.
     
  10. Ed Excel

    Ed Excel Funster

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    If you're starting off with a high resistance connection then any temperature rise will exacerbate the problem.
     
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  11. pappajohn

    pappajohn Funster Life Member

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    Easiest way to test a copper earth wire is to grasp it firmly then pull and push as hard as possible.
    i've seen a few which looked good but soon broke when sujected to the above.

    If it doesnt break its good.

    Doesnt mean the connection between cable and battery/engine/body is good though.
     
  12. Techno

    Techno Funster Life Member

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    I have good connection now John so we'll see next time I restart it hot (y)
     
  13. Techno

    Techno Funster Life Member

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    I've had many a car over 16 yrs old (one over 20) and never had an earth strap problem. The reason I started this topic is because it seems to be particularily common to X250's
     
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  14. Ed Excel

    Ed Excel Funster

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    Did your cars have an engine compartment floor pan? Has the x2/50? My car has. It gets mentioned in every MOT as an excuse for not checking anything behind it.
     
  15. Techno

    Techno Funster Life Member

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    no and yes
     
  16. Badknee

    Badknee Funster

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    I've been driving for about six months now and I've never had a problem ;) :LOL:
     
  17. jonandshell

    jonandshell Funster

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    The strap could warm up with the continuous load of charging your battery bank. It provides the negative for your alternator remember!

    Don't get these problems with Transits........:reel::BigGrin:
     
  18. Techno

    Techno Funster Life Member

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    Exactly
     
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  19. Techno

    Techno Funster Life Member

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    Perhaps more interestingly.
    As I said the commonly reported fault is a failure to restart when hot BUT that is only on the first attempt, they start on the second go.
     
  20. Ed Excel

    Ed Excel Funster

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    That's Fiat design for you. Looks good!!
     
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