Crank Position Sensor Wires Question | FerrariChat
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Crank Position Sensor Wires Question

Discussion in '308/328' started by Big Daddy, Dec 18, 2013.

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  1. Big Daddy

    Big Daddy Karting

    Jan 3, 2009
    212
    Albuquerque, NM, USA
    Full Name:
    RJ
    #1 Big Daddy, Dec 18, 2013
    I tracked down an ignition miss to the wires that connect to one of the crank position sensors. I had to strip off the black outer insulation, and I found that one wire was fully insulated, while the other wire was insulated only on the ends. The part of that wire under the outer cover was bare. The fully insulated wire had developed a crack in the insulation, and since the other wire was bare the signal was jumping between them.

    I want to replace the wires going to all three crank position sensors and replace the connectors with weather proof connectors to avoid any problems in the future. I am planning to use TPFE multi stranded copper wires with WeatherPack connectors.

    My question is this: Is there a reason why they used the one insulated wire and the one uninsulated wire? I am thinking that maybe the uninsulated wire is supposed to act as a shield for the other wire.

    Would it work just as well if I used two insulated wires? If so should I use a twisted pair of wires, or use some kind of foil shielded wires? Or should I use a two conductor cable?

    Also, does anyone know what guage wire I should use? Thanks.
     
  2. andyww

    andyww F1 Rookie

    Feb 7, 2011
    2,775
    London
    #2 andyww, Dec 18, 2013
    The wires are screened, with an outer braid which is grounded and an inner conductor.
    The voltage output from the sensors is low so the screening adds to interference suppression.
    I am not sure how easy it would be to just replace the wires as its a molded assembly at both the sensor and the connector end. Its probably best to replace the entire thing, they are not that expensive.
     
  3. jon s

    jon s Formula Junior

    Mar 9, 2005
    509
    pocasset ma
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    jon shoukimas MD
    #3 jon s, Dec 18, 2013
    or you can make up new leads with fine, one stranded, shielded cable and use the shield as the other lead (ground). should work fine. jon s p.s. i love liquid vinyl for shrink wrapping these assemblies. the pvc insulation on a lot of the engine compartment wiring on my 18 year old bmw has started to crack and fall apart and the stuff has saved a lot of rewiring time. it's waterproof and easy and has reasonable mechanical strength. good luck.
     
  4. Big Daddy

    Big Daddy Karting

    Jan 3, 2009
    212
    Albuquerque, NM, USA
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    RJ
    #4 Big Daddy, Dec 19, 2013
    AndyWW: Do you know of a source for the wires? Thanks.
     
  5. Crowndog

    Crowndog F1 Veteran

    Jul 16, 2011
    7,042
    Fairfield,Pa
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    Robert
    #5 Crowndog, Dec 19, 2013
    I believe any stray energy getting to that Center conductor could be taken as a signal hence the braided shield. It would be wise to just replace the sensor/wire as a whole. They are available from superperformance but I do understand a sleight modification to the mounting plate is in order but easy to effect.


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  6. Crowndog

    Crowndog F1 Veteran

    Jul 16, 2011
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    Robert
    #6 Crowndog, Dec 19, 2013
    I happen to have two used OEM sensors left over from my project. Wires still soft.


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  7. Big Daddy

    Big Daddy Karting

    Jan 3, 2009
    212
    Albuquerque, NM, USA
    Full Name:
    RJ
    #7 Big Daddy, Dec 19, 2013
    Crowndog: I was actually talking about the wires that the sensor connects to. As far as I can tell the sesors and the wire attached to them are okay. They all connect to wires coming from an eight wire connector that plugs into the inner fender. It is the wires from that connector that then plug into the sensor that are going bad because the insulation is cracking.
     
  8. Crowndog

    Crowndog F1 Veteran

    Jul 16, 2011
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    Fairfield,Pa
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    Robert
    #8 Crowndog, Dec 19, 2013
    Could you provide a picture of the wires as I am sure that suppliers such as Mouser or Allied will have cable that can be substituted.


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  9. alhbln

    alhbln Formula 3
    Consultant Owner

    Mar 4, 2008
    1,749
    Berlin, Germany
    Full Name:
    Adrian
    #9 alhbln, Dec 20, 2013
    This type of shield wire is called coaxial cable. You can still use Weatherpack, Deutsch or Econoseal connectors at the end, but AMP/Tyco connectors will be more period correct (but are not sealed against dirt/humidity).
    The shielding via the grounded wire helps suppressing interferences on the VR sensor signal, a straight or twisted pair wire will not have enough shielding to avoid interferences. If you can't find a matching coaxial cable type at your electronics supplier, have a look at heavy duty microphone coaxial cable from your local music store.
     

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