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308QV Ignition/Plug Wire Testing?

Discussion in 'Technical Q&A' started by PhilB, Sep 13, 2009.

  1. PhilB

    PhilB Formula 3
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    Feb 17, 2004
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    What's the consensus on how to test the wires for a QV during the major, and what the Ohm reading should be?

    I've searched/read every thread on here. There is no consistency on this question. Some threads say Ohms should read zero, others say 300.

    I'm getting inconsistent readings and am not sure what, if anything, is wrong. I'm in the midst of the service I have the front (nearest the cabin firewall) distributor cap and wires off. Car was running fine before I started the service. All components are original to the car. Car is an '84 US spec, with black extenders.

    My meter is set to the x10k scale. I'm checking every component on the car, separately (plugs are disconnected form the extenders, extenders are disconnected from the wires, etc.).

    Readings on the wires are not consistent:

    - All 4 extenders are reading identical: 5
    - *All 4 plugs are reading identical as well: 5
    - Coil wire: 80
    - Cylinder 1 wire: 5
    - Cylinder 2 wire: 0
    - Cylinder 3 wire: 0
    - Cylinder 4 wire: 0

    *(Even though new plugs are getting installed, I figured I'd check them anyway more so to see if something was wrong with my meter.)

    I figured it was unlikely for three wires to fail - especially after the car was working fine when I shut it and started the service. Then I thought maybe I had a bad end on wires 2, 3 and 4. So I (randomly) took the #3 wire, removed it from the cap, thoroughly inspected the spark plug end which looked fine. I have one meter probe connected to the spark plug extender clip on the wire. I then pressed the Ohm meter probe to the distributor end of the wire. Still 0. Then I inserted the meter probe into the pin hole (made by the distributor connection) on the wire, still 0. So then I cut a 1/4" of wire off at the cap end to get a clean cut. Measured again, still 0.

    Ok. So I could buy new wires, but before I do that I'd still like to understand these readings. If the #1 wire wasn't reading 5 (same exact as extenders and plugs), I'd think I had one bad wire, the #1 wire. It's also odd that the coil wire is reading 80. The wires are all identical (I removed the silicone sleeves to check), so I presume they should all be reading 80, 5 or 0.

    Any thoughts. Anyone else in the midst of their service that checked their wires?

    Phil
     
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  3. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
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    No I didn't get zero ohms for my plug wires. I got approx. 350 ohms per foot. I can get you my exact readings if you need them.
     
  4. PhilB

    PhilB Formula 3
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    Interesting. The #1 wire - the shortest - is reading 5, so clearly #2-4 - which are longer - should not be zero.

    Phil
     
  5. Brian Harper

    Brian Harper F1 Rookie
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    I don't get it. Why did you put zero if you didn't get zero as a reading?
     
  6. miketuason

    miketuason F1 World Champ
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    Feb 24, 2006
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    Phil, you mentioned that you have the black extenders,
    I thought QV suppose to comes with red extenders, at least
    my QV does and it runs fine.
     
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  8. CliffBeer

    CliffBeer Formula 3

    Apr 3, 2005
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    Another check for your wires/extenders: start the car in the garage (with the garage door open) at night with no lights on - if there's sparks then you know you've got some wires/extenders to replace.

    You'd be surprised how many sparks you'll see on a 308/328 ignition system that has some wear/miles on it!
     
  9. PhilB

    PhilB Formula 3
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    #7 PhilB, Sep 14, 2009
    Last edited: Sep 14, 2009
    The extenders have been black since I owned the car - quite a number of years.

    I thought the black ones were fitted to US Spec QVs and have some additional resistance or RFI suppression over the red ones. I thought that the red ones were fitted to Euro Spec QVs and have no resistance. And lastly, I thought the was another type of black extender, but slightly shorter than the one fitted to the US Spec QV, which was fitted to all 308s (all markets) prior to 1982. I do recall reading that each of these three extenders have different lengths as well.

    Assuming the extender for a US Spec QV is part #115647, it looks like one parts supplier agrees that the QV extenders should be black:

    http://www.ricambiamerica.com/product_info.php?products_id=193274

    And one thinks they should be red:

    http://www.italiancarparts.com/ignitionwires/ignitionwires.html

    Doesn't it figure, as with everything on these cars...? ;-)

    Again, car was running great and given all my extenders are reading the same Ohms, I presume the extenders are fine. I'm just trying to understand the readings on the wires.

    Phil
     
  10. davehelms

    davehelms F1 Rookie

    Jan 3, 2004
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    Phil,

    Do you mean that the meter showed no movement or reading...ie, open circuit or a full scale reading of zero resistance?

    It is common for us to find 3 or 4 wires out of the 10 to be open...ie, conductor wire broken. It is one of the down falls of the Cavis wire being loose wound on the fiberglass core, quite fragile.
     
  11. PhilB

    PhilB Formula 3
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    Dave - exactly, needle (on the Ohm meter) didn't move on wires 2, 3 and 4 when tested (open circuit).

    Again, car was running fine before I started the service.

    And I'm using my best "white glove/virgin deflowering/handle with care" light touch that I can, so I doubt the wires were damaged when I removed them from the plug extenders (not the first time I did this either, been changing plugs 1x year for 10 or so years now).

    Phil
     
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  13. davehelms

    davehelms F1 Rookie

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    #10 davehelms, Sep 15, 2009
    Last edited: Sep 15, 2009
    OK, that makes more sense, zero resistance is a pretty good solid core wire...open is no conductivity. You 'thought' it ran well...you will feel and hear the difference. Its one of the problems of this business, many think everything is perfect until they feel 'perfect'.

    There are a number of wire choices these days...you need a new set. I happen to fancy our 7mm Taylor Spiral core we made, others like the Magnecore, some like Accel
     
  14. boatr2001

    boatr2001 Karting

    Oct 3, 2006
    88
    Rockford,IL
    I'm currently struggling to understand do I need resistance or non-res extenders. I've read about every thread and find myself more and more confused. Manufactured 83, Euro 308QV, 803A digiplex, NGK BP7ES plugs. I'm replacing the wire set thru Kingsborne and need to replace extenders as well. I've found a mix of both extenders on the car now. Resistive or non-resistive, that is the question ;) Thanks!
     

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