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Ignition lead question

Discussion in 'T3 & T4 Tech Help Clinic' started by Dapom, Jan 10, 2016.

  1. Dapom

    Dapom Well-Known Member

    Messages:
    805
    Location:
    Brisbane
    Hey all :)
    So in my so far never ending quest for the answer to my current problem with my bus (see 'starts,idles,won't drive') I have tested resistance of my ht leads to plugs and king lead from coil to cap.
    All leads to plugs read 1020 ohms.
    King lead (coil to cap) reads 0. This indicates open circuit right? So is this correct or should resistance read the same as a lead to the plugs?
    Thanks in advance for any info :)
     
  2. cbus

    cbus Well-Known Member

    Messages:
    13,570
    Location:
    sunshine coast
    Open circuit means the circuit is cut. ie not a circuit= no flow
    assume you are testing original type wire core leads?
    the multimeter will read 1 until you have a circuit.
    series of 0.00 will indicate you have circuit with zero resistance.
    Obviously you need a 'circuit' [for test] and seeking to test continuity in the lead.
    that will apply to te coil lead if its in good nick.
    sounds like you are testing the plug leads thru the spark plug caps/connectors?
    they have inbuilt resistance as standard. 1k ohm, sounds right .

    the other test is at night time with engine running , check for stray spark trails along the leads . A lot or actual parks jumping [usualy audible] means the insulation is compromised and lead needs replacing

    test for circuit between alternate cap contact points and centre 'electrode'. there shouldnt be a circuit. if there is then replace cap
     
    Last edited: Jan 10, 2016
  3. Dapom

    Dapom Well-Known Member

    Messages:
    805
    Location:
    Brisbane
    Hey cbus :) yes they're original type leads not silicone or such like.
    Yes I tested leads end to end. Ie including spark plug connector hence the resistance.
    I suppose my question was whether the king lead should also have resistance.
    Thought it shouldn't have but was looking for confirmation :) thankyou :)
    Just tested cap and no circuits :)
     
  4. syncro

    syncro Well-Known Member

    Messages:
    10,371
    Location:
    Southern Highlands
    No it should be 0.

    The resistance is in the spark plug connectors.

    For the coil lead the resistance is in the rotor.
     
  5. Dapom

    Dapom Well-Known Member

    Messages:
    805
    Location:
    Brisbane
    Great thanks guys :)
     

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