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Thread: Ignition problems - no spark :(

  1. #1

    Ignition problems - no spark :(

    Hi all,

    Just having some issues with the ignition at the moment..no spark!

    This is what I am running:

    2ltr Pinto
    Bosch SU12 with internal resistor
    Crane Cams/Fireball XR700 Ignition Module
    Bosch distributor with hall effect trigger (no points)

    These are the tests I've done so far:

    1. Check spark plugs - they were clean and gaps were good.
    2. Check timing - have lined everything at TDC and rotor at dizzy is in correct position
    3. Check spark from coil - no spark from lead when close to ground or with bulb test
    4. Check resistance of coil - 3 ohms for primary and 10k ohms for secondary which is good
    5. Check voltage from ignition module - 12v coming from ignition module when ignition is switched on
    6. Check voltage across coil terminals (primary) when cranking - mulimeter registered 9v when cranking which means voltage is switching between 12v and 6v which is good.

    Everything *SEEMS* to be ok.... any thoughts from people more electrically talented than me??

    Cheers, Tom

  2. #2
    Sounds like the electronic ign ( trigger ) is at fault not allowing the field to collapse in the coil. I would install points, for the moment, to see if there is a spark from the HT coil.

  3. #3
    Thanks for the reply peteleo. I might see if I can get my hands on some points tomorrow.

    Just for my own knowledge - if the voltage is alternating between 12 volts and 6 volts at the coil terminals while cranking, does that mean the field is collapsing?

    Cheers, Tom

  4. #4
    There should be 12v at the primary with ign on. When you start the car there will be a 1-2 voltage drop across the primary due to a load from the starter and additional load if a ballast resistor is in line with the primary. So a minimum of 9v should be sufficient to operate a coil. As the coil builds up a field min. of 8K volts a triggering system ie. points or electronic will collapse the field at the secondary causing a high voltage spark ( HT side ) at the center of the coil. If you have a pulsating 12v - 6v at the primary is usually caused by a capacitive discharge unit or electronic ign triggering system fault. Pete

  5. #5
    Pete you were spot on! I was wrong about the distributor though... when I looked at it properly I realized it wasn't hall-effect but an optical trigger set up. I put a test light from the negative terminal and to ground and the was no on-off flicker when I cranked, just dimmed slightly. Which pointed it back to the ignition coil which wasn't collapsing the field, eve though it was registering the signal.
    Replaced it - started straight away.
    Thanks for the info once again Pete

  6. #6
    Tom,

    Glad to hear it worked out. I've had these type of problems with early pertronix units were the triggerring magnets were coming loose from the holder rings. Later pertronix sealed the magnets in the ring. Another failure of the unit was due to too low resistance on the primary side of the coil.

    Regards,

    Peter

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