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Hot Rods 302 weak spark

Discussion in 'The Hokey Ass Message Board' started by babblewon, Feb 13, 2017.

  1. babblewon
    Joined: Aug 19, 2007
    Posts: 202

    babblewon
    Member
    from cali

    ok so I posted about the ignition wiring a couple weeks back and thought I had it figured out. I wired it all up and have weak spark when I pull the plug and put it to ground when cranking. (Motor won't start, no coughing or anything, got fuel)
    It's a late 80's fuel injection mustang 302 converted to carb.
    I used:
    1985 mustang distributor (steel gear)
    Standard gm round style coil
    1985 replacement ignition module box
    I attached a quick drawing of how it's wired. What is wrong? Do I need a different coil? Did I wire it wrong? I've been all over the mustang forums and seen several different duraspark wiring diagrams. I also tried a different coil with the same results. The only part not new is the plug wires, but they looked ok.
    I attached the duraspark diagram I went off too.
     

    Attached Files:

  2. onetrickpony
    Joined: Sep 21, 2010
    Posts: 859

    onetrickpony
    Member
    from Texas

    You may have wrong value resistor or a coil with an internal resistor. Byp*** the resistor and see what happens.
     
  3. babblewon
    Joined: Aug 19, 2007
    Posts: 202

    babblewon
    Member
    from cali

    Byp***ed the resistor and got some good spark. Thanks! Now on to the carb issue haha
     
  4. hotroddon
    Joined: Sep 22, 2007
    Posts: 28,240

    hotroddon
    Member

    If that is the 1985 CA Duraspark II module, it likes a really low resistance coil - around .3 to .6Ω and a ballast resistor of around 1.2Ω (stock in the Mustang was a resistor wire)
     
  5. babblewon
    Joined: Aug 19, 2007
    Posts: 202

    babblewon
    Member
    from cali

    Ya it's the stock duraspark box. I'll get the wire style resistor and stock replacement coil
     
  6. You don't need to run the resistance wire if you use a coil with roughly the same overall resistance; 1.5 to 1.8 primary ohms will do it.
     
  7. babblewon
    Joined: Aug 19, 2007
    Posts: 202

    babblewon
    Member
    from cali

    My coil is at 1.3
     
  8. You can probably get away with that, even though it's a bit low. But I'd keep a spare Duraspark box handy....
     
  9. sunbeam
    Joined: Oct 22, 2010
    Posts: 6,393

    sunbeam
    Member

    Measure the voltage on the pos. side of the coil cranking it should be no lower than 8.5 - 9 volts
     
  10. DraVen_West
    Joined: Jan 19, 2017
    Posts: 3

    DraVen_West

    This is how i have my wired[​IMG]
     

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