Drop in spark

Discussion in 'Electrical' started by el.mariachi, Jan 21, 2011.

  1. el.mariachi

    el.mariachi New Member

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    Hi There,

    Ive got a 1990 heritage softail 1340, I recently had a full strip down and rebuild of the engine seals & frame powder coated.
    I got her home and cranked her up and she ran awesome.

    A week later I pulled her out of my room started her up & got her to running temp shut her down then 10 mins later went to start her up & no go I dropped the plugs & found that when I pressed starter button spark dropped off to nothing?
    When I released the starter button spark slowly returned to full spark.

    Any Ideas?

    Please Im deserate for a ride.

    Cheers El
     
  2. Hoople

    Hoople Account Removed

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    How did you determine the spark was stronger when you did not have your finger on the start button? Did you bypass it somehow in order to get the engine to crank. Are you working with a 1990 shop manual?

    I have a 1991 Softail manual and can help but I don't know how close the schematics are to the 1990.
    On your ignition coil do you have two white wires going to 1 stud and 1 pink wire going to another stud.

    Before swapping any parts, the very 1st thing you need to do is determine if a voltage drop exists at the ignition coil. Take a quality VOM and place it across the battery posts. Crank the engine (without starting) and record the voltage. The move the meter to the coil and measure the voltage at the White wire stud on the coil and Frame ground. Record the voltage while cranking (not starting).

    Those two voltages should be pretty close to one another (within .5 volts would be nice). If they are not, that is your problem. Based on what you said, I would expect those voltages not to be close.

    Having 2 meters hooked up at the same time is ideal and makes it easy to make an accurate comparison.
     
  3. el.mariachi

    el.mariachi New Member

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    I was working on her at night & had the plugs out sitting on the heads with the leads hooked up to see if i had any spark to start with and as i mentioned above thats what i observed when releasing the starter button.

    Iv got the pink wire going to the top post with a white wire on the bottom post.
    Theres also a blue wire on the top post with another white wire on the bottom post both of which come from a black module type box by the battery.

    And no i dont have a manual! I should get one!

    Thanks Hoople I'l give that a crack & let ya know what hapens
     
  4. JBC2565

    JBC2565 Junior Member

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    Definately get the manual.
     
  5. Hoople

    Hoople Account Removed

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    HD must have made a few changes in 1991 because the manual I have shows 2 white wires as being source voltage and on your bike they both go to ignition module. My print also does not show a blue wire.

    Readings those voltages from my earlier post may be a waste of time because the white wires in my manual are different than what you actually have. I thought maybe the 1991 manual would work but it looks like you really need to get a schematic of your exact bike.
     
  6. el.mariachi

    el.mariachi New Member

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    Thanks Hoople I'l try it anyway
     
  7. maine-e-axe

    maine-e-axe Junior Member

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    Do you have good "grounds" with the new powder coat job
     
  8. Jack Klarich

    Jack Klarich Expert Member

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    First thing I would check, then check for arcing and cracks in the coil, probe the wires coming out of the nose cone for power with a test light with the ignition on follow it to the coil