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Thread: No spark after 12 volt conversion

  1. #1
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    No spark after 12 volt conversion

    Hi guys I'm back on my 53 Willys truck project.
    Got the motor back together and have fuel but no spark. I converted to a pertronix but can't figure out why I'm not getting any spark.

    With the key on I have 12 volts on the postive side of the coil, but when I start to crank I only see 9-8 volts on the same terminal.

    Ideas are welcome....help please
    Last edited by Btroy; 10-12-2018 at 02:45 PM.

  2. #2
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    Quote Originally Posted by Btroy View Post
    Hi guys I'm back on my 53 Willys truck project.
    Got the motor back together and have fuel but no spark. I converted to a pertronix but can't figure out why I'm not getting any spark.

    New flame-thrower coil added as well.

    With the key on I have 12 volts on the postive side of the coil, but when I start to crank I only see 9 volts on the same terminal.

    Ideas are welcome....help please
    Cap was removed and rotor is turning CCW as expected.

    Also measured voltage on negitive side of coil while cranking and it is thwe same as the postive side 9-8 volts.
    Last edited by Btroy; 10-12-2018 at 02:54 PM.

  3. #3
    Super Moderator LarrBeard's Avatar
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    Coil voltage

    Quote Originally Posted by Btroy View Post
    Cap was removed and rotor is turning CCW as expected.

    Also measured voltage on negitive side of coil while cranking and it is thwe same as the postive side 9-8 volts.
    The negative side should be at ground potential with the points closed. Is that voltage wiggling as you crank?

  4. #4
    Super Moderator LarrBeard's Avatar
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    No Spark

    Quote Originally Posted by Btroy View Post
    Cap was removed and rotor is turning CCW as expected.

    Also measured voltage on negitive side of coil while cranking and it is thwe same as the postive side 9-8 volts.
    What system have you installed? It appears that most of these systems use Hall effect magnetic sensors to replace conventional points, but the circuitry still makes and breaks the coil primary circuit. Check the spacing of the magnet from the sensor coil.

    Do you get a spark with a clip lead from battery to the + terminal of the coil (just ground the - terminal) but be careful, 30 kV will knock you on your fanny.

    If you are using a digital voltmeter to read the negative side of the coil, the meter may not respond quickly enough for you to see the make/break action. See if you can find an old analog meter.

    It's hard to do electrical troubleshooting via email, but we'll poke at it.

  5. #5
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    I went ahead and bought a new electronic distributor from our host. I am still not getting any spark.
    I have a flame thrower coil. The instructions say it has to be an internal resistor type or I will need a resistor.

    To answer the question. No I do not get any spark when going from the battery + to the coil.

    Truck was converted to 12v with a new wiring harness as well.
    Last edited by Btroy; 10-19-2018 at 12:13 PM.

  6. #6
    Super Moderator LarrBeard's Avatar
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    Quote Originally Posted by Btroy View Post
    No I do not get any spark when going from the battery + to the coil.
    Let’s try to take just one step at a time.

    If you have a multimeter, check the coil for an open winding. Measure from the + post to the - post on the coil. That is the Primary winding of the coil, the winding that gets a pulse of current from the distributor if everything goes well. The Primary should measure a fairly low resistance, I think I saw some Flamethrower resistances about 3 or 4 ohms.

    The Secondary will measure a lot more resistance – I would guess maybe even 6 or 8 thousand ohms. Measure that from the center contact of the tower to the – post of the coil. This verifies that we have a good coil. (As a check, an old 6-volt Delco-Remy coil measures 1.5 ohms primary, 8,800 ohms secondary)

    Here is a YouTube video showing just how to do this:

    https://www.youtube.com/watch?v=dtMnD8YJo2Y

    (and he's right - he should get clip leads)

    Now, let’s try to get a spark out of the coil. Take a look at the sketch at the bottom of the note here.

    Make sure that the negative (-) side of the coil, the negative terminal of the battery and the engine block and frame are all tied together electrically. For this test, I would suggest some good jumper wires or clip leads. Don’t trust the case of the coil to give you a ground. Paint is an insulator. Don’t worry about resistor or no resistor just yet – we’re just trying to get a lightning bolt out of the tower of the coil.

    It would help to have a helper, this is really a four hand task.

    Hold the high voltage (HV) lead from the tower on the coil close to the engine block - about a 1/16 or 1/10-inch. Have your helper tap the clip lead to the + terminal of the coil and remove it. As the helper taps, you should be getting a spark from the HV lead to the block or frame. TAP-ZAP; TAP-ZAP.

    If we get a spark now, we have verified that the coil is good.

    Let us know what you find and we will go to the next step from there.
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    Last edited by LarrBeard; 10-19-2018 at 02:53 PM.

  7. #7
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    Ok looks like the new coil is bad, as from + to - it measures 03.4. From center to - my meter does not move.

    I will get another coil.

    Thanks for your assistance. Will reply once I get another coil.

  8. #8
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    Ok new coil and I get spark with it as in drawing.
    But when I connect up the wires
    It cranks but no fire from the coil tower now?

  9. #9
    Super Moderator LarrBeard's Avatar
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    OK - some progress.

    Just so I can get a good idea of just where we are, what is the Pertronix part number for your ignition module?

  10. #10
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    That has changed, I went ahead and bought a distributor from our host with the electronics
    In it.

    It appears I maybe burning up
    The coils. Now when I test the secondary
    It is showing 9.9 on one and 10.6 on another coil I tried.I have yet another older coil that is showing 8.6 on the secondary side.
    All 3 coils still produce spark at the secondary side
    Last edited by Btroy; 10-25-2018 at 05:12 PM.

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