If I were to connect an ignition coil directly to a battery

Discussion in 'The Garage' started by indr, Sep 27, 2012.

  1. indr

    indr .

    Joined:
    Feb 22, 2010
    Oddometer:
    501
    Location:
    .
    ...
    #1
  2. CycleDoc59

    CycleDoc59 Wrench Rider

    Joined:
    May 24, 2006
    Oddometer:
    984
    Location:
    East Virginia
    Each time you break the connection to the battery, the plug will fire.

    I sometimes bench-test coils by connecting the coil to a battery and sparkplug.
    Or better, to a spark-tester with a much wider gap of 10mm or more.
    #2
  3. Turkeycreek

    Turkeycreek Gringo Viejo

    Joined:
    Oct 26, 2010
    Oddometer:
    1,338
    Location:
    BanĂ¡michi, Sonora, Mexico
    This is a good way to install a flame thrower. Just need a source of gas or propane, a metal tube and you are in business
    #3
  4. CycleDoc59

    CycleDoc59 Wrench Rider

    Joined:
    May 24, 2006
    Oddometer:
    984
    Location:
    East Virginia
    Cars would sometimes get a spark plug installed in the side of the tail pipe, downstream
    of a propane bottle connection. Don't tailgate.
    #4
  5. ragtoplvr

    ragtoplvr Long timer

    Joined:
    Oct 18, 2007
    Oddometer:
    6,880
    Location:
    central USA
    For the flame thrower they used a model T coil that had points that vibrated all the time to drive the flame thrower plug.

    Or you could use a normal 12 V relay with 2 sets of contacts, one set wired as a buzzer, the other drives the coil.
    If you used it a lot, it would not last long but for a novelty it is perfect When gas was 20 cents a gallon this was fun.

    Rod
    #5
  6. Storm Shadow

    Storm Shadow Thread Ninja

    Joined:
    Jan 9, 2011
    Oddometer:
    1,499
    Location:
    Arashikage Clan
    a proper flame thrower, is run by gasoline, or petrol, force fed by compressed air into the petrol tank, to push it out. pump and ignition were two separate buttons too, so u could spray petrol 100 meters away, yes they do travel a bloody long way, not like movies, to run into a bunker, and then ignight it.

    ive often thought about a efi fuel pump 12v battery, to make something, quight illegal...
    #6
  7. Two Speed

    Two Speed Adventurer

    Joined:
    Dec 12, 2010
    Oddometer:
    74
    Location:
    a handbasket
    Since you don't mention if you want to make things go boom as above, or jury rig an existing ignition system, if you hook it up and leave it powered,
    1. The engine won't turn off when you turn the key off.
    2. You'll burn the coil up if its "on" and not running.
    3. Drain your battery if the engine isn't running.
    #7
  8. Benesesso

    Benesesso Long timer

    Joined:
    Jul 29, 2008
    Oddometer:
    9,898
    Location:
    West of Phoenix, Arizona
    One more little goodie. 6V car coils are meant to run at ~6.7 volts. 12V car coils are built to run at ~9-10 volts continuously. They'll take 12-13 volts intermittently.
    #8
  9. FixerDave

    FixerDave KLR650 - XR200R

    Joined:
    Jul 13, 2006
    Oddometer:
    414
    Location:
    Victoria, BC, Canada
    Off topic, but my understanding is that flame throwers are actually legal (used in agriculture or something or other). As a topic, it comes up in the anti/pro-gun rants. Sure, why ban X when flame-throwers are legal?

    On topic again... a coil is just a transformer. They only work when the input is changing. 12v, just connected - not changing, will just heat the coil up, nothing at the output at all. You need to make and break the input to get spark on the output.

    David...
    #9
  10. Storm Shadow

    Storm Shadow Thread Ninja

    Joined:
    Jan 9, 2011
    Oddometer:
    1,499
    Location:
    Arashikage Clan
    ah different countries
    #10
  11. Wasser

    Wasser Spilt my beer

    Joined:
    Oct 31, 2009
    Oddometer:
    5,256
    Location:
    Colorado
    That's why every owner of an old Chrysler product always carried a spare ballast resistor in the glove box or, a jumper wire to get to the parts store. :D
    #11
  12. Benesesso

    Benesesso Long timer

    Joined:
    Jul 29, 2008
    Oddometer:
    9,898
    Location:
    West of Phoenix, Arizona
    +1. I was wondering how long it would take before someone jumped in on this. Let's wait and see if anyone can explain why they did it that way. :1drink
    #12
  13. Beezer

    Beezer Long timer

    Joined:
    Oct 26, 2004
    Oddometer:
    6,060
    Location:
    Anchorage, formerly Spenard (hub of the universe)
    when the starter engages, the battery voltage drops, so the coil is designed to run on the lower voltage (about 10V) to produce a hot spark. once the engine starts and the system resumes normal voltage, current to the coil is reduced by the ballast resistor. in start mode the coil is wired to the main buss through the key switch. in normal run mode the key switch puts the resistor is in series with the coil so the voltage will be reduced to the coil only
    #13
  14. Benesesso

    Benesesso Long timer

    Joined:
    Jul 29, 2008
    Oddometer:
    9,898
    Location:
    West of Phoenix, Arizona
    Nailed it. :clap
    #14
  15. MotorradMike

    MotorradMike MIL-TFD-41

    Joined:
    Aug 17, 2008
    Oddometer:
    1,026
    Location:
    Mallorytown Ontario
    So why are 6V coils meant to run at 6.7V?
    #15
  16. muddywater

    muddywater Been here awhile

    Joined:
    Oct 1, 2007
    Oddometer:
    688
    Location:
    East TN
    From my experience, to make them difficult to start.
    #16
  17. Benesesso

    Benesesso Long timer

    Joined:
    Jul 29, 2008
    Oddometer:
    9,898
    Location:
    West of Phoenix, Arizona
    Because that's ~ the normal 6V car voltage when the generator/voltage regulator is in "charge" of things.
    #17
  18. ttpete

    ttpete Rectum Non Bustibus

    Joined:
    May 13, 2009
    Oddometer:
    6,251
    Location:
    Dearborn, MI
    Ford put the ballast resistor in the wiring harness, and got the 12 volt starter boost at the starter relay.
    #18
  19. Wasser

    Wasser Spilt my beer

    Joined:
    Oct 31, 2009
    Oddometer:
    5,256
    Location:
    Colorado
    Yup and GM had the resistor in the starter solenoid. Terminal "R" to be exact.
    #19
  20. GreaseMonkey

    GreaseMonkey Preshrunk & Cottony

    Joined:
    Jun 16, 2006
    Oddometer:
    5,434
    Location:
    The only county in Illinois with no train tracks
    Geez there are a bunch of err, "mature" gentlemen on this forum!

    ...Because of course you'd diagnose the ballast resistor by the symptom that the car would start and it would immediately die when you released the key. IIRC it would be a $6-$9 repair including the part.
    #20