Announcement

Collapse
No announcement yet.

Ignition Voltage Question

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Ignition: Ignition Voltage Question

    My 283 powered 1965 Daytona started running rough and now is nearly impossible to start. I recently replaced the fuel pump and checked it, 5.0 PSI so we're OK there. The previous owner added a 30A fuse between the starter and the switch to protect against melt downs when the ignition switch fall out and it did once, I'm glad it was there. It had household wire nuts on the splices and was not even taped. We soldered and shrink tubed the joints and eliminated that from the equation. The battery was at 12.86 VDC across the posts and 11.56 at the coil to ground with the ignition switch in the "on" position. We unwrapped the wire harness in the ignition area and all looked OK and the ballast resistance wire is in tact. So why the high voltage at the coil? Shouldn't it be more like 9 VDC through the ballast wire? We will pull the distributor this weekend and check the points, I suspect they're fried and screwing up the dwell. Any thoughts? My first thought is to pull the ignition switch, (dreading the thought of that), and replacing the wire with the proper gauge standard wire. I would then go to a traditional ceramic ballast resistor on the firewall and then to the coil. This way if I got to HEI or other type ignition that needs 12 VDC it's right there, just bypass the resistor.

    JK

  • #2
    The voltage you see at the coil (+) terminal depends upon whether the points are closed or open. Resistance wire, and resistors in general do not drop voltage if there is no current flowing. 11.56 volts tells me the points are open, and there is a little voltage drop between the battery and the ignition switch, due to other small loads on the circuit, such as the instruments.

    Ignition switch falling out is a sign that the bayonet lugs of the chrome bezel are shot. The vendors sell a new and improved aluminum bezel with tougher bayonet lugs that will fix that.

    Suggest you get the engine started, and put a dwell meter on it. Dwell should be 30 degrees. Any large variance from that will cause starting problems and poor performance.
    Gord Richmond, within Weasel range of the Alberta Badlands

    Comment


    • #3
      I measured the resistance of the pink resistor wire in my car and it wasn't even worth calling it a resistor wire. Why not just put an HEI in it? It'll drop into the 283. You can get a new one ready to install, with coil ,cap, and rotor for around $50 0n ebay. You'll just need different plug wires, another $20, and a female spade lug for the power wire. I put one in my Stude 289, ( with modification) and just used the pink "resistor" wire for power to it. It's been working fine for five years now.
      sigpic

      Comment


      • #4
        As Gordon said. It is not just the resistance of the resistance wire that determines the voltage to the coil. If the coil has 2 ohms resistance and the coil primary has 2 ohms resistance the coil will receive 6 volts from a 12 volt system. Same 12 volt system but with a 1 ohm coil and a 2 ohm wire; the coil will receive 6.666666 volts The other 3.3333 Volts will be turned to heat in the resistance wire.
        Ron

        Comment


        • #5
          The switch falling out was fixed a long time ago so that is no worry. I have a "Maxx" brand electronic distributor I can put in. I'll check out more about what the condition is of the distributor that is in it before swapping . I had new "Delco" points, cap and rotor put in last summer when it had a valve job. I may not have the right plugs or wires on it for a "points" distributor, I'll check that out also. Thanks for the info.

          JK

          Comment


          • #6
            If you turn the switch on and check voltage at the coil you ought to see 12+ volts. When you start the car current will flow thru the resistor wire to the coil and the voltage measured at the coit should be 6 or 7 volts. This is to try to prevent early point burn out with the higher voltage. (just looked at the fine print on my new Delco Plugs---China. I don't think I'd change the distributor. Last I checked, you can't buy a resistor wire--and they fail fairly often. If bad, just replace with an ign resistor

            Comment


            • #7
              Crank circuit = 12v no matter what (on a 12v system).
              Run circuit = 12v with internal resistor coil .
              Run circuit = 7 volts with an external ballast resistor and standard coil (or resistor wire)(or point burn will occur) .
              Note: You could run a 6v coil with 12v if you run a ballast resistor.
              Note: If your engine cuts off.... Grab the coil with your bare hand.
              If it is too hot to hang on to, you have (a) a bad coil, or (b) you need a ballast resistor and your points are probably blue.
              HTIH (Hope The Info Helps)
              Jeff

              HTIH (Hope The Info Helps)

              Jeff


              Get your facts first, and then you can distort them as much as you please. Mark Twain



              Note: SDC# 070190 (and earlier...)

              Comment


              • #8
                Originally posted by bensherb View Post
                I measured the resistance of the pink resistor wire in my car and it wasn't even worth calling it a resistor wire. Why not just put an HEI in it? It'll drop into the 283. You can get a new one ready to install, with coil ,cap, and rotor for around $50 0n ebay. You'll just need different plug wires, another $20, and a female spade lug for the power wire. I put one in my Stude 289, ( with modification) and just used the pink "resistor" wire for power to it. It's been working fine for five years now.
                A HEI will fit the engine but may not fit the intake. Some older intakes interfere with the HEI distributor body. The resistor should be about .7 ohms (not much) running voltage should be 9.8 to 10.2 volts. starting voltage should be battery voltage due to the resistor bypass built into the starter solenoid. There is one on an older GM starter just like the bypass terminal on a fender mounted solenoid. If the bypass wire is broke or disconnected, the engine will start hard or not at all.
                james r pepper

                Comment

                Working...
                X