Voltage to coil

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jlindemann

jlindemann

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I am hoping this is a quick one for someone. I am having issues getting my car to start up. It is a '64 Barracuda with a 318 in it. I believe it is the factory coil that was on the motor when the previous owner put it in. When I check the voltage on the resistor on the firewall, I get 11.6 on the top and only 4.6 on the bottom. This means that I am only getting 4.6 to the + side of the coil. If I bypass the resistor and tie the two lines that go to the resistor together, she turns over on the slightest turn. I know I need more volts to the coil and have already bought a new resistor from the local Bumper to Bumper and got the same readings. Now I am at a loss!? Any ideas or suggestions?
 
On the ballast resistor there should be 3 wires. 1 on one side, and 2 on the side going to the coil.

The 2 on the side to the coil is 1 feed that is regulated by the resistor, the other is a bypass feed from the ignition switch. The bypass feed bypasses the resistor during start mode and you get full battery voltage (or 9 to 11 in start mode) to the coil.

I'd check for full voltage to the coil in START mode. That bypass feed doesn't have to be on the resistor, it can be on the coil.
 
The above is correct, and if you are trying to start the car by jumpering the start relay or the starter solenoid, that bypass circuit does not get engages.

The "bypass" voltage, on the brown, going to the coil side of the ballast, is the bypass coming from the ignition switch through the bulkhead.

I would also check out the path for the "ignition run" (dark blue, also known as "ignition 1") You say it is 11.6. WHAT IS the battery voltage?

Do this:

With key in "run" engine off, and make sure points are closed---look for a low reading at coil as opposed to "same as battery."

Now with the points closed, put one meter probe on the battery and the other on the key side of the ballast.

You should have no more than 1/2 volt, and that is generous. Less is better.

The other thing a voltage drop causes at the ignition switch side of the ballast is OVERCHARGING, because this is the supply and "sense" for the regulator. If this voltage is dropped through the harness/ bulkhead from the battery, the regulator simply ramps up the alternator to compensate.

Before I (just got it running) rewired my 67, there was a ONE VOLT drop through the bulkhead/ harness. The system was charging at more than 15 volts
 
I am at work right now so I can't give you details but if I remember correctly there are two wires on the top and two wires on the bottom of the resistor. Could that be my issue? I will try to look and determine wire colors tonight when I get home and post them for your help. Thanks for the help!
 
It is only a 2 post resistor. I believe everything is stock our at least that is the way it appears. I can try to post pics when I get home tonight. There are trip wires tied together on one female fitting on both terminals of the resistor
 
67Dart273 said:
Wait a minute----You have a 2 or 4 terminal resistor?

What kind of ignition system we working with here?
Click to expand...

What is the difference between the 2 and 4 terminal resistor? I'm pretty sure i have a 4 terminal resistor on a electronic ignition distributor with an orange ignition box. Is that not correct? Not trying to hack the tread, I'm in the same boat, just trying to find out if I have a faulty coil.
 
jlindemann said:
It is only a 2 post resistor. I believe everything is stock our at least that is the way it appears. I can try to post pics when I get home tonight. There are trip wires tied together on one female fitting on both terminals of the resistor
Click to expand...

It probably only has three, unless they used that as a junction for the regulator

One side should have "dark blue" the "run" voltage from the key. This may have a wire taking off to the regulator

Coil side should have two, one goes to coil positive, other one is normally brown. This is the ignition bypass voltage from the key in "start."






slant6/4speed said:
2 terminal is for points "dizzy" and a 4 terminal is for electronic "dizzys". What year is the 318?
Click to expand...

Not always true. The so called older "5 pin" ecu MUST use a 4 pin resistor, but the newer "4 pin" ECU CAN USE either 2 or 4 pin resistor


67cuda360 said:
What is the difference between the 2 and 4 terminal resistor? I'm pretty sure i have a 4 terminal resistor on a electronic ignition distributor with an orange ignition box. Is that not correct? Not trying to hack the tread, I'm in the same boat, just trying to find out if I have a faulty coil.
Click to expand...

See answer above. You really should start your own thread.
 
OK, back home, here is what I have. On the top post I have 2 dark blue wires. One looks like it is coming from the Ign. box on the firewall. The other one is coming from the big block of wires (sorry for the technical term). Then on the bottom post I have a brown wire, which also goes back to the big block on the firewall and then the wire going to the coil. Should also add that a wire is running from the positive side of the coil to the electric choke. Not sure if that matters at all.

Update: battery has 12.58 volts. Tested both dark blue wires with the key turned to ON position. One had no voltage, the other had 11.78. I connected the one that had voltage and reconnected the brown wire and the wire going to the coil. Still only got 4.67 volts on both the coil side wires.
 
Sounds normal. The dark blue going to the "big block" is the firewall connector going through the firewall. This is a source of trouble, as those contacts become burned and corroded

The brown wire is the "ignition bypass" coming from the ignition switch. This powers the coil directly when cranking the engine.

The "box" you refer to is probably the regulator. Should have two wires, a dark green to a screw terminal, and a dark blue to a "push on" terminal
 
You are right on the 'box', it says IGN and FLD. Two wires, one a push on the other a screw terminal.

So what sounds normal, the wire configuration or the voltage?

What is the easiest way to check the connections in that block? Do they come out easy?
 
I connected the one that had voltage and reconnected the brown wire and the wire going to the coil. Still only got 4.67 volts on both the coil side wires.
Click to expand...

Now, check the voltage to the coil with the key in the "START" position.
 
OK, so I started from square one. Pulled the dark blue line that didn't have voltage and pulled all plugs off the coil side and turned the key on. Got about 12 volts on both sides of the resistor. So then I connected up the brown wire and it stayed at 12 volts on both sides. I then added the wire that goes to the coil and it dropped down to 4.6 volts on the coil side and 11.4 on the other. I then removed the wire that went from the + post on the coil to the electric choke and the voltage went up to about 5.3. I am not sure if that is telling me everything is OK? My son just went to bed, so I can't crank it over to see if it starts up right away or struggles like it has in the past?
 
We'll just have to see what it does in crank mode later on. You could pull the wire on the starter solenoid to keep it from engaging; then with the key in START position you'll be able to see if the bypass wire gives the 12 or so volts on the load side of the resistor.
 
greg r said:
We'll just have to see what it does in crank mode later on. You could pull the wire on the starter solenoid to keep it from engaging; then with the key in START position you'll be able to see if the bypass wire gives the 12 or so volts on the load side of the resistor.
Click to expand...

You don't want to do that, because you want to measure this under "real" conditions. You want to measure with the system loaded, just as it would be starting


jlindemann said:
OK, so I started from square one. Pulled the dark blue line that didn't have voltage and pulled all plugs off the coil side and turned the key on. Got about 12 volts on both sides of the resistor. So then I connected up the brown wire and it stayed at 12 volts on both sides. I then added the wire that goes to the coil and it dropped down to 4.6 volts on the coil side and 11.4 on the other. I then removed the wire that went from the + post on the coil to the electric choke and the voltage went up to about 5.3. I am not sure if that is telling me everything is OK? My son just went to bed, so I can't crank it over to see if it starts up right away or struggles like it has in the past?
Click to expand...

What you described shows it's wired OK, but you ARE in fact getting a lot of drop through the harness. 11.4 is nearly a ONE volt drop from the battery. Too much. You need to chase this down. See if you can get your meter on the back of the ignition switch, and/ or on the interior side of the bulkhead where the blue wire comes through.

You have wiring diagrams?

It is important to measure with the ignition all hooked up, because this 'loads' that circuit. If you unhook all loads, you remove the voltage drop, and it will measure "same as battery."

You want to check your ignition bypass under "real" conditions with the starter cranking.

Remove the coil wire, and hook it to ground

"Rig" your meter so you can see it when operating the key, one probe clipped to battery positive, the other clipped to the coil side of the ballast. Make sure, as I mentioned, that the ignition is all hooked up.

Now crank the engine using the key, and see what the meter reads. You are measuring "voltage drop" from the battery--through fuse link, through bulkhead connector, through ammeter circuit, through ignition switch connector, through the switch and back out the connector, BACK through the bulkhead connector (on the brown wire) and to the coil.

You are looking for a low reading, the lower the better, more than 1/2 volt is too much and shows a problem in the above path somewhere.

Finally, a rough check of your battery starter condition can be made by measuring right at the battery while cranking. Absolute "low" end is 10.5V. If the battery reads that low, either the battery is discharged or in poor shape, or the starter is drawing way too much current.
 
OK, I will give that stuff a try in a few days. I have a bachelor party to go to for a friend today, so no working on the car today and probably be too hung over tomorrow! :eek:ccasion:

I will keep you posted on what I am finding. Thanks again for all the help, it is greatly appreciated.
 
But if I put just the one dark blue wire and the brown wire on the resistor and still got 12 volts, doesn't that tell me that I am not losing the voltage in the block or on the ignition? Is the coil pulling too much? I thought maybe it was because we had hooked up the electric choke to the coil, but that only made the coil side go from 4 something to 5 something.
 
The thing you must realize is that RESISTANCE such as a "bad connection" such as corroded contacts in the bulkhead connector, do not show up as lower voltage UNTIL you start to hook things up which DRAW CURRENT. These things include the ignition system (with points closed) the choke, and the regulator field circuit.

If you unhook everything from the blue wire, and just measure it with "no load" the meter itself draws a TINY, insignificant amount of current, so the meter does not draw down the voltage. Therefore with no load connected, you will "think" you have a good circuit.
 
OK, so tonight in the humid weather of Wisconsin, the wife gave me a few minutes to work on the car. I disconnected the 2nd blue wire to the resistor and removed the choke wire from the coil. Pumped the pedal a few times and she almost turned over. Pumped a few more times and she turned over. Because the choke didn't have any power, she idled pretty rough, but once the engine was warm I shut it off and turned the key again and it started right up.

I am guessing that hooking that choke wire to the positive side of the coil wasn't the right thing to do. Can anyone give me a suggestion of where I can pull power from for the choke?
 
Somehow here we are having a massive "disconnect." The choke should NOT hook to the + side of the coil, but to the OTHER side of the ballast, the KEY side, the side where the "dark blue" run wire hooks.

However, IF you have a voltage drop problem AT THAT POINT, you need to work on fixing that problem.
 
So just to confirm, on the ballist/resistor, I should have the dark blue wire and the choke wire on one side, then the brown wire and the positive coil wire on the other side.
 
Thanks for all the help, that worked great. Pumped the pedal about 6 times and she started right up, well died the first time but that was because I let off the gas. Still have to figure out how to set the choke though to help it run a bit better right out of the gate. Guessing I will just have to mess around with it. Now I just need to figure out what that other dark blue wire goes to.

Also noticed that I had a bit of fuel around the top gasket of the carb? I just had it professionally rebuilt, so not sure where it would be coming from. Checked all the screws and they all seemed to pretty snug.
 
You need to check all your grounds first. ALL! Then check all the lead wires ( off the battery ). If that oesn't work pm slantsixdan.He's an electrical genius.
 
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