TurboType1
Active Member
Is it OK to run the electric choke off the Coil + ? I've already done away with the Ballast resistor for MSD Drop-in distributor.
Thanks...Pete
Thanks...Pete
Electric choke
- Thread starter TurboType1
- Start date
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67Dart273
Well-Known Member
Yes but do yourself a favor first. If you are using stock wiring and the factory bulkhead connector, check the harness for "voltage drop."
Turn the key to "run", engine OFF
Put one probe of your meter on the battery POS post. Stick the other probe on the IGN feed, IE where you got rid of the resistor. You are looking for a VERY low reading, anything over .2V means you should look things over, .3V or more (that's three TENTHS of a volt) get more serious
Your suspects are the bulkhead connector, the ignition switch connector, and the switch itself.
If you have significant drop, it will cause overcharging. If you can't find it and don't want to mess with it, add a relay triggered off the original "ign run" wire to key the relay, and run the ignition/ choke/ and alternator field/ regulator off that
Turn the key to "run", engine OFF
Put one probe of your meter on the battery POS post. Stick the other probe on the IGN feed, IE where you got rid of the resistor. You are looking for a VERY low reading, anything over .2V means you should look things over, .3V or more (that's three TENTHS of a volt) get more serious
Your suspects are the bulkhead connector, the ignition switch connector, and the switch itself.
If you have significant drop, it will cause overcharging. If you can't find it and don't want to mess with it, add a relay triggered off the original "ign run" wire to key the relay, and run the ignition/ choke/ and alternator field/ regulator off that
TurboType1
Active Member
Thanks for your reply. I kinda thought that would be OK to do.
Forgive my ignorance, but , if I put one probe on the POS terminal and the other on ing feed , how will the meter read anything? Shouldn't one probe go to ground? Not sure I get that...although I definitely understand the importance of looking for Voltage drop.
Thankx again....Pete
Forgive my ignorance, but , if I put one probe on the POS terminal and the other on ing feed , how will the meter read anything? Shouldn't one probe go to ground? Not sure I get that...although I definitely understand the importance of looking for Voltage drop.
Thankx again....Pete
Lonewolf3165
Living the Dream!
You are reading the voltage drop across the positive side of the circuit. Voltage is the potential of the circuit. If there is any loss(high resistance- bad connection) it will show up on the meter. Just like checking a bad ground, you would check between the ground on a component & the negative battery terminal for excess drop.
kt340sport
Well-Known Member
They want you to run it to the fuse box , i know my edelbrock said not to run from coil, or ballist.
67Dart273
Well-Known Member
Here is what you are checking:
The circuit path for your ignition feed is
The battery -- fuse link -- through the bulkhead connector -- ignition switch connector -- through the switch -- back out the switch connector on the ignition "run" or "dark blue" -- back OUT the bulkhead connector -- to the ignition system, the alternator field, the regulator, and the electric choke if used
Every connection I mentioned, especially the bulkhead connector (twice) and the ignition switch connector (twice) can be a poor connection and lose a tiny (or large!!) amount of voltage when supplying the load (ignition system.) The switch contacts inside the switch can get "poor" and lose some.
If you have a "near perfect" circuit, there WILL NOT BE measurable voltage drop, and by "near perfect, I mean nice big wires, better connections everywhere, etc.
That's why you are talking in tenths of volts. MANY of these old cars are far worse. I've helped a few guys on here, and my own 67, before I fixed it, had ONE VOLT drop in this circuit.
The circuit path for your ignition feed is
The battery -- fuse link -- through the bulkhead connector -- ignition switch connector -- through the switch -- back out the switch connector on the ignition "run" or "dark blue" -- back OUT the bulkhead connector -- to the ignition system, the alternator field, the regulator, and the electric choke if used
Every connection I mentioned, especially the bulkhead connector (twice) and the ignition switch connector (twice) can be a poor connection and lose a tiny (or large!!) amount of voltage when supplying the load (ignition system.) The switch contacts inside the switch can get "poor" and lose some.
If you have a "near perfect" circuit, there WILL NOT BE measurable voltage drop, and by "near perfect, I mean nice big wires, better connections everywhere, etc.
That's why you are talking in tenths of volts. MANY of these old cars are far worse. I've helped a few guys on here, and my own 67, before I fixed it, had ONE VOLT drop in this circuit.
I run my electric choke from a relay that is triggered by ignition circuit, a method recommended by Holley.
Before making this modification, the choke and coil acted as two resistances in parallel that the coil saw as a voltage drop. Result was poor idle, and lower secondary voltage to the plugs.
Before making this modification, the choke and coil acted as two resistances in parallel that the coil saw as a voltage drop. Result was poor idle, and lower secondary voltage to the plugs.
TurboType1
Active Member
I do get the importance of checking for voltage loss/drop and it is a must do.
But are we talking using a volt meter or Ohm meter? Because using a voltage meter wouldn't you have to have one probe on the negative in order for it to read anything when probing a positive? I mean checking a battery you put one on positive and the other on the negative..Right? If you put them both on the positive you'll get nuttin..unless there is something I haven't learned yet .
My .02...Pete
But are we talking using a volt meter or Ohm meter? Because using a voltage meter wouldn't you have to have one probe on the negative in order for it to read anything when probing a positive? I mean checking a battery you put one on positive and the other on the negative..Right? If you put them both on the positive you'll get nuttin..unless there is something I haven't learned yet .
My .02...Pete
67Dart273
Well-Known Member
NOpe. You are measuring voltage from one end of the harness to the other.
Let's talk about this a DIFFERENT way. Let's say there is 1/2 volt lost (figure out of the air) in the harness.
So if you were to turn the key to "run" and measure the battery, let's say the battery -- at the posts -- measured 12.6V.
Let's say you now move the positive probe over to the ignition run buss on the firewall, and you measure 12.1, which corresponds to our "1/2 volt drop" we picked out of the sky for example.
In the above test, you keep the second meter lead grounded to the battery neg. post.
THIS 1/2 VOLT is being lost IN THAT HARNESS, in that circuit path I mentioned.
So you can measure that drop DIRECTLY by putting one probe on the battery pos. (the source) and the other probe out where the IGN system connects (the load) and you will then measure the 1/2 volt directly.
THIS ASSUMES that you have no drop in the ground circuit.
Voltage drop gets WORSE with more CURRENT
Let's say you had a trunk mount battery. If you extended your test leads, and you clipped one meter lead to battery positive, and brought the meter up and clipped the other lead to the starter stud, then went in and turned on some accessories, heater, lights, or cooling fans, electric pump, and the ignition.
You might measure a tiny drop with a nice big cable, or NOTHING because you aren't drawing all that much current, and you are using HUGE cable. (There will BE some drop, your meter might not be sensitive enough to measure it)
BUT if you were to disable the IGN so you can crank the car, you might measure a few tenths of a volt in this setup.
THE POINT is that WITH ENOUGH CURRENT even a huge battery cable can exhibit voltage drop.
You can check lots of things this way. Let's say you suspect a bad battery connector or bad cable. Disable the IGN so you can crank the engine and load the cable.
Put your meter probes -- one on battery post, other probe on battery clamp, and crank the engine. The meter will show you how much loss there is IN THE CONNECTION ITSELF
IF you suspect a bad cable, "stab" your probes on the battery CLAMP (not the post) and at the other end of the cable stab your probe into the END CONNECTOR on the cable, NOT the stud it fastens to
The meter reading, while cranking, will give you an idea of how good/ bad the cable is.
Some years ago, on my old Ranger, the ground battery cable went down to the frame, had an "inline" connector which bonded the cable to the frame, then continued on and jumpered over to the engine block.
I was having trouble starting, but the lights were nice and bright. The cable had corroded AFTER the ground tab on the frame, so the engine block was not seeing a good ground.
Only took about 10 minutes of head scratching and a meter to figure that ground HAD TO be bad.
Hope this helps
Let's talk about this a DIFFERENT way. Let's say there is 1/2 volt lost (figure out of the air) in the harness.
So if you were to turn the key to "run" and measure the battery, let's say the battery -- at the posts -- measured 12.6V.
Let's say you now move the positive probe over to the ignition run buss on the firewall, and you measure 12.1, which corresponds to our "1/2 volt drop" we picked out of the sky for example.
In the above test, you keep the second meter lead grounded to the battery neg. post.
THIS 1/2 VOLT is being lost IN THAT HARNESS, in that circuit path I mentioned.
So you can measure that drop DIRECTLY by putting one probe on the battery pos. (the source) and the other probe out where the IGN system connects (the load) and you will then measure the 1/2 volt directly.
THIS ASSUMES that you have no drop in the ground circuit.
Voltage drop gets WORSE with more CURRENT
Let's say you had a trunk mount battery. If you extended your test leads, and you clipped one meter lead to battery positive, and brought the meter up and clipped the other lead to the starter stud, then went in and turned on some accessories, heater, lights, or cooling fans, electric pump, and the ignition.
You might measure a tiny drop with a nice big cable, or NOTHING because you aren't drawing all that much current, and you are using HUGE cable. (There will BE some drop, your meter might not be sensitive enough to measure it)
BUT if you were to disable the IGN so you can crank the car, you might measure a few tenths of a volt in this setup.
THE POINT is that WITH ENOUGH CURRENT even a huge battery cable can exhibit voltage drop.
You can check lots of things this way. Let's say you suspect a bad battery connector or bad cable. Disable the IGN so you can crank the engine and load the cable.
Put your meter probes -- one on battery post, other probe on battery clamp, and crank the engine. The meter will show you how much loss there is IN THE CONNECTION ITSELF
IF you suspect a bad cable, "stab" your probes on the battery CLAMP (not the post) and at the other end of the cable stab your probe into the END CONNECTOR on the cable, NOT the stud it fastens to
The meter reading, while cranking, will give you an idea of how good/ bad the cable is.
Some years ago, on my old Ranger, the ground battery cable went down to the frame, had an "inline" connector which bonded the cable to the frame, then continued on and jumpered over to the engine block.
I was having trouble starting, but the lights were nice and bright. The cable had corroded AFTER the ground tab on the frame, so the engine block was not seeing a good ground.
Only took about 10 minutes of head scratching and a meter to figure that ground HAD TO be bad.
Hope this helps
TurboType1
Active Member
Now I get it... Thanx
This car is in the final stages of assembly,but doesn't have an actual battery in it with all the associated grounds. I have been testing circuits with a booster pak up to this point.
All harnesses are new including the bulkhead terminals so I guess I will wait for the battery to get serious
Thanks again...Pete
This car is in the final stages of assembly,but doesn't have an actual battery in it with all the associated grounds. I have been testing circuits with a booster pak up to this point.
All harnesses are new including the bulkhead terminals so I guess I will wait for the battery to get serious
Thanks again...Pete
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