Driveability problem and mystery box

TomC750

TomC750

Senior Member
In chasing down a driveability problem I discovered that the ballast resistor in and out wires on the same post. I measured the resistance at one ohm. I have no idea why this was done and having zero knowledge of the car's history I have no one to ask. It did make me wonder however if the wicked spark I discovered at the plugs was such that the plug wires were leaking inside the conduits. (the coil has been rebuilt) At idle I have about 6 volts at the coil, on the road 8 volts. Not good. I will hook up the ballast wires correctly given that the resistor is not burned out.

Secondly I do not remember what the function of the box in the picture is. It is mounted on the dash side of the firewall.
 

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That "box" is the headlamp circuit breaker.
As you know, 6v. at the coil will hasten the life of your ignition points and coil.

The way it was wired allowed the full 6v. to get to the coil making starting a lot easier. That's fine if it's only temporary. There are ways to wire a switch in the circuit to allow6v. at start up. There is also a way to wire a diode in that automatically allows 6v at starting and drops to correct voltage once the engine is running.
 
Kube, Thanks for identifying the "box". After correctly connecting the ballast resistor, I measured (not running) voltage at the coil at 3.69 volts cold. I'll check it out on the road tomorrow. If I felt the need to provide full voltage when starting, I would connect a wire from the starter side of the solenoid to the coil, which makes sense to me without adding another component. More to follow...
 
TomC750 said:
Kube, Thanks for identifying the "box". After correctly connecting the ballast resistor, I measured (not running) voltage at the coil at 3.69 volts cold. I'll check it out on the road tomorrow. If I felt the need to provide full voltage when starting, I would connect a wire from the starter side of the solenoid to the coil, which makes sense to me without adding another component. More to follow...
Click to expand...
562930
 
TomC750 said:
Kube, Thanks for identifying the "box". After correctly connecting the ballast resistor, I measured (not running) voltage at the coil at 3.69 volts cold. I'll check it out on the road tomorrow. If I felt the need to provide full voltage when starting, I would connect a wire from the starter side of the solenoid to the coil, which makes sense to me without adding another component. More to follow...
Click to expand...

3.69v sounds healthy.
 
"If I felt the need to provide full voltage when starting, I would connect a wire from the starter side of the solenoid to the coil."


Then you would be feeding coil voltage to the starter when ever the switch was on.
 
Bob C said:
"If I felt the need to provide full voltage when starting, I would connect a wire from the starter side of the solenoid to the coil."


Then you would be feeding coil voltage to the starter when ever the switch was on.
Click to expand...


Bob, I think he knows the drill, and meant he'd use a temporary jumper wire.
 
I was not thinking about the diode, should have known better.

The car has an electric fuel pump, I had previously determined that the car ran no different with or without the electric pump. Yesterday I installed a separate switch for the pump in case it is needed or to prime the carb if the car sat for an extended time. It was wired to the ignition switch. Makes me wonder why one was installed. I drove the car a short distance with the gas cap loose and the air cleaner off, no change, it hesitates at a steady speed with a sharp random miss. Some times it will pull quite hard. It idles fine with no miss. The voltage at the coil at idle is 5.5 volts, at speed 6 volts. Seems high.

The dist was done by Charlie and the coil by Skip. It has a wicked spark that will jump almost an inch. I rebuilt the carb with no issues found. It was very clean and in good shape. Today I will recheck the float level with the carb on the car.
 
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TomC750 said:
I was not thinking about the diode, should have known better.

The car has an electric fuel pump, I had previously determined that the car ran no different with or without the electric pump. Yesterday I installed a separate switch for the pump in case it is needed or to prime the carb if the car sat for an extended time. It was wired to the ignition switch. Makes me wonder why one was installed. I drove the car a short distance with the gas cap loose and the air cleaner off, no change, it hesitates at a steady speed with a sharp random miss. Some times it will pull quite hard. It idles fine with no miss. The voltage at the coil at idle is 5.5 volts, at speed 6 volts. Seems high.

The dist was done by Charlie and the coil by Skip. It has a wicked spark that will jump almost an inch. I rebuilt the carb with no issues found. It was very clean and in good shape. Today I will recheck the float level with the carb on the car.
Click to expand...

With the ignition resistor wired in place, the voltage to the coil should be about half what you are experiencing. If you continue to run at or near 6v. points and coil will fail.
I saw in a previous post that once you had connected the resistor, the voltage did in fact drop.
Are you stating that now it is once again high? If that's the case, the resistor is most likely defective.
 
Kube said:
I saw in a previous post that once you had connected the resistor, the voltage did in fact drop.
Are you stating that now it is once again high? If that's the case, the resistor is most likely defective.
Click to expand...
A defective resistor would go open, less or no voltage getting through. Can't imagine how a resistor could become a solid conductor letting full voltage through. I suspect something else going on, something got mis-wired, providing full voltage to the coil.
 
Full voltage will show with the points open. The resistor drops the voltage only when the circuit is complete with points closed.
 
ford38v8 said:
Full voltage will show with the points open. The resistor drops the voltage only when the circuit is complete with points closed.
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Yes, but in post #9 he said: "The voltage at the coil at idle is 5.5 volts, at speed 6 volts. Seems high."
 
Kube said:
With the ignition resistor wired in place, the voltage to the coil should be about half what you are experiencing. If you continue to run at or near 6v. points and coil will fail.
I saw in a previous post that once you had connected the resistor, the voltage did in fact drop.
Are you stating that now it is once again high? If that's the case, the resistor is most likely defective.
Click to expand...
Kube, the voltage did indeed drop with the engine not running. Points were probably closed. Voltage is high running. I cannot imagine what could happen to any resistor let alone one with open coils to change resistance. The physical appearance is good. I will order another, not that expensive. I was a former electronics tech in a former life, but that was a long time ago. Appreciate the comment.
 
JayChicago said:
A defective resistor would go open, less or no voltage getting through. Can't imagine how a resistor could become a solid conductor letting full voltage through. I suspect something else going on, something got mis-wired, providing full voltage to the coil.
Click to expand...
True enough regarding a resistor failure. All the wiring appears totally stock, the only miswiring was with the resistor bypassed with both wires on the same post. So far a mystery for sure. I will sort it out eventually.
 
Tom, perhaps the low reading at idle is due to the generator not charging at that low RPM. Another factor to consider was the fuel pump connected to the ignition switch, which itself can pose a large resistance. For the above readings also, a digital voltmeter is useless while the engine is running, while an analog meter will give you good readings. Your erratic miss may be the coil overheating, and/or the condition of the ignition switch, or, and this is a biggie, your "wicked spark" is randomly finding ground: Inside your distributor would be a good place to look for evidence of that.
 
ford38v8 said:
Tom, perhaps the low reading at idle is due to the generator not charging at that low RPM. Another factor to consider was the fuel pump connected to the ignition switch, which itself can pose a large resistance. For the above readings also, a digital voltmeter is useless while the engine is running, while an analog meter will give you good readings. Your erratic miss may be the coil overheating, and/or the condition of the ignition switch, or, and this is a biggie, your "wicked spark" is randomly finding ground: Inside your distributor would be a good place to look for evidence of that.
Click to expand...
My readings were independent of the electric fuel pump. And true, the ammeter showed no charge at idle, normal. Yes, a digital ammeter gets confused if using in such a manner. I use a good analog one. The ignition switch seems perfect, I checked it every way I could. The wicked spark I mentioned is when I pull the plug wire off and hold it back from the plug. It is strong and blue. I considered that it may find ground inside the conduits. You did give me an idea however, I think I will disconnect the generator and take it for a ride. That is if it would stop raining!
Thanks 38fordv8
 
Somewhere on the Barn there is a wiring diagram with a diode in it . To do what you want.

Goes from the solenoid to the coil, only activated when starting.
 
slowforty said:
Somewhere on the Barn there is a wiring diagram with a diode in it . To do what you want.

Goes from the solenoid to the coil, only activated when starting.
Click to expand...

Here is your somewhere. RIP Bob Shellady AKA Supereal

"Thanks for posting my original "quick start" page. The purpose of the circuit is to compensate for draw down on the battery from the starter motor during cranking.
Any "top hat" diode will work, as it just augments the coil voltage until the engine starts,
using low current. Be sure to install the diode as shown to prevent energizing the coil after starting. Polarity is important. If "backward" the engine will start without turning on the ignition. Just reverse the connections to the diode."
 

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