Ford Muscle Cars Tech Forum banner

81 - 88 of 88 Posts

·
Registered
Joined
·
70 Posts
165864
165865
More follow up on running my bypass wire in my 66 LTD. So far, the car is still running much better since I choose to run the bypass wire. So well, that I decided to run a bypass wire in my 66 Mustang 6 cyl convertible, which had been running the Pertronix 1 unit and stock coil since 2011, off the resistor wire. I always thought maybe there was something just not right with the Mustang, but it was so minor, that I left it alone for almost ten years now.

I decided to do the same, disconnect the bypass wire at the ignition, run the bypass wire through the firewall and to the coil. I also upgraded the 6 cyl Mustang to a 3 ohm Flamethrower coil, per the Pertronix help line, they said that the coil would run cooler with that 3 ohm Flamethrower. So far, so good with the Mustang also, it does seem to run better with the bypass wire.

I painted up both new Flamethrower coils, to give them a sort of stock look, with the yellow top, and got the Autolite coil decal, which may not even be technically correct, as I think a late 65 or early 66 coil would have had a FoMoCo stamping, but since they dont have that decal yet, this one will do.

I also show a picture here where I ran my bypass wire, so future people can get an idea of how I tackled getting mine through the firewall, in my case, at the hose that goes through the firewall off the mainfold and connects to my vacuum actuated switch inside the car to open the rear vents. The Mustang was a similar situation, I had a non used firewall plug that I drilled through and snaked the wire through that into the car and then the bypassed resistor wire.

One more strange thing. I was going to, for just visual purposes, going to hook back up the now disconnected old coil positive lead to the coil positive terminal, instead of letting it dangle there. For shows and such, it just looks better that it is connected to something instead of sitting there unused. I thought by disconnecting the resistor wire inside the car off the ignition switch would ultimately render that wire now non voltage carrying.

To my surprise, when I hooked up a multimeter to it, on both cars, after all the work was done, I am still getting a 1 volt reading coming through that wire, even though it is no longer connected to the resistor wire that it would go to through the firewall.

Is that just residual voltage coming from some part of the system. Seems strange that something disconnected can still have one volt of current going through it. I choose to leave it disconnected in the engine bay instead of letting it sit on the positive coil terminal, but I dont understand why it has current going to it when it was clearly disconnected at the pink bypass wire inside the car.
 

·
Registered
63 convertable
Joined
·
651 Posts
first, the resister wire is inside the car only. the wire in the engine bay is just copper wire. next there is no 1volt of current. if you are reading one volt you don't know the current unless you know the resistance. a wire in close proxcimity to an other wire with current flowwing in it, a voltage will be induced into the non powered wire. usually not much current is involved in the non powered wire
 

·
Registered
Joined
·
70 Posts
I think I understand, extech, what you are saying. I know the resistor wire is in the car, but it does ultimately go to the wire harness plug inside the car at the firewall, and goes back from a pink to a Red/Green wire as it comes out the other side of the firewall, on the engine side, and then to the positive of the coil.

It reads like what you are saying that the 1 volt reading I am getting at the now disconnected Red/Green coil wire is just residual voltage due to the proximiity of the other wires that still have voltage coming through them, it is just picking up a small amount due to conductivity properties of the wire.

Would it be "safe", for appearance purposes, to hook the red/green coil positive connector back to the coil positive terminal, just so it isnt dangling there, since it in theory is no longer getting any juice from the unplugged resistor wire?
 

·
Registered
63 convertable
Joined
·
651 Posts
is the end of the resistor wire insulated? once you connect it to the coil the resistor wire will be hot.
what i was getting at was you could have replaced the resistor wire up to the firewall in side the car , leaving the outside wire to the coil alone. btw voltage does not travel or even move. it is the force that causes current to flow
 

·
Registered
Joined
·
70 Posts
Thank you for the clarity ex tech.

I see what your saying now. Looking at it in reverse, if I connect it at the coil positive, the current will now flow back into the car, to the resistor wire and to the end of the bullet plug where I took it off at the igntion switch. If I dont have that insulated someway, then if that end of the resistor wire, which is now dangling on the inside of the car under the igition switch touches metal, I could have a big issue. Make sense.

I will just put that coil plug on at shows then in the engine bay, for appearance sake, and when driving all the other times, totally leave it off the coil, to avoid any issues inside the car.

Electrical is not my thing, but I am good enough to be able to use a multimeter for voltage readings and to test a coil for ohms. I just assumed that getting a 1 volt reading from a disconnected wire meant that 1 volt of current was being pulled from somewhere to cause that reading on a disconnected wire. I guess the wires being in close proximity when the car is running causes some voltage reading to be displayed on that disconnected wire. I didnt know that could happen.
 

·
Registered
Joined
·
292 Posts
Yep, it's called crosstalk. A big deal in parallel communications, e.g. old parallel printers, or SCSI cables for computers. Sending a pulse down one wire can easily induce a current in a nearby wire, so a lot of detail is spent on properly shielding the data wires from one another. It applies to our engines, too. The spark plug cables shouldn't have long, parallel runs, particularly #7 and #8, which are next to one another in the firing order, and the cylinder head. They need to cross at least once between the distributor and plugs.

Pat
 

·
Registered
63 convertable
Joined
·
651 Posts
in newer vehicles, the o2 sensor only work s on up to 1 volt. having ... say an amplifier power lead be next to an o2 sensor lead can make the computer do some wierd and unwanted stuff
 
81 - 88 of 88 Posts
Top