I promise this is my last question, at least on the dying problem. My wiring harness is missing the female end and the new distributor has a differnet color coded wires. So my question is if I can find a junk yard female plug I need to know which color to match up. My colors on the truck, Green, Blue and Gold (yellow?) and the color on the male end has Black, Black&purple, Black&red. Does anyone know what the three wires do? I know that Black is ground, but not sure if I need to match it with the Green? The wiring diagram in my Ford Book doesn't seem to match my set up either. Any guess on this? Thanks again I have really enjoyed everyones input. And I will be sending a picture file as soon as I get the larger memory card. So you all can see the phatom truck that works occassionally. ;-)

 

Hi, glad to hear that you are making progress. Per a 1975 shop manual, the two parallel blades of the dist connector is the pickup coil connections. The third contact is ground. The pickup coil should measure 400 to 800 ohms. Resistance from either side of the coil to ground must be greater then 70,000 ohms. I wouldn't worry about the wires color as long as the ground connection is correct. You could just cut off the connectors and use some insulated male and female spade connectors. Also you can test the pickup by dis-connecting the dist connector and connecting a dc voltmeter on the 2.5 v scale. Crank the engine; the meter needle should oscillate.

After reading between the lines in the description of the Durospark, I have reached the conculsion that it's main advantage over a points system is just getting rid of the points. I am more convinced that the MSD is a superior system. It sure made my 390 run better. Regards, Mike

 

More info, remember this is out of a 75 manual. You can check the resistance wire by the following test. Connect voltmeter to coil bat term and ground. Connect a jumper wire from coil DEC term to a good ground. Turn ign sw on, meter should read between 4.9 to 7.9 volts. If above 7.9 volts, the resistance wire should be replaced. Also manual shows dist wire colors as orange and purple for pickup coil, black for ground. If your resistance wire is bad, it would be the most likely cause for the hot wires. The coil is not supposed to operate at 12v.

 

Great info Mike!

Hi Colleen, I have a question. You say you have a blue wire, is it coming out of the module? If it is, I think you have the wrong year module, the blue wire was eliminated in ’76. How many wires are coming out of the module and what is the color of the strain relief where they all exit the module? Should be only six wires coming out of a blue strain relief. Also, what connector is missing?

Barry

 

>Great info Mike!
>
>Hi Colleen, I have a question. You say you have a blue
>wire, is it coming out of the module? If it is, I think you
>have the wrong year module, the blue wire was eliminated in
>’76. How many wires are coming out of the module and what
>is the color of the strain relief where they all exit the
>module? Should be only six wires coming out of a blue
>strain relief. Also, what connector is missing?
>
>Barry 
Barry, The blue wire I was talking about is the color that is running from the module to the coil. Blue wire is not coming out of the electric module. the module does have six wires and a Blue strain relief. I re-wired he distributor but had to guess on the wire set up. I am awsoming that the green wire running to the coil is my ground. the other wires I just guess at the matching set up. I hope I guess right. It does run, but will it continue to die? that is the guestion.
Barry where is the resistence wire your taking about in the coil? Is it internal in the coil itself? I only have three wires going to the coil, so not sure on how to check for a bad resistor. I did ohm out the coil and it was around 7.5 on a 10 volt scale. Which seems to fall in line with what you were saying.
I did notice that the wires coming off the electric module. the two wire connection has real big wires but where it connects to the truck the wires are half as big. Is that a problem. Thought the wire should be the same size. the four wires set up matches the four wires on the truck wiring. so I was just wandering if my was normal. Seems like you would want the same gauge wire on both ends. Of course I am no expert. Thanks again you all sure do make it eazier for me, at least I don't feel like I am doing this project alone. Just crossing my fingers and hoping the suber cab will running like the wind, without any unexpected stops along the way. Colleen

 

Hi Colleen: You just reminded me why I chucked the idea of retro-fitting the Durospark on older trucks and went with the MSD instead.

The resistance wire is between the ign switch and the coil bat terminal. A 76 module wiring hook up shows a red and a white wire going to the 2 prong plug. Green, orange, black, and purple go to the 4 prong. Green is the wire to the coil DEC terminal. Black goes to ground in the distributor. Orange and purple is the pickup coil. Don't worry about the different wire sizes. My manual only shows two wires to the coil. The extra wire may be for a tach.

 

Colleen, don't worry about the blue wire, it's not needed. Say I just threw together some stuff on the Duraspark in my gallery. Click on the '76 ignition wiring diagram, the pinouts and colors should be the same aside from that extra blue wire in your harness. It's a simplified drawing but may help, sometimes a picture is worth... well you know. Let me know if it makes any sense.

Barry

 

Sad news! We did not fix the problem, After replacing the dist. for the 2nd time, the truck died twice come home today, luckily it did restart. thanks for the information about diagram. I printed it out and will look at the resistance wire. We I drove the truck into work, the coil and Module where fire hot, so I witch out the two wires on the dist. as I didnt know other then ground which went where. Although the truck didn't die going to work but the coil/ module were extremely hot, The truck died twice after I change the wires, but the coil and module where not hot upon arrival at home. so I think I will take a closer look at the wiring diagram and replace the resitance wire now that I know where it is. Do you think I might have hurt the coil? Wish me luck, Husband says if I get it up a running I have to put a For Sale on it. Thanks Again, colleen

 

Sorry to hear that. Here's a quick way to check out that resistance wire. On the coil, connect a jumper wire from the DEC terminal to ground. Then take your voltmeter and connect one lead to the BAT terminal and the other lead to ground. Turn the ignition key to ON and read the voltage. If the reading is between 4.9 and 7.9 volts, it's ok. If it's higher, then it's the resistance wire.

Barry

 

Barry, what is the DEC terminal? And are you talking about it on the Coil too, I know where the BAT term is on the Coil just done where the DEC is. Also, what should the reading be with the engine running on the back of the coil. Before it goes through the coil. I am getting 9.5 volts at the back of the coil. As sooon as I figure where the DEC i will check for the resistence. Right now just checking the volts at the back of the coil with ign on It is reading 6.5 when running it goes up to the 9.5 volts. AGAIN this is at the back of coil. Thanks for the input.

 

Yes, the DEC terminal is on the coil too. It's the other small terminal and looks just like the BAT terminal. You want to ground-out the DEC terminal on the coil and read the voltage on the BAT terminal with the ignition key ON but the engine NOT running.

You can't troubleshoot or check voltages with the engine running on a Duraspark system, the readings will be misleading. You need a scope to do that.

Barry

 

Hey Barry, check the resistence wire as you describe. The reading after ground out the DEC was 11.14. So, I figure that the resistence wire is bad. You agree? Hey, do you think that if it is bad, and with the coil getting as hot as it was as well as the Electric Module that, that would have cause the dying problem? Have you ever swapped out the wires. Is it difficut? What do I need to do to replace the resistence wire and do you think that Auto zone will have it? It is raining here now, so I figure I have to change it later in the week. Any input on this would be greatly appreciated. Thanks again, not sure what I would have done without everyones input.

 

barry one other question Does the resistor wire do the same thing as a ballast Resistor if so could a wire one in instead of replacing the resistor wire? if so, any ideas on were to wire it in. does it have to be before the juntion on the start up passby? or would it not matter.

 

Yes, it sounds like your resistance wire is bad. With over 11 volts, no wonder your coil and module is getting hot. The module is probably the one dying from the heat, its not meant to carry that much current except when cranking.

The resistance wire does the same thing as a ballast resistor. You could run a ballast instead but it has to tap into the same place as the old resistance. This means before the starter bypass. If you go this route, ballast resistors get hot so it would have to be mounted somewhere safe like the firewall.

Now here is where I need everyone else's help. I have not torn into the resistance wire on these "late model" trucks. I know the earlier trucks much better. The resistance wire is under the dash in the wire loom with a bunch of other wires. It is green with a red stripe and should say resistance wire on it, should be fatter and more flexible than a regular wire. With yours carrying all that extra current, it might be darkened or even melted too. The problem when this wire gets hot is it also melts the adjacent wires in the harness. Hopefully yours is not that far gone.

The resistance wire originates somewhere near the ignition switch. On the older trucks it starts right out of the ignition switch but I'm not sure about yours. It is a few feet long and ends somewhere under the dash next to the firewall where it joins the starter bypass before going through the firewall into the engine compartment (I think, that's the way it is on the older ones, help me out guys). To replace the wire, you would need to cut it loose at both ends and splice in the new resistance wire. You can leave the old one in the harness as long as it hasn't damaged the other wires from frying.

If you want to run a ballast instead, it would splice into the same place. Just run regular wires from the two splice points and attach to the ballast. Not sure about Autozone but a good supplier should have the resistance wire. If you go the resistance wire route, don't cut it, it will change the resistance. Use the whole length they give you. This stuff is a bear to solder to, you might want to pick up some crimp-on barrel connectors or wire nuts to make the connections.

Raining huh? Boy we could sure use some of that down here in So.Cal!

Barry

 

Whoops! Sorry Colleen, the resistance wire is red with a green stripe.

I got mixed-up with someone else's advice for a green with a red stripe.

Barry