Howdy! Just trying to get my old 1974 Ford F-250 2wd with a 390 ci V8 and an automatic back up and running. Got the truck almost 10 years ago and had gotten it to run great at that time. Unfortunately, right after I got it going a damn pack rat got in it and ate all the wiring in the engine compartment and some under the dash. I got a cab from a buddy from a '76 F-150 with a good harness but long story short the truck got tucked away in the back of one of our sheds with the extra cab sitting on the flat bed and there it's sat.

Well the time has finally come for me to get the truck back out and get it on the road again! So far I've removed all the old '74 harness and got most of the '76 harness installed. After doing some checking I found out the '76 harness is used
With the duraspark ignition so I went ahead and got a '76 distributor to match the wiring harness. I also mounted the ignition control module in the correct location on the fender. Everything is good up to this point but this is where I start to have a few questions.

First, with my new harness by the distributor, I have three connectors coming from the harness with it laid out towards the front of the engine. First, is a circular connector that accepts three prongs which goes to the distributor. Second is the flat three prong connector that I believe goes to the coil, temp. sensor, and oil pressure. And I have a third connector, this is where I get confused. The third connector accepts four prongs but I am unsure what this is supposed to go to. Is this for some sort of emissions pieces I don't have and can I just leave it disconnected? Or am I missing something else from the wiring harness?

All three connectors:



Connector I'm not sure what it goes to (it's the connector to the right in the picture above):


I still have the original '74 wiring that lays along the top of the left hand valve cover) with the flat connector that goes to the coil, oil pressure sender, and temp. sender. Will I be okay hooking this original '74 section of the harness to the new '76 harness or has any of that wiring changed?

Finally, my '74 has the original dual tanks with the tank selector on the dash to switch between the tanks to get the fuel level readings. My original connectors on the '74 harness were taken out by the pack rat. I'm just needing to clarify that this connector on the '76 harness does run to each fuel tank sender.

Connector in question for the fuel tanks:



Sorry for all the questions, I'm a Jeep guy so all this Ford specific stuff is fairly new to me. Thanks for the help!

 

The first one appears to be a connector to the breakerless ignition module. It is C323 on page one of these diagrams for 1976:
1973-1979 Ford Truck Wiring Diagrams & Schematics - FORDification.net
The other one I can't see the colors of the wires to tell which one it is.

 

Took some more pictures tonight of the connectors in question on the '76 wiring harness. I have taken the pictures of the connectors and with reference to the colors of wires that run into the back of each connector as shown.

First is the flat connector I am unsure of:


Second is the connector that accepts the tree prong connector from the distributor (at least this is what I assume since they match up):


Third is the other connector that ends near the distributors that I'm not sure what it is supposed to go to:


I am still unsure of where the first and third connectors are supposed to go. The first flat connector I thought went to the coil/temp/oil pressure sender but I'm missing the part that would attach to the coil. The last connector show I have no idea what it is for. Am I still missing part of the harness? Anyone familiar with the '76 wiring that can help me with this?

Here is a picture of the truck I am working on:

 

I think you might be missing part of the harness. I just looked at the schematic, and it shows the first one as some sort of generic connector. It looks like it just ties in the main harness to the dist. The third one is what I said it was earlier. It goes to the ignition module. My guess is that you don't have the right module or are missing part of the wiring.

If you look at the schematic and strip some covering off your harness (the black stuff) you can trace the colors and see where they go.

 

Thanks for the response. The first connector (flat one) does not appear to run to the distributor; it is the middle one that matches the distributor connector (unless I am missing something from this section of the wiring which is totally possible). Can anyone with a '76 (should be 76-79 I believe) wiring harness take a look for me to see where these connectors lead on their harness?

 

Can anyone with a 75-79 (after points ignition) take a look at their stock wiring that runs from the firewall towards the front of the engine and verify what my three connectors are supposed to go to? Also, needing to see if I am missing any parts of this wiring. If anyone can take a look and possibly take a few pictures of this area with the air cleaner removed I would appreciate it!

 

Finally had some time to sit down and do a little digging into the wiring diagrams Ted's link provided. The first flat connector is connection number 220 near the firewall. The third connector appears to be 320 (although I feel they have this connector location wrong, they list it as being on the L.H. Fender apron, should be near firewall or distributor). Both of these are on page 1 of the wiring diagram.

The second connector is shown on page 2 and is number 327. When hooked up It shows this connectors wires going to the throttle actuator, distributor modulator ambient switch, and distributor vacuum control valve. I have no idea what these are, what purpose they serve, if they are on my engine, or if this plug even needs to be connected. Can anyone help me with this? Also, I believe I am definitely missing the section of harness that run out from connector 220 and 320 (goes to the distributor, coil, oil pressure sensor, and temp. sensor). Does anyone have this section of the harness they would sell? This is the last piece I am needing before I can try firing the truck back up!

 

JeepScrambler, I replied to your question. I do have one, pm me and I will get it out to you

 

Sorry I was away. If you can wait, I will take a look at my truck this weekend and see how it compares. Each year is slightly different

 

On my truck, the black-green-purple-orange one connects to the duraspark module. I can't find the 3 wire connector on my truck.

I am thinking your retaping combined wires that don't exactly run together. Hope this helps some.

 

Ted, what year is the truck you were looking at for the wiring? I did re-tape the harness but kept everything as close to original as possible. My original '74 harness didn't have the 3 wire connector either. With the truck now having a '76 harness, according to the wiring diagram, I believe the 3 wire connector goes to the throttle actuator, distributor modulator ambient switch, and distributor vacuum control valve. I have no idea what these are, what purpose they serve, or if they are on my engine. Does anyone with a '76 have these parts on their truck? Sounds like some sort of emissions components that my '74 390 V8 doesn't have. Anyone have some insight to on these components?

 

I looked at my 79. The problem with these trucks is that each year is slightly different. I had a 74, and it was different than the 79. Neither of these wiring harnesses are the same as the 76. I am hoping someone with a 76 will chime in and tell how theirs is wired.