Wiring Harness (Painless)
Click to Enlarge

Quick & Dirty Engine Wiring: If your itching to test fire your engine, you can do it without installing the Painless Harness. All you need is an ignition control box & coil, along with a temporary circuit for the fuel pump. I used the MSD6al which seems to be pretty popular and comes with a built in rev limiter.

If you are going to try this, you have to have a battery cut-off switch installed, which is going to act as your ignition switch, and you will need a starter switch. I used a push-button type switch that I was going to use on the dash - just temporarily wire it so that it bridges the two larger starter relay terminals.

MSD recommends that you mount their ignition box upright, away from a direct heat source (like the engine) and not in an enclosed area such as a glove box. Since I will not be installing a heater, glove box or windshield wipers, I mounted mine on the passenger side of the firewall.

The Painless harness does not come with a dedicated circuit for the fuel pump, so you can use one of the other circuits or purchase their fuel pump relay - which is what I did. I also bought their fan relay, which comes with a temperature sensor that mounts in the intake manifold to turn the fan on & off automatically.

I did not want the mounting screws from the ignition box to go through the firewall, so I bought a piece of sheet metal from Home Depot. The right side is fastened to the upright 3/4" tubing and I put a 90 degree bend in the left side so that I could attach it to the side of the dash hoop support. This left a 3/4" gap behind the panel for the wiring and insulation that I added later.

I mounted the starter relay underneath the 2x2 frame, centered on the aluminum panel. One thing nice about mounting it there is that you can use it as a "junction box" . Since the battery is mounted in the rear of the car and is connected directly to the starter relay with a 4 gauge cable, anything that requires a direct connection to the battery, can be connected here instead. (main power leads from the Painless Fuse Block, MSD Ignition, Fan & Fuel Pump Relays and the output from the one wire alternator)

This is the starter button that I was going to use on the dash, but later decided not to. It is also made by Painless, and I did use it to temporarily start the engine. I connected the two wires to the two large terminal on the starter solenoid relay. With my main battery cut-off switch in the on position, the MSD box and fuel pump would be energized. When I pushed the button, the engine would crank - and hopefully run. To shut it down, I turned off the battery disconnect switch
This is normally how everything gets wired up.

This is the complete Painless 12 Circuit Wiring Harness that comes standard with the FFR Carb Kit.

Here is a link to their On-Line Manual

Another look at the fuse block and all those wires...

First thing you need to do is to mount the fuse block.

I wanted to mount it where it would be easy to get to, yet would not hang down and possibly injure your legs in case of an accident. So, I took the bracket that they give you and made some 90 degree bends to the ends. I had some left over 1/2" aluminum fuel line which I flared for better support and used it as spacers. I bought the nuts and bolts at Lowe's.

Here is how it looks installed. The portion of the frame where I have bolted the two tabs is called the "windshield frame mount bracket". There are two large holes in this bracket - which will be used later to mount the windshield arms. I didn't realize it at the time, but when I had both of the tabs bent downward, the one closest to the front of the car was in the way, and I had to later rebend it upwards so that it would not interfere
Here's the completed installation. All the flashers and fuses are easy to get to and easy to read. Also, I made sure to have enough wire coiled above so that I could pull the fuse block down to work on it if I had to.
This is what it looks like from above. I spent a lot of time trying to identify and label all those wires - but if you read on, I came up with a better way...
This is another pic of the fuse block, and I wanted to show where I mounted the "Maxi Fuse" - which is the main fuse. If this blows, your in trouble :(

I didn't find the Painless manual to be very helpfull - it leaves a lot to your imagination, and is written in pretty generic terms so that it can be mounted in a number of different cars. I was getting all hung up on Sections:   Headlight section A, Accessory Section B+, Ignition Switch Section, etc etc.

Here is what I came up. Basically, you are going to be running wires to four different parts of the car. The pic above is a pretty good start on which wires need to be run where. Since I am building a pretty basic car, you will probably add to it, but this is a good starting point.

This is how I rough wired the "Front" harness. About the only wire you will need to connect for now is for the Fan. I left the other wires coiled and zip-tied like that for months. Here is what was included:

  1. Fan Relay - Gray & White #901
  2. High Beams - Lt Green #908
  3. Low Beams - Tan # 909
  4. Horn - Green #924
  5. Right Front Turn Signal - Blue #925
  6. Left Front Turn Signal - Light Blue #926
  7. Front Parking Lights - Brown #927

This is how my final wiring looked. I ran the front harness through the 3/4" tubing, but if I had to do it over again - it wouldn't be worth the effort. There is plenty of room above the F-Panel, even when the splash guards are installed, to run the wires along the side of the tubing.

The wires for the right front lights run across the top of the radiator and then down along the tubing like it does for the left front. I will go into more details in Step 47.

I ran the "Engine" harness down and out the hole in side of the footbox - that is underneath the 2" x 2" frame rail. I then draped it across the engine to the other side, to get it out of the way. Since I used Smith's guages with mechanical senders, I did not have a lot of engine wires running from the fuse block

  1. Alternator Input - Red #915
  2. Main Fuse Block - Red #916
  3. Electric Choke - Red #954
  4. Starter Wire - Purple #919

This is my final engine wiring. I wanted to solve two problems. First, you will see the tube for my mechanical water temperature guage. This tube is filled with a fluid to conduct the heat back to the guage and can not be bent very sharply. Secondally, I wanted to run my engine wires so that they would be hidden from view as much as possible. I am using the FMS Cobra air cleaner which is oval in shape. The back of it extends underneath the body by the windshield and it is just a little wider than the carb.

I decided to run the wires and the sender tube underneath the air cleaner and through a hole near the top of the firewall, which makes it very hard to see.

Here is another view looking straight down. You will see the sending tube running across the top of the carb. The MSD wires for the distrib run down the back of the carb, underneath the Air Gap manifold and come out the front. Not a whole lot you can do with the alternator wire - it just runs alongside the valve cover
Next is what I call my "Dash" Harness. I am showing you this pic because you need to think about what switches, gauges, etc you plan on using - and, where they will be placed.
To organize things a little better, I ran the "Front" and "Rear" harness to the dash area. I also had a bundle of wires that I would not be using - such as the AC/Heat, Wipers, etc that I ran here just in case I needed to use them in the future. Lastly, I separated the ignition wires into its own bundle and ran them directly to the ignition switch. I made another panel to mount the wires and relays to so that the screws wouldn't show through the firewall and it also left me room for insualtion behind it.

To make the dash a little more easier to install, I planned on using some connectors in these areas. This helped in planning on where to run my dash wires to.

If you look closely you will see a bundle of wires that run along the top of the 2 x 2 frame rail. These are the power leads for the MSD, Fuel Pump & Fan relay. They run into the pedal box area, out the hole for the engine harness and get connected to the starter relay. These are the first wires I installed - before the Painless Harness went in, so I could start the engine. Note - the fuel and fan relays come with their own circuit breakers.

This is the rough wiring of the "Rear" harness. I ran the wires out the same hole as the engine harness, down along side the battery cable and then followed the cable back to the battery. I then went over the top of the battery and straght back to the center of the 3/4" tubes which make up the rear of the car. You can also see my temporary wiring for the fuel pump. You will probably not need to hook up anything in the rear harness until you are ready to wire the lights. I just coiled and zip- tied them where you see them.

  1. Tail Lights - Brown #929
  2. Fuel Sending Unit - Pink #939
  3. Dome/Trunk Light - White # 945
  4. Right Rear Turn Signal - Green #948
  5. Left Rear Turn Signal - Yellow # 949
  6. Brake Lights - Orange # 950
Final Rear Harness wiring.

In this pic, I am trying to show that Painless has already routed some of the wires for you. For example, they have wires for an electrical temperature sender which runs from the engine to the dash. Since my Cobra was a pretty basic car, I did not need a lot of these wires and they just added to the confusion.

So, I ended up cutting out all the tie wraps that Painless installed, and stripped my harness down to just the wires that actually connected to the fuse block. From that point, I could add a circuit, made sure it worked and go on to another one. It sure simplified things for me.

Note - several of the wires are always hot, such as the headlights, brake lights, etc. Be carefull with the ends of them when you have the harness powered up or you will be blowing fuses at the least...

This is what the back of the fuse block looks like once you cut all the factory bundles apart. Most of these wires will run directly to different parts of the dash, so I bundled them togethor:

To and from the Ignition Switch:

  1. Red 934 - Outgoing power to the Ignition Switch
  2. Red 934 - Outgoing power to the Ignition Switch
  3. Pink 931 - Incoming from the switch for the COIL Fuse
  4. Brn 932 - Incoming from the switch for the RADIO Fuse
  5. Org 933 - Incoming from the switch for the Wipers, A/C Heat, Fan & Turn Signal fuses.

Lights, Instruments, Horn, Switch, etc:

  1. Red/Blk 928 - is for the Headlights (always hot)
  2. Gry/Wht 906 - I used this to power my Fan & Fuel Pump Relay
  3. Pink 920 - I used this for switched power to the MSD Box
  4. Org 959 -is for the Parking / Tail Lights (always hot)
  5. White 945 - is for any Interior Lights (always hot)
  6. Brn 951 - is for the Hazard Lights
  7. Red/Wht 935 - is for the VoltMeter & Fuel Guage
  8. Purple 952 - is for the Turn Signals
  9. Black wire (no number) - is the ground wire for the Horn Relay

These are the wires that I did not use - but I still ran them to the dash in their own bundle, just in case::

  1. Blk/Wht 904 - for A/C Heat
  2. White 914 - for Alternator Excitor ( I used a GM 1 wire)
  3. Blue 905 - for Wipers Red 940 - For Radio (always hot)
  4. Red/Blk 941 - for Radio (switched)
  5. Org/Blk 955 - for 4 wheel drive switch

Lastly, you have these wires:

  • Red 915 - Engine Harness to Alternator
  • Red 916 - Engine Harness to Starter Relay
  • Red 954 - Engine Harness to Electric Choke
  • Grn 924 - Front Harness to Horn (always hot)
  • Org 917 - to Brake Light Switch then Rear Harness (always hot)
Here is a complete breakdown of all the wires for reference
Don't forget the clutch safety switch. This will prevent the engine from starting unless the clutch is depressed. I bought a new one from a Ford dealer but it is designed for one of the Ford Factory connectors, which I did not have. So, I just cut the sides off, soldered on my wires and sealed it up with hot glue.