Wayne Cook
November 1, 2000

Step By Step

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This is the ECM (engine control module) or computer. It’s the heart of the system, and controls all aspects of engine function. Notice on the backside the numerous electrical connector pins that lead out to the harness. This unit will be mounted someplace inside the car, and must never be exposed to water.
This shot shows the plug that goes into the back of the processor. Held in place by a bolt that goes into the back of the ECM, there are 60 separate connections in this plug.
Shown here is the main EFI harness ready to go into the car. Almost everything else having to do with engine management connects into this harness at some point.
Behind the main harness, the next largest is the engine/injector harness. It will connect the fuel injectors to the system as well as many other important engine sensors and sending units.
Before you order any wiring, you need to determine what alternator you’re going to run. Shown here are the two types most commonly used. Compare the unit you’ve got to the photo seen here. The 90-amp alternator is shown on the left, while the 130-amp unit is shown on the right. Both use different types and numbers of connectors.
Shown here is the harness used for the 130-amp alternator. Notice how the 130-amp unit requires three connections. This is the way to go if your car has a big stereo or lots of power accessories.
The 90-amp alternator is quite adequate for an EFI application, but should be considered a minimum figure. The harness for the 90-amp unit has only two connections.
Oxygen sensors play an important role in telling the computer how to manage engine function. The short harness shown here leads from the O2 sensor on the exhaust pipe or header to the main harness.
You’ll need a pair of oxygen sensors like the ones seen here. The special bungs will be welded into place on your exhaust to suit your application.
Your O2 sensor installation might look something like this. You don’t want the sensors too far away from the engine. There must be no leaks in the welding around the circumference of the bung.
This harness is for the inertia switch. This switch stops fuel flow in the event of an accident. It is mandatory equipment for your street-driven, fuel-injected car.
Here’s our inertia switch mounted next to the fuel filler neck in the trunk of our car. It must be hard-mounted to sense any impact. You don’t want the switch to be cushioned in any way when it is positioned. Mount the switch in an easy-to-reach place so it can be reset easily if tripped.
Shown here is our electric fuel pump in position. These externally mounted pumps are great because you can use the fuel tank you’ve got. Here, your hot lead is set up so it can be interrupted by the inertia switch arrangement. Your fuel relay underhood is where this all starts.
Our car has a Lentech AOD transmission, and we will use this lead to control the neutral safety lockout and reverse lights.
Those of you going with a manual transmission will use a pigtail similar to this one for your safety functions. They are not interchangeable, so keep this in mind and specify manual or automatic when the time comes to order.
Another important variable you’ll need to consider is which type of starter you’re going to use. Shown here is the hi-torque mini-starter available from Ford Racing Performance Parts.
This photo shows the standard-size starter we’re all familiar with. Notice how the cable requirements for the two different starters vary. If your car has a mini-starter, be sure to specify before you order your wiring.
In this photo, we see an EGR solenoid and two sensors: a TAB (thermactor air bypass) and TAD (thermactor air diverter). The TAB and TAD sensors function in emissions management, and we won’t need them on a ’67 car. The EGR (exhaust gas recirculation) solenoid will work in conjunction with the EGR sensor and valve, which are both mounted on the throttle body. The solenoid will be mounted on the firewall directly behind the throttle body.
Here is a brand new BAP (barometric atmospheric pressure) sensor. The plug to receive it is on the main harness in front of the driver. The sensor will mount underhood on the shock tower.
This used coil came from a ’90 5.0 Mustang. You’ll need the included bracket to mount the coil on the older car.
This HEGO relay is used to handle the extra power found in the modern EFI wiring. The function of this relay is to protect the original ignition switch from overload. The twin heated O2 sensors alone draw 6 amps at startup, too much for the early switch. The early switch had to supply power only to the coil.
We’ve covered just about everything you’ll need to complete your installation. Some other optional things may interest you while you’re doing this job. Shown here is a fuel-interrupt security harness with key. Take the key with you, and there is no way the car will run.
Those of you starting with the earlier-style speed density EFI setup can easily switch over to mass air using this jumper harness.
Those going over to serpentine accessory drive on their vintage cars can use this idler setup to eliminate the smog pump and still use the standard serpentine belt. The plugs are for the ports on the rear of the cylinder heads on certain models. These ports will need to be closed off when the smog system is bypassed.
After doing a careful inspection inside your car to be sure there are no interference problems, use this WF template to create the proper-size hole in the firewall for your main harness. Be sure to check things like windshield wiper operation, etc. before cutting the hole.
We’re in the thick of it now as the main harness goes through the firewall. On this car, the best location proved to be on center directly behind the engine. On most Mustangs, the hole can go off center to the passenger side. This makes routing the wires easier and will allow you to stash the ECM in the glovebox.
We’re making our plug-in connection straight away here, and we’ll be mounting our processor under the dash using a special bracket that we fabricated with thin sheetmetal.
Take a little time to route your main harness carefully. Keep away from obvious dangers like exhaust components, etc. Complete this ground connection right away so you don’t forget. We forgot one time and went nearly bald trying to figure out why things weren’t working, only to discover this little wire hanging loose behind the engine.
Big connections are easy because the plug configuration dictates what goes where. Here, we make our connection between the injector/engine harness and the main harness.
Route the injector harness carefully and make your connections to the fuel injectors as seen here.
Other connections to be made on this side of the engine include one to the distributor. The distributor shown is a stock Ford EFI unit.
These two leads go to the engine oil-pressure sending unit and also to the water-temperature sending unit. Sending units go to gauges while sensors send information to the computer.
This plug will go to our new BAP sensor, which we’ll mount on our driver-side shock tower.
Each plug is different, so it’s hard to make a mistake in doing these connections. Here, we connect our gauge cluster wiring to the main harness.
This shot shows the rest of the instrument or gauge harness. Our technician is pointing to the factory grommet, which seals the wires as they pass through the firewall on their way to the instrument panel.
The stock coil bracket will come in handy when the time comes to mount your voltage coil. Be sure to mount the coil close enough to the distributor so that the coil wire will reach. You don’t want to mount the coil on the engine.
On the other side of the engine, you’ll need these two relays. One is for fuel pump and the other is AC/WOT. This abbreviation stands for air conditioning/wide-open throttle. The function of this relay is to disengage the air-conditioning compressor when the gas pedal is on the wood. This way, all available power goes to the rear wheels in an emergency situation like passing. These relays will be mounted on the shock tower. Windsor Fox also offers a heavy-duty relay for those running bigger-than-stock fuel pumps.
The time has come to lower our upper intake manifold into position. This good-looking, high-performance induction setup comes from Trick Flow.
Our installation is almost complete, as we’ve got our throttle position sensor connected. Here, the EGR sensor goes on line.
The induction tube is shown in place in this photo, and the connection to the mass air meter is being made. It won’t be long before we’re ready to go with this engine.

We’ve got nothing against carburetors, and they are the fuel-management system of choice for most of us. They are simple, easy to maintain and, of course, were original equipment on our vintage Fords. But when the time comes for a really great performance upgrade, we think it’s hard to beat a Ford EEC IV (electronic engine control) EFI setup. Electronic fuel injection will improve your car’s driveability instead of degrading it as a larger cam would, for example. With an EFI setup, fuel economy will improve. Instead of using more fuel, your engine will become a fuel miser, delivering far better mileage and better street performance. At cruise night, few things look cooler when you pop open the hood on a ’65 Mustang and find the Ford GT-40 intake “bundle of snakes.” Folks are going to know right away that there’s something above average about your car.

In past articles, we’ve looked at fuel injection in many ways. With the hard parts on our engine, the real challenge comes in figuring out how to wire the whole thing together. The truth is that while there are a number of components you’ll need to get things running, the chore isn’t as difficult as it might first appear. You’ll need to remember that all wiring harnesses ranging from ’86 to ’93 are different. You cannot intermix wiring from different years into one car. If you send your wiring harness into Windsor Fox Performance Engineering, they can identify what you have and what you’ll need to make your setup work. Once any confusion is eliminated, the rest is fairly straightforward.

If you’ve been following our ’67 Fairlane project car, you know our Coast High Performance 331ci stroker is down on the mounts and ready to be wired. In this short space, we’re not going to talk too much about wrenching, but rather what parts are needed to do a Ford EEC IV setup and how everything hooks together.

The good news is that the Ford equipment is “common sense designed” with plugs and connectors that fit only one way. Harnesses are grouped according to separate functions, and often differ when the components differ. For example, if your car has a 90-amp alternator, the alternator harness for the 130-amp unit won’t fit, so there is no way to get the wrong harness installed with the wires crossed. The same is true of the starter harness for differing starters.

The truth is that the EFI wiring experts at Windsor Fox have the EFI game down to a science. While WF specializes in turnkey EFI conversions, the company also sells or modifies EFI wiring harnesses as a mainstay of its business. You can buy a “no brainer “ harness from WF or have them modify yours. We took our ’67 Fairlane to WF to see what’s involved in getting the correct components gathered and then installed. It’s an interesting chore, so please follow along.