Installing a 5.0 EFI Engine In an Early Bronco

Note: These directions are not complete. It is assumed that the reader is already familiar with automobile repair. This FAQ is currently being updated, and when I have completed my 351 swap will also include details regarding that procedure (unless Ken has something already written?). The version you see here was written by Joe Monroe ( and originally appeared in the Early Bronco Registry.


You may want to check out the parts list before you start. Make sure you have everything at hand.
  1. Remove the old Bronco Engine, but do not remove any of your Bronco Wiring.

  2. Remove all throttle linkage from the fire wall and the throttle peddle from inside the vehicle.

  3. You will now need to decide if you going to use the Mustang of the original Bronco engine's water pump, alternator, power steering pump and air pump (if you have one) You will need an air pump on the engine to meet smog laws. At this point I have done this change over both ways. I prefer to use all the Mustang parts because all the accessory pulleys and serpentine belt are guaranteed to fit without modification. Even the air conditioning compressor (or air compressor) fit without extra effort. You will, however, need a reverse running fan and a modified three core radiator (Most four core radiators come too close to the fan blade.) The radiator modification requires moving the top radiator host inlet from the right to the left side, and the bottom radiator outlet from left to right. Many people build custom hoses, but the procedure described above is easily done by a radiator shop for usually under $50, and very clean.

    If you decide to use the Bronco parts, put both engines next to one another and remove the EFI engines alternator, air pump and bracket. Remove the A/C, power steering pump and bracket, and the water pump. the install the Bronco water pump, alternator, air pump, power steering pump and put it on the EFI engine.

  4. Two other details:
    • Mustang headers will fit if you have an automatic transmission, but not if you have a manual one. (The clutch linkage gets in the way)
    • You may find a small interference fit between two of the hood braces and the EGR valve/air conditioning service valve. A hammer will fix this.
    Clutch Bell Crank Installation (manual only)
    • The 5.0L block does not have a mounting hole for the clutch linkage. You must mount the space plate and bell housing to the EFI engine, then bolt the clutch bell crank pivoting bracket to the bell housing. Compare with your old block, and mark the 5.0L engine block where the second bolt must go. Drill and tap for a 1/2" bolt.
      This is difficult to explain in words, but obviously you don't want to drill in the wrong place. Make sure you get this right!


    For a standard transmission, install the spacer plate, fly wheel and pressure plate. Then install the bell housing.

    For an automatic transmission, install the space plate and then the flex plate.

    Note: Leave the automatic transmission and the torque converter in the Bronco. Make sure the the converter is all the way back in the transmission.

    Main Wiring Installation

    You will need a wiring diagram for your Bronco. Each year is a little different. It makes the wiring much simpler if you get the wiring harness from the same year and model car that you got the engine. You will also need the 5.0L wiring harness for the year of your engine. This is essential! If you don't get the wiring you must get a wiring diagram for the year of car you got the engine from.

    EEC Control Assembly Installation

    1. You can pick your own location, but to keep the electronics out of the engine compartment heat, it is recommended that you install the computer unit under the dash, on top of the heater. to do this remove the glove box, drill a hole between the top of the heater and the bottom of the dash into the engine compartment.
    2. From the engine compartment, make an oval hole 2-1/2" by 1-1/2" for the rubber plug and wiring.
    3. Put the EEC control wiring plug and the EEC power relay through the hole and install the rubber plug (which should already be on the harness).
    4. Mount the EEC control unit to the left of hole as far as possible to make clearance for the glove box for fuse box.
    5. Plug in the EEC control unit to the wiring plug.

    Installing the Wiring Harness

    1. In the engine compartment, mount the canister purge solenoid. (Note that you may pick your own location.) A good place is on the passenger side of the firewall. Mount the Thermactor Air Converter (TAD) solenoid and Thermactor Air Bypass (TAB) solenoid. Mount these units as close to the canister purge solenoid as possible.
    2. Put in the EFI wiring harness in the Bronco and route across the fire wall and wheel wells.
    3. Install the engine in the Bronco with all the brackets and exhaust system.

    Wiring Installation

    If you use the EFI alternator, you will need to wire in the new alternator into the Bronco system. first remove the voltage regulator from the Bronco. Do not remove the wiring at this time.

    From the EFI engine you will need the fusible links. the fusible links are on the starter solenoid, there are about 4 of them.

    Hook the wires up as follows:

    • Black w/orange wire goes to the black w/red on the Bronco.
    • Yellow w/white wire goes to the green fusible link on the starter solenoid.
    • Light green w/red goes to the Amp gauge on the dash.
    • Grey w/yellow wire from the heated exhaust gas oxygen sensor goes to the run position of the ignition switch.
    • Mount the coil on the left fender well and attach the red w/light green wire from the coil to the start side of the ignition switch.
    • The following wires are also in the harness, but their use is optional:
      • Clutch cycling pressure switch.
      • Air change temp sensor.
      • Neutral sensing switch.
      • Air Conditioning wide open throttle relay.
    • The following two are variable. Some 1988 engines with the Mass Air Sensor seem to require them, but not other engines.
      • Engine coolant temp sensor.
      • Air change temp sensor.
    All red wires to the run and start side of the ignition switch. In the wiring harness there is a group of red wires tied to one common red wire that goes to the ignition switch.

    Fuel Pump Installation

    The 1986 Mustang fuel pump (Ford part #E4ZZ 9350B) can be installed on the outside of the right frame rail under the passenger side. Note: if you have dual tanks you will need a 6 port electric soleniod valve to switch supply and return lines from each tank.

    The fuel pump relay is mounted next to the EEC control unti under the dash. From the relay the pink w/black wire goes to the fuel pump on the power side. the black wire from the fuel pump goes to ground. The orange w/light blue wire goes to the brown fusible kink. the red w/black goes to the inertia switch. From the inertia switch, the red wire goes to the red group of wires. You can mount the inertia switch at a location thaty is to your liking. The tan w/light green goes to pin 22 on the EEC control unit and the EEC IV SELF TEST CONNECTOR. The fuel pump relay is located under the driver seat in the Mustang. You will need this and the inertia switch from the trunk.

    Throttle Pedal and Cable Installation

    On the Bronco's accelerator pedal linkage rod, drill out the ball end on the rod, where the linkage through the fire wall connects, to the same size as the Mustang throttle cable. Now heat the shaft below the hole you drilled (at the dog leg) and turn it 90 degrees. Cut a "V" notch the same size as the cable so the cable will fit in the hole that you drilled. Now mount the mustang throttle cable to throttle peddle mounting bracket, squeeze the "V" notch together. Use the screws that were used to hold the rubber boot on the Mustang to mount metal plate and throttle cable to the accelerator pedal brakcet. Put the cable through the hole in the fire wall and route the cable behind the engine to the left side and put the cable on the throttle body.


    Check all fluids and turn on the ignition to run position. Check for fuel leaks eith each tank on line. You will have to pressurize the fuel injector the first time.

    Parts List

    E8FZ 12A664 A Bar Pressure Sensor
    E8ZZ 12A690 A O2 Sensor Pig Tail
    F03Z 9F472 A O2 Sensor
    E6AZ 9B989 C Throttle Pos. Sensor
    E6DZ 11433 A Relay Assembly
    E8ZZ 12A650 DB Computer
    E6PZ 12286 V Coil Wire
    E4ZZ 9350 B Fuel Pump.
    E6ZZ 9A750 A Throttle Cable
    E8SZ 6750 A Dip Stick
    E6LY 18472 C Heater Hose
    E7SZ 18472 A Heater hose
    E5ZZ 3C11 A Support P/S Pump

    Last Modified: SN 96/01/01
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